Physics | Astronomy Cast: Recent Episodes
Physics | Astronomy Cast
How big can a star get? This is a calculation made by one of the original pioneers of modern astronomy, Sir Arthur Eddington. And it’s named after him, the Eddington Limit. Now, astronomers are finding examples of giant black holes early in the Universe, calling into question some of Eddington’s assumptions. Let’s explore this fascinating concept! Why are stars sphere-ish? Why do blackholes not eat everything? Why do pulsating stars pulsate? It all comes down to work done by Eddington at the beginning of the last century, and today we're going to look back at Eddington's work and all its applications in modern Astronomy.
Show Notes* What the Eddington Limit is * Gravity vs radiation pressure in stars * Why star growth has an upper limit * How black holes accrete matter * Quasars and galaxy-scale feedback * Evidence for super-Eddington growth * Why modern observations challenge theory
TranscriptFraser Cain:
AstronomyCast, Episode 777, The Eddington Limit. Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. I'm Fraser Cain, I'm the publisher of Universe Today.
With me, as always, is Dr. Pamela Gay, a Senior Scientist for the Planetary Science Institute and the Director of Cosmic Quest. Hey Pamela, how are you doing?
Dr. Pamela Gay:
I am doing well. The howling wind is tremendous. If you hear what sounds like ghosts in the background, that is the wind, people.
That is the wind.
Fraser Cain:
Now, as usual, I can't hear it because we use Zoom to record and the modern technology has made it so, when your dogs are barking, I don't hear it. And so I'm definitely not going to hear the wind. But yeah, here we are.
Now I'm going to do something kind of mean, but it's for the best. And that is I'm going to say nice things about you, and you're just going to have to take it. Which is, you know, I think a lot of people, when they reach out to us about Astronomy Cast and they talk about like our scripts and sort of how we prepare, they don't realize that there is no script, that this is entirely off of the top of our heads, that I go in and what's nice is for me, I don't really even have to prepare at all.
Like I write the intro, which is sort of like my token donation to the cause. And I usually come up with the idea, but, you know, often Pamela has ideas that she wants to express, but then she has to prepare and she doesn't have to prepare just for whatever is going to be the script. She literally has to prepare for anything that I might ask and I don't know what I'm going to ask.
So how can she know what I'm going to ask? And so Pamela, you are amazing for being able to gather and prepare so much information. Be ready, sort of on your toes, nimble on your toes to handle whatever comes your way.
And in this case, there's going to be a lot of information about the Eddington Limit. And I don't know what I'm going to talk about. You don't know what I'm going to talk about.
You don't know what you're going to talk about. And yet you were always poised and prepared. So amazing job.
Dr. Pamela Gay:
This is a favorite topic. So hopefully I will not disappoint. Great.
Okay.
Fraser Cain:
How big can a star get? This is a calculation made by one of the original pioneers of modern astronomy, Sir Arthur Eddington, and it's named after him, the Eddington Limit. Now astronomers are finding examples of giant black holes early in the Universe, calling into question some of Eddington's assumptions.
Let's explore this fascinating concept. Okay, so the Eddington Limit. What is this calculation that Eddington came up with?
Dr. Pamela Gay:
So back in like circa 1916, that's when the paper came out. So he'd been working on this. Yeah.
This is fairly modern, but not so modern, because at this point in the history of astronomy, we didn't actually know how stars worked. Like people had realized they weren't burning coal, or they hadn't figured out galaxies existed yet. So yeah, Eddington was trying, like so many other people, to figure out what it was that allowed stars to exist.
And we were at a point in geology and paleontology that we were also realizing, planet is old. And so that meant the star had to be old, that meant stars had to be burning for a long period of time. And they still hadn't fully figured out all the ins and outs of nuclear fusion.
But Eddington started to propose, okay, so what if we have nuclear something going on in the center of a star?
Fraser Cain:
Not coal.
Dr. Pamela Gay:
Correct.
Fraser Cain:
Correct. As people were perhaps assuming, or would.
Dr. Pamela Gay:
Yeah, it wasn't any kind of chemical exothermic reaction. They knew that much. It had to be something else.
And we were starting to understand nuclear reactions at this point. And so what he proposed was something was going on, and we were really struggling to figure it out, because electrons were like, no, we won't allow this. And so they had to figure out electron tunneling and quantum mechanics and stuff like that.
So before we even fully understood the quantum mechanics that would allow the center of a star to do the things it needs to do, Eddington proposed, what if stars are balanced between light pressure pushing outwards and gravity pushing inwards?
Fraser Cain:
And like light pushing?
Dr. Pamela Gay:
Are you mad? It was absolutely amazing. And I mean, it's more complicated than that.
We have to look at what are the electron pressures involved? What are all the other atomic reactions involved? And we're still working to figure out the details of stars.
And in coming up with this idea, it was realized, well, shoot, if a star is producing too much light, it's going to overcome gravity and just blow things apart. If anything is producing too much light, it's just going to blow things apart. So there is some kind of a limit on how much energy can be presented while at the same time gravity is trying to hold things together.
Fraser Cain:
And this idea, I mean, I think even now, you know, we look at stars, we know they're in hydrostatic equilibrium and say, well, yeah, it's the light pressure that is keeping the star from folding in on itself. Explain that idea of just like even the light pressure.
Dr. Pamela Gay:
I love this. And if you ever want to see beautifully, cleanly done maths on this, Chandrasekhar put together a stellar evolution book that was published, I want to say in the 1930s or 40s. And there's copies of it still floating around.
It's a little penguin book, Penguin Publishers. And the maths for this is entirely straightforward. It is all algebra.
And so the idea is light has, it doesn't have mass, but it has energy. And energy in motion has momentum. And so when photons hit things, they transfer momentum.
And so every time you zot something with a photon, it can absorb the photon and it also has a transfer of momentum in the process. And so in the core of a star, we have all of these nuclear reactions taking place. And in the process, photons are being produced.
These photons work their way outwards and they random walk, they're transferring energy in all directions as they go, which is good because that random walk without any specific direction supports a sphere quite nicely. And because they can escape outwards, you end up with the bulk of the motion on average being outwards balanced against gravity. So in the center, you have this radiation pressure, it goes out, then you have convective zones that are supported through the old fashioned pressure laws and all these different things.
You can just work through the math for each area of the star, figuring out where do these different pressures end up dominating. And this is actually like an undergraduate homework assignment that I still remember both hating doing and really enjoying the fact that I was capable of doing it without getting help.
Fraser Cain:
But that idea, I mean, I think when you think about, say, steam rising or filling up a balloon and you sort of think about the sort of thermodynamic, the movement of the molecules bouncing into each other, that would probably, and people were probably examining this at the time and that was probably their first instinct, well, it's a giant blob of gas and the gas is hot and here's how much sort of, you know, entropy is going on. We use that to calculate the star, but no, Eddington said, no, no, it's the light.
It's the photons, not just particles bouncing into each other in the way we experience this in steam engines and things like that.
Dr. Pamela Gay:
And what's wild is it takes all of these things working together. So the light is heating the gas, there's gas pressure added. So you have light pressure, you have light transferring heat, creating gas pressure.
You have different atomic reactions going on, which are ionizing things and creating an electron pressure. And the classical Eddington didn't include all the electrons properly. And so we've had to modify the equations over the years to better and better represent what's going on in stars.
It's super complicated, but Eddington was the first person to really realize what was going on. And this is where having Chandrasekhar coming and being his graduate student made so much sense. Between the two of them, they were able to figure out and Chandrasekhar did surpass his advisor.
And this did lead to a great deal of chaos that we talked about in our episode about Chandrasekhar years ago. But the two of them together were able to explain all the different phases in a star's life and what keeps stars going the way they're going.
Fraser Cain:
So, OK, so this is kind of the limit, this hydrostatic equilibrium, but it also sort of defines how quickly a star can accrete mass to grow. Yes. So sort of help me understand this.
Dr. Pamela Gay:
So what you end up with is as stars get more and more massive, it puts more and more pressure on the center of the star, which accelerates the rate at which light is being produced. At a certain point, the light pressure exceeds the gravitational force holding the star together. And so the light pushing outwards starts to push at a rate greater than what gravity can pull inwards.
It's this balancing of forces that allows a star to start to blow things apart. It's the slow-mo version of what happens in a supernova. In a supernova, the star's core stops producing light.
You run out of balance. It collapses violently. In the collapse, you end up with new nuclear reactions going on, releasing energy, and that blasts what's falling inwards, outwards.
It's a much slower process or at least a much less violent process that goes on in young stars, in massive stars, as material tries to fall into them. But it's the exact same physics. And I love the fact that we're dealing with the same equations, just implemented in different limits for all these different cases.
Fraser Cain:
So then where does this kind of get us in the limits of how big stars can get?
Dr. Pamela Gay:
This is where we keep being like, oh, shoot, our observations don't match our equations. So we keep finding new ways that stars find to produce things that generate pressure and don't create pressure. So we think that the limits are somewhere below 200 solar masses.
And I'm going to put it that vaguely because the universe likes to keep going, no, you were wrong. I'm going to make bigger stars. How about this star over here?
Yeah, yeah. And quantum mechanics is incomplete. We know this because particles don't do what we thought they were supposed to do.
We don't know the underlying physics to the standard model. We just know the standard model is there may not even be underlying physics, which is super annoying to think about. But at some point below 200 solar masses, you are adding material to a star and it just starts blasting light to the point that it clears the area around it.
Fraser Cain:
And is that sort of separate? Like I sort of I think about the Eddington limit core first, that you're kind of imagining that you're you're adding material to the star. The star is getting hotter both in its core and at its surface.
And like the level of heat is kind of ridiculous. Like say a star like our sun, 15 million at the Kelvin, I think, at the center, while say 5,800 Kelvin at the at the surface. But you take a star like the hottest star, like one of those like 200 times solar masses, and you're at millions of degrees even on the surface.
I mean, they're ludicrous. Yeah. And and so if you try to add more material, then this thing is going to you know, it's going to its age will decrease and it's going to go through some of its phases of dying almost instantly.
Right. Because it's just but then I think where you're getting at next is that not only that, but then you have all of the incredibly intense solar wind that's coming out, all of the radiation that's coming off of the star, this is heating up the gas that's around it. You need cold gas to get a star to form, not hot gas.
But the brightest stars heat up the gas, they make ionized gas. And then that doesn't want to add to the star. So so in addition to sort of the internal limits of how big a star can get, you also have it sort of interaction with its environment, preventing additional material from falling in.
Dr. Pamela Gay:
And and this is just one of the many super cool things that happens as we we literally live in the realm where we're looking at the quantum mechanics of how atoms change as a function of temperature, pressure, and everything is balanced between these things. Temperature and pressure defines all these characteristics. And the pressure is coming both from gravity inwards and light outwards.
But some of the energy can go into ionization. And and this starts to lead to really weird things. And and I'm going to take a moment and say variable stars, we have to remember the variable stars.
Because one of the super cool things that Ennikton realized while doing this work is in a star's atmosphere, you have light going through all these different parts of the star that are at different temperatures, different pressures. And because of this, they have gases at different states. And gases in different states have different optical properties.
And one of the weird ones is helium. So helium one light goes through it. So neutral helium light goes through it.
Helium two, helium with no electrons attached is like I shall not let light pass. And an opacity means that when the photons hit a cloud of fully ionized hydrogen, it is more likely to cause pressure instead of to pass through. It acts like a wall.
So in a star, as it heats up, it hits a point as it's heating up, heating up, heating up that the helium goes from singly ionized to doubly ionized and it becomes opaque. And it's like, I'm going to expand instead of getting hotter at this point. And so you have a star's atmosphere starts expanding instead of heating up the same way.
Now, as gas expands, it cools. So as the star is expanding, it eventually hits the point where it's like, I'm going to become singly ionized again. And then the light can just pass right back through.
And so now you have a star that doesn't have the same amount of light pressure because it's now singly ionized helium and it's also cooler. And so there's less light pressure in general. And so it begins to collapse as it collapses.
It heats up and it eventually hits the point where it heats up enough where it starts to expand because it's heating. But it's also heating faster than it's expanding until it hits that doubly ionized helium again. This is the Kappa mechanism, and it's entirely driven by quantum mechanics playing an extra role with the ionization of helium.
So it's the little physics like this where things decide instead of cooling, expanding, heating, they're going to ionize and just do something completely different with all that energy. These are the kinds of things that we keep realizing we've left something out of our equations. And this is why stars can be bigger and stuff like that.
Fraser Cain:
You just talked a mini episode about variable stars into this episode.
Dr. Pamela Gay:
I did. I hid variable stars in the episode.
Fraser Cain:
That's amazing. All right. So now I think we need to kind of pull this all together, which is when you take this law, this limit, and use this to calculate how stars grow in the early on in the early universe.
And then you can kind of apply this to the growth of black holes. You get a certain sort of limit for how big a black hole should be.
Dr. Pamela Gay:
And to be clear, the limit is not the feeding of the black hole. The limit is the accretion disk around the black hole, which acts like a star. And so so you can sneak up on bigger and bigger black holes, but it's trickstery.
So so the situation that we're looking at is take black hole. This works for stellar mass black holes. This works for supermassive black holes.
It does not matter what size black hole you have. When the black hole is feeding, because angular momentum is a insert naughty word here, as material attempts to fly in towards that black hole, the angular momentum is like, no, you shall go spiraling around.
Fraser Cain:
Right.
Dr. Pamela Gay:
And so material builds up in a disk of spiraling material that is trying to shed its angular momentum through friction and light and other forces.
Fraser Cain:
And how this works is still a bit of a mystery.
Dr. Pamela Gay:
It's a good homework equation. Another thing I've really enjoyed, but this is a graduate school. Right.
Fraser Cain:
Right. But how this.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Yeah. I mean, just like how you can get material and how you can get, say, black holes to merge is still a bit, you know, this sort of last part of the momentum is is this is where gravity waves you're now getting rid of energy through gravity, gravitation instead.
Dr. Pamela Gay:
It's super cool. Yeah, I love this part of physics. So so you have your black hole.
You have an accretion disk around it. And as the material builds up in the accretion disk, it gets thicker and denser and has super high pressure and temperature and pressure are the two things you need to have that are high in order for nuclear reactions to start occurring.
Fraser Cain:
Right.
Dr. Pamela Gay:
And it's not identical physics to what's happening in stars other than like it's nuclear reactions the same way. But you're not going to get like the CNO cycle that is is working in the same way as in an accretion disk. It's slightly different, but also the same physics.
Right. Yeah.
Fraser Cain:
But I guess what your point is, is that this disk around the black hole generates gas is being mushed together and the temperature is increasing and is starting to behave like the interior of a star falls under the Eddington limit. Time to calculate how big these accretion disks can be around various black holes before they're too hot. They start to blow themselves apart.
The same physics is happening in this situation.
Dr. Pamela Gay:
And with supermassive black holes, the ones in the hearts of galaxies that like to be what we call quasars and active galactic nuclei. But once you start hitting the quasar side of that equation, the black holes can have accretion disks so large that they start generating light pressures that empty out the cores of galaxies.
Fraser Cain:
Right.
Dr. Pamela Gay:
At which point there's nothing there for the black hole to eat anymore. So it chows down on that accretion disk and then sits there going, I am starving. There is nothing I can do about this.
I have done this to myself.
Fraser Cain:
But so then the math, when you sort of think about it, is like you start at the very beginning. You say, OK, we've got the primordial hydrogen and helium. Yeah, we know how big a star can get.
So let's calculate the bit for the first stars. Great. That tells us the stars.
Let's say those leave behind black holes. Great. Now we know how big those black holes were.
Now the black holes try to pull in mass.
Dr. Pamela Gay:
And I need to put numbers on this because we are starting to realize that these first stars could have been between a thousand and ten thousand solar masses.
Fraser Cain:
Because now you're long. I'm trying to follow the standard line here.
Dr. Pamela Gay:
And then obviously it's not the first stars, the second generation of stars.
Fraser Cain:
But even the first, sure. But even the like, even the first stars, like like you've got hot cores, they're going to, you know, you're going to reach a limit how big the star can get. Yeah.
You know, maybe it can get bigger because it has less metal that's poisoning it or whatever. But anyway. So then you get those those first stars die. You get black holes, remnants of black holes, feed the black holes, get accretion discs. You're limited by how big the black holes can get.
But and so that defines how rapidly this these black holes can add on mass. Their accretion discs get bigger, then they can feed faster. There is a limit.
And astronomers have gone back. They've made all these calculations, string them together. They've reached the sort of the size of the black hole that you should expect at certain ages of the universe.
And the problem is the ones that we see are too big.
Dr. Pamela Gay:
Yes.
Fraser Cain:
Too massive.
Dr. Pamela Gay:
Yes.
Fraser Cain:
That they broke the rules that at some point they either violated the Eddington limit in terms of stars or they violated the Eddington limit in terms of black holes. But now we're in a we live in a universe with black holes that at some point took Eddington's careful calculations, tore them up, stomped on them and said, ha.
Dr. Pamela Gay:
Or they just found another process.
Fraser Cain:
Right. And so now, please, let's hear. Let's go through where we think the universe has potentially violated the Eddington limit.
Dr. Pamela Gay:
So and the Eddington limit is is limited to this is what happens when gas is doing the infalling. And it's because light pressure can push on gas, but light pressure pushing on bigger objects is is going than atoms and gas particles and dust particles is going to have a different kind of effect. So when you start looking at two black holes merging together, the Eddington limit plays a different kind of role.
And also with accretion disks, if you look at the situation of supermassive black hole feeding on the gas and dust around it, feeding on the gas and dust around it empties its area. Now, you merge two galaxies together, you rearrange where all the dust, dust and gas is, and you get to start over. Now, where we start running into problems is we expect all of these things to have time scales.
And the time scales are like, nope, you haven't had enough time in the universe. And we keep finding this over and over and over. So we need to figure out how to reset the time that it takes for things to happen to be different.
And and this is where like new research just in the past few months, I think time has no meaning. It still has no meaning.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
Is starting to point towards the first generation of stars were far more massive than we had envisioned. And they're actually starting to come out with, well, if you make it this big, you get this chemical ratio. And we actually see nebulae filled with that chemical ratio exactly as expected at less than a billion years of of the universe being in existence.
Fraser Cain:
Right. And so it might be that if you have that first star, just hydrogen, helium, no metals. Right.
They're able to get much bigger.
Dr. Pamela Gay:
We know that is true. And it's true because you don't have all the additional lines that electrons can go into to change how light is held back. You end up with with a lot more of this helium being it's opaque, self-allowing stars just get big and hot and stuff like that.
Fraser Cain:
And like you mentioned, some recent research and there has been examples of observations that have been made with X-ray observatories and things like that, where they're literally watching black holes feed at super Eddington rates.
Dr. Pamela Gay:
And that we're still trying to figure out what what did we miss? And this is where we're starting to realize, oh, shoot, you have to include electrons in ways that we didn't originally. You have to include what is the chemical constituency of the accretion disk in ways that we hadn't thought of before.
Fraser Cain:
Magnetic fields.
Dr. Pamela Gay:
Yeah. So you have to balance every single force. You have to balance every single quantum reaction and trying to figure out what did we forget.
This is where creativity is a part of science that we don't acknowledge nearly enough because it's it's one thing to go through and do our homework where we're like, let's just worry about what hydrogen and helium are doing. They're the bulk of the universe. And then you start realizing, OK, so to explain stars like our sun, you have to start including heavier atoms.
Otherwise, it doesn't work at the mass it's at. OK. And so we're getting more and more complex in a lot of cases.
But the computer power and also the creativity of the person running all of the maths sometimes means we just don't think of things or our computers aren't powerful enough for us to include all those things. Both factors are at play. There are a lot of times where you're like, shoot, if I run this the way I have it written, it's going to take four months.
So let's simplify the equations. And then there's also the human willingness of, well, I could figure out all of those atomic quantum mechanic electrons bouncing around doing their thing. And I do not want to.
So I'm going to simplify. I'm going to do this in one dimension instead of three dimensions. I'm there's so many ways that we simplify things because that makes the math doable.
And there's so many ways that we simplify things because we don't have computational power yet.
Fraser Cain:
Yeah, but you sort of hold that the most complicated field of science is magneto hydrodynamics, plasma dynamics.
Dr. Pamela Gay:
Yeah, yeah. And that's exactly what this is.
Fraser Cain:
And this is one of those problems that you have. You have magnetic fields. You have magnetic fields, you have plasma, you have moving fluids, charged particles moving like a fluid in this environment, and it is one of the most complicated things. And then it also brings aspects of general relativity and also brings on a whole bunch of quantum mechanics.
What I love about this, though, is that we, it's kind of like, you know, when you're like doing homework assignments, you've got some complicated problem that you're trying to do.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
And you do your math, but you know the answer. You go and you look at the answer key, but it just gives you one number. It just says, 45 meters per second.
And you go back in your calculation, you got 31 meters per second. You're like, how, where did I go wrong? And then you examine every single part of the calculation to get you to go, like, I know what the answer has to be.
And so I have to sort of revisit all of my assumptions and try and figure this out. The universe has told us what the reality is. The Eddington limit works very well most of the time, and yet we live in this universe that is slightly different.
And so it's those assumptions somewhere that we're off track and that, but you, but you know, you're not just like completely moving in an area where you have no idea where you're going. So it has structure.
Dr. Pamela Gay:
What's so amazing about this is when Eddington first did this, when Chandrasekhar expanded on this, when I did it as a homework assignment, we were looking at a line through a star from the center to the surface, looking for all of the places where changes in pressure and temperature changed what physics was dominant. So in the core, you have nuclear reactions. At what point as you move away from the core, does the pressure and temperature hit a limit where you switch from one mode to the next?
It's a straight line calculation through a star and it's good enough. As we now look at accretion disks around supermassive black holes, we're still largely trying to figure out how to do it by taking a cut through that disk, looking both up and down and also center outwards. So now it's two dimensions.
We're still simplifying and now because of all the rotations and because of everything else, it's no longer something you can do with pen and paper. We have gone from 1916 working on a chalkboard to 2020s working on a supercomputer and it's the exact same physics. We're just changing where we're applying it.
Fraser Cain:
Yeah. Well, it's a fascinating concept and, you know, I think we're going to see a lot of work and thanks to James Webb and other big observatories, we're making a lot of progress. So stay tuned for maybe someone coming up with the answer.
Thanks, Pamela.
Dr. Pamela Gay:
Thank you, Fraser. And thank you so much to everyone out there on Patreon who allows us to keep the show going. Rich is able to make us sound good.
Aviva is able to keep the website updated. Everything works because of you. This week, I would like to thank the following $10 and up patrons.
Alex Cohen, Andrew Palestra, Arctic Fox, Boré Andro-Lovesville, Benjamin Davies, Boogie Net, Brian Kilby, Kami Rassian, Cooper, David, Davius Rosetta, Don Mundus, Elliot Walker, Father Prax, Frank Stewart, Gerhard Schweitzer, Gordon Dewis, Hal McKinney, James Signovich, Jean-Baptiste Lemontier, Jim McGean, Joanne Mulvey, John M, JP Sullivan, Katie Byrne, Kimberly Rake, Larry Dzat, Lou Zeeland, Mark Phillips, Matt Rucker, Michael Prashada, Michelle Cullen, Name, Olga, Paul Jarman, Philip Grant, R.J. Basque, Ron Thorson, Sam Brooks and his mom, Scott Bieber, Subhana, Stephen Coffey, The Big Squish Squash, Tiffany Rogers, Tricor, Wanderer M101, and Zach Coquindal. Thank you all so very much.
Fraser Cain:
All right. Thanks, everyone. And we will see you all next week.
Dr. Pamela Gay:
Bye-bye, everyone.
Live Show
Even empty space isn’t empty. It’s filled with the quantum fluctuations of spacetime itself. Which can be measured with famous experiments like the Casimir Effect. There is a surprising amount of energy in space itself, which has led to some interesting theories about how the future of the Universe might evolve. You can't get something from nothing but sometimes that nothing is something you can get something from.
Show Notes* Universe as Wave Functions * Quantum Uncertainty * Heisenberg Uncertainty Principle * Zero-Point Energy * Casimir Effect Experiment * Vacuum Energy * Zero-Point Energy * Vacuum Energy Discrepancy * Potential Consequences of Vacuum Energy * Vacuum Energy and Space Expansion * Hawking Radiation & Unruh Effect * Inflation and Energy Levels * Vacuum Decay and Its Potential Consequences * Unknown Physics * Multiverse Collision * Speed of Collision Impact * Understanding the Universe * Potential Risks * Black Hole Evaporation * Cosmic Ray Energy * Future Particle Accelerators
TranscriptFraser Cain: It's the 365 Days of Astronomy podcast, coming in three, two, one. ♪♪ ♪♪ AstronomyCast, Episode 751, Vacuum Energy. Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know.
I'm Fraser Cain, I'm the publisher of Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute, and the director of CosmoQuest. Hey Pamela, how are you doing?
Dr. Pamela Gay: I am doing well. We have hit one of the key points in Spring. I know that once the apple tree is done blooming, it is safe to plant things into the ground.
And this weekend, the apple tree decided it would bloom.
Fraser Cain: I have completely unrelated news that has nothing to do with Spring, and that is, thank you everybody who responded so incredibly to my desperate plea for a new business model a couple of weeks ago. People were amazing, and generous, and kind, and we did it. That we completely filled the Universe Today gap in the business model.
That removing ads from the website was exactly the right move. And I now live in this post-algorithm, SEO, AI slop, business model, ad network vision of the future, where I just think about the stories that we want to cover, and then we just do it, and then that's that. It's amazing.
Dr. Pamela Gay: That's amazing. I am so happy for you.
Fraser Cain: Yeah, yeah. It's absolutely incredible. Just to, and you don't realize, I know I'm going to take another, I don't know, year to decompress, because so much, the last 26 years of my life has been, well, what will the search engines think?
What does the algorithm want? What am I supposed to do? What do I do now?
And now, I don't even look at my website traffic. I don't even think about anything. I'm curious about a story, one of the writers works on that story, and then I am curious about a different story, and that's it.
And so, we've been producing a ton of content, my brain is free and clear, and I'm really grateful to everybody who helped out. So if you are one of those people, thank you so much. You saved my business.
Even an empty space isn't empty. It's filled with the quantum fluctuations of space-time itself, which can be measured with famous experiments like the Casimir effect. There is a surprising amount of energy in space itself, which has led to some interesting theories about how the future of the Universe might evolve.
All right, Pamela, so I think we all imagine the Universe as a bunch of little particles flying around or clustered together. We imagine photons zipping through the Universe, but that's not how a particle physicist truly thinks about the nature of the Universe.
Dr. Pamela Gay: Now, the wave-particle duality of nature is one of the weirder things that we learn about in physics, and it turns out that when you want to think about the Universe, you want to think about it as a number of wave functions that are all interacting with each other. And when we have particles, when we have atoms, what we have is something that has a wavelength, that has a frequency, and it has an energy, and there is a zero-point energy to everything that defines the lowest quantized energy that is possible. And even the Universe, we think, is quantized in its very nature.
Fraser Cain: Whoa. So, again, I'm imagining this proton of hydrogen flying along in the Universe, and it's not actually a proton of hydrogen. It is a combined wave function across the entire Universe, with a probability of it being the proton that I'm imagining, but also a probability of it being somewhere else as well.
Dr. Pamela Gay: Yeah. Yeah. That's the messed-up thing.
In general, when you run the equations, things have a kind of mostly known position. Even the Heisenberg Uncertainty Principle, which we did an entire show on ages and ages ago, basically says you can either know mostly where something is or mostly how fast it is. You can't know both at the same time.
Pick what you want to be accurate about. And so we can get roughly at something's location. We can get roughly at something's velocity.
And we can totally get at its energy, we think. And it's this compilation of energies that builds up to describe our Universe.
Fraser Cain: Right. Okay. And so when you're talking about that idea of zero-point energy, are you saying that there is this theoretical bottom point, and then you could take your photon and then you could measure its probability across the entire Universe and you're going to get probability numbers and they can never go down to that zero, which means that although the photon is most likely here in the room with us today, it could be anywhere.
Dr. Pamela Gay: Is that right? It even gets more specific than that. So one of the coolest things is you can take a container and you can imagine that you have attempted to remove all of the mass from it, but because it's in our Universe, it's going to have energy in it.
And the zero-point energy of that cavity is defined by the sum of all particles that are capable of existing within that size of a cavity. And so...
Fraser Cain: Nobody ordered this.
Dr. Pamela Gay: This starts to get us to craziness where if you take... and there is an out for what I'm about to say. There is an out.
If you take all the known particles and the size of the Universe, you get to an infinite background energy, which is not something... infinities don't exist, we don't believe. They're just math.
So we have to start looking at things purely in terms of the differences in energy. So you can start to calculate what is the difference in energy between two different containers, one with inside of another one. And this kind of a thought experiment led to actual experiments looking at things like the Casimir effect.
Fraser Cain: Yeah. And this is one of the most mind-bending experiments that's ever been done, which is like proof positive that this thing that sounds too weird to be true is really true. So can you just explain this?
Dr. Pamela Gay: All right. So imagine that you have two sets of parallel plates. We're just going to make it as easy as possible.
Energy is inversely proportional to wavelength. So things that have little tiny wavelengths have really big energies. X-ray light, short wavelength, infrared light, long wavelength.
X-ray is going to blast your DNA, IR is just going to warm you up. So you have these two different sets of plates. And you look at what are the wavelengths that fit between the large ones, what are the wavelengths that fit between the small ones.
And you have tiny wavelengths between the small ones. Now, if you decrease the distance between the two closest plates, you have now increased the energy between these two plates. And this ends up causing a bulk force that affects the separation of the plates.
Now, exactly what happens depends on the geometry of a system. You have to be able to get things super close together in order for you to be able to start to see things like this. But folks working with thin films have been able to measure within 5% of what was theoretically predicted the value of the Casimir effect between thin films.
Fraser Cain: And so you get these, only the smallest wavelength fluctuations can fit within the plates. And so you've got the small wavelengths, high energy in between the plates, you've got the large wavelength. And what you get is a force pushing the plates together.
And literally you just, if you put two plates close together, they're going to want to push together closer with more force because of this detectable phenomenon. It is, it is bonkers. And it is this like one of the best pieces of evidence that shows that this is real.
So is this vacuum energy, quantum energy, like help me understand what is the distinction between those different concepts?
Dr. Pamela Gay: So vacuum energy is the energy that's just kind of everywhere. And it can vary. So the amount of vacuum energy you have between those two thin plates and the amount of vacuum energy you have in a room like the one we're sitting in are two different values.
But overall, the universe has a zero point energy that nothing can get below.
Fraser Cain: Right.
Dr. Pamela Gay: And this can be gotten at, again, the math doesn't match what we see, can get, you can get at it by adding up what are all the possible particle combinations that could exist, looking at all the different non particles. And then we have to remember, we don't actually understand how to quantify gravity. And so a whole lot of work has been done to try and say, okay, so this background energy that is absolutely everywhere that we see fluctuations, like you stick mass somewhere, that's a bunch of energy.
Clearly, you don't have zero point energy on a planet. But when you start to figure out could this zero point energy, could this background energy be what's powering dark energy? And this was like the first place people went when they were trying to understand what dark energy is.
You end up with a difference of a factor of 10 to the 140 last time I looked up the numbers. And that's kind of an obscene difference. And the only way we have to justify this extreme difference is, well, we haven't included gravity yet, which is kind of uncomfortable, but that's where we are, folks.
But at the same time, zero point energy has some super weird and extremely troubling potential consequences.
Fraser Cain: Yeah. So, so I just want to sort of go back to what you just mentioned. So, in other words, it’s not surprising or it's not completely unsurprising that when you have more space, then you have more vacuum energy because you have more space, more place to put your quantum particles and your waves.
But also then you, that could then be, have being a force. We talked about the Casimir effect. So you could then imagine you get more space, you get more force, you get more, that creates more space, you get more force, and it just continues to add this pressure into the, into the universe.
But what you're saying is, is that that's great in theory, but the, but the amount that would be measurable is dramatically different than what we find. Yeah. Okay.
So then what are some of the sort of unsettling possibilities about this vacuum energy?
Dr. Pamela Gay: Okay. So we're going to start with the least unsettling and perhaps the one that everyone is most familiar with. And that is black holes aren't permanent.
If Hawking was correct. And here the idea is that the energy that you have just hanging out in space, being energy allows particles to zip in and out of existence. These are virtual particles, again, Casimir effect, we know they should exist.
Well, if, if space has all the quantities of a particle, if it has polarization, spin, all of these things, and we believe it does, this means you can have a matter particle and anti-matter particles spring into existence. And if they spring into existence and they both have mass and mass is just a quantity, it's scalar. If they spring into existence on either side of the event horizon of a black hole, one of them can zip away while the other is trapped inside.
And the one that zips away, whether it's matter or anti-matter, it's carrying away mass.
Fraser Cain: So I'm going to do something completely unprecedented here in the show. And that I'm going to tell you that what you were describing is wrong. And that this is what Stephen Hawking put in his book, um, a short history of nearly everything.
And he knew that it was a misnomer and, and this sort of thought experiment has been debunked many times.
Dr. Pamela Gay: I read his book. I am guilty.
Fraser Cain: I know. I know. I know.
I know. And so let me take another crack at it, which is, and then we can sort of get to a more hybridized explanation. So, um, and I'm sorry to do this, but I know we're going to get emails.
Dr. Pamela Gay: I am happy.
Fraser Cain: No, no. So, so, um, observational astronomer, I trust the books I read. So we know that when we, so there is this sort of mechanism called unruh radiation, and this is caused by an acceleration through the universe.
That if you were on a spacecraft and you were accelerating through the universe, you would be experiencing a flux of these particles of these virtual particles of these quantum waves striking your spacecraft. And it only exists when you are accelerated. And it's like an increased amount of radiation that you'd be experiencing that is just coming from your interaction with space time itself.
And so we know that thanks to Einstein, your acceleration through the cosmos is equivalent to your being in a, in a gravity well, be it around a planet being around a black hole that if you closed your eyes and you couldn't tell whether your spacecraft was accelerating through the universe and experiencing this bath of radiation, or whether you were under the influence of a really powerful gravity well that is then causing you to experience this radiation.
And so from the perspective of an outside observer, you will see radiation coming from both accelerating through the cosmos and being in the presence of a large black hole. Now this can't come from nowhere. And so something has to give up the, has to give up the mass equivalent to the energy that is being radiated away by gravity wells, by objects, by mass.
And so that the thing that we experience is this, this Hawking radiation. And so it's purely based on the equivalence principle between acceleration through space time and the being in a gravity well next to space time. And the amount of radiation you experience depends on the sharpness.
But it's been theorized that even planets, people will Hawking radiate over long enough periods of time.
Dr. Pamela Gay: He lied to us with his analogy.
Fraser Cain: He admitted later that it was a rough analogy that wasn't that useful. So yeah, yeah, yeah, I know. I know.
And so you're hearing this all the time. And so now you get the comet brigade going, no, no, no, that's not, that's not true. And so, and so this, this idea of this unruh radiation is a, is sort of a much easier way to kind of wrap your mind around it.
And that gets away from the people asking like, oh, I thought that, um, you know, why is it if particles are going into the black hole, why does the black hole get less massive? Shouldn't the black hole get more massive? Well, you know, the whole point is that, that it's not about virtual particles that are going into black holes.
It is just about this equivalent that there is this effect on space time by both acceleration and mass because they're equivalent.
Dr. Pamela Gay: So the wild thing is that I now need to figure out how to wrap my head around is black holes above a certain size aren't actively getting smaller because of the amount of cosmic microwave background and other particles falling into them. So you don't have to worry about massive black holes going away as long as we have things like the cosmic microwave background.
Fraser Cain: And because there's still an influx of radiation coming from the CMB from particles dropping into them, whatever. And that you, you get the, the, the most of this evaporation, this radiation comes from the places where the gravity well is the steepest. And so that's why the supermassive black holes radiate more slowly than actually the stellar mass black holes.
And the small primordial black holes will radiate the fastest. Right. They'll go away because they have a really sharp, uh, like essentially a, a kink in their gravity.
Well, a point, a jerk, a moment of the highest acceleration.
Dr. Pamela Gay: Okay. So with that divergence aside, all right, with that divergence aside, let's continue. Okay.
So now we can get to the extremely disturbing things. Yeah. So, so one of the ways that theorists have come up with to explain the period, the epic of inflation in the first moments of the universe where the universe went from atoms sized to solar system sized in a fraction of a moment, um, is that the universe was actually collapsing from one energy level to another and that energy expanded out our universe.
Now that implies that if we aren't actually at a zero point energy, that we are, if we are at a quantized higher level, that the universe can again drop energy levels, right?
Fraser Cain: So what we think is the lowest amount of energy might not actually be the lowest amount of energy. Yikes.
Dr. Pamela Gay: And if we can drop energy levels again, that means we can go through inflation again. Yeah.
Fraser Cain: So like what you're saying is like, you would like, we all, everything is nice and everything is balanced. I'm trying to, I'm trying to think of analogies, right? And so I'm sort of thinking about, let's say an earth, you know, plate tectonics, you've got a bunch of plates that are sitting and they've reached this perfect equilibrium.
And then suddenly everything slips and shifts and you now move to a new equilibrium. But in between you had brutal earthquakes.
Dr. Pamela Gay: And it's a little bit worse than that because, Oh great.
Fraser Cain: Yeah, no. What could be worse than brutal earthquakes?
Dr. Pamela Gay: Bring it on. So, if you think about it, we often talk about how trillions of years from now, everything will be a particle fog, essentially an energy fog. And on the way to that state, our galaxy will fall into a galaxy cluster.
Everything will slowly merge, but then everything beyond that cluster that we're in will disappear over the horizon and we just won't be able to get light from anything else because it's too far away. Well, if we go through another inflation, we could have that happen fairly instantaneously at a random moment in time. And who knows what that will actually do to everything embedded in space-time.
Fraser Cain: Right. When you think about like the original inflation, it was something like everything in one, 10 to the power of minus 22 seconds, I don't know what that is, a octotillionth of a second. The universe went through a whole bunch of doublings of size.
Dr. Pamela Gay: Yeah. Yeah.
Fraser Cain: You know, imagine if all of your atoms decided they were going to go through a, or the space between your atoms decided they were going to go through a doubling several times in a fraction of a second.
Dr. Pamela Gay: This is where when the universe did this, when everything was pure energy, you didn't have to worry about atoms getting held together or torn apart. And so now theorists have to like worry about things like, so what forces are going to be the greater forces? We know that currently gravity is stronger than whatever is pushing our universe apart.
And so things that are gravitationally bound stay gravitationally bound. We know that in general, things that structurally hold devices together through electromagnetic effects. Atomic forces.
Fraser Cain: These are all, right. These are all way stronger than the forces that are trying to push them apart.
Dr. Pamela Gay: But what happens if inflation happens again?
Fraser Cain: Yeah.
Dr. Pamela Gay: Yeah. Yeah.
Fraser Cain: That, that, that your, the gaps between your atoms go through a series of doublings.
Dr. Pamela Gay: And this is where there, there are as many theories as you can stick theorists into a room and then multiply it a few times because some of those people are going to have more than one possible theory. And so we, we don't know what would happen if we aren't actually at a zero point energy. And the other side of this is the idea that there's this background energy created by the summation of all of these different wavelengths across space kind of gets us back to the idea of ether.
And that's just weird that everything goes full circle sometimes.
Fraser Cain: Right. Maybe that's, that'll be a different show. So, so is that vacuum decay, what you just described?
Yeah. Okay. Right.
And so let's say, and, and you know, the more space you have, and if this is a probability than the bigger the universe gets, that there is a higher and higher chance that this could happen somewhere randomly across the universe, that some part of the universe could hatch upon a new idea to collapse down to a lower energy state. So what would happen next?
Dr. Pamela Gay: So this is where you start getting into all sorts of people attempting to imagine things without understanding necessarily what timescales things are going to happen on. And you end up with a very similar problem with the idea of two universes in a bubble multiverse that have different physics colliding and merging. You can imagine the difference rippling through space.
And if it is slow enough, you basically see part of the universe go weird and then you die.
Fraser Cain: But it would move at the speed of light. It couldn't go faster than the speed of light. Could it?
Dr. Pamela Gay: No. But it could go slower than the speed of light.
Fraser Cain: Yikes.
Dr. Pamela Gay: Yeah.
Fraser Cain: Right. And so, so if I guess the worst case scenario is it goes at the speed of light. And so the moment that you find out that this is happening, you're undergoing inflation.
But maybe a more horrific version of that is that you actually watch the universe getting torn apart as it approaches you at close to the speed of light. Let's say neutrino speed as opposed to light speed.
Dr. Pamela Gay: Yeah. Yeah. Neutrino speed would still be hard to see.
But yeah, we don't know these things.
Fraser Cain: Right.
Dr. Pamela Gay: There's so many things we don't talk about that we don't know. We don't know how to quantify gravity. We don't know how to explain the fact that we have this fits on a grid like it was designed by a board computer programmer graph of particle physics.
It's looking like supersymmetry isn't real. Basically, folks at the LHC are now finally willing to say, look, we should have found it by now. We have not give up.
Now do string theory. So there's all these things that kind of are predicated on each other. Understanding the full nature of the particle zoo, understanding how to quantify gravity, if it's quantifiable.
All of these things fit together as a whole. And until we understand that whole, we can't fully understand the consequences of universes colliding of having the background energy level of the universe drop from one level to another through vacuum decay. Yeah.
So we are at this fabulous point of knowing questions, not knowing answers and being able to make stuff up.
Fraser Cain: So how do we take advantage of this stuff? I mean, if there's that much energy packed into every cubic meter of the universe, you know, Stargate, they had the zero generator.
Dr. Pamela Gay: Right.
Fraser Cain: How do you how do you extract energy out of the cosmos itself?
Dr. Pamela Gay: I, I'm just an observer. This isn't something we've figured out yet. I'm a sci-fi fan, but this isn't something we've figured out how to do beyond being able to say, yes, there's a Casimir effect.
It's really hard and expensive to prove it's there, but it's there. I think we're better off figuring out how to do productive vision first.
Fraser Cain: Right. As opposed to attempting to extract and who knows what kind of disastrous outcomes could come, like talk about a tragedy of the commons where we drop the universe down to. Is that the Fermi paradox?
Is that the is that the is that the great filter?
Dr. Pamela Gay: I don't think it's the great filter, but but I mean, this is one of the problems with particle physics is there's always this concern that we're going to do something profoundly wrong and many good sci-fi novels are predicated on this idea where you start to imagine the big one that I think got the most publicity is the when they turned on the Large Hadron Collider to do the Higgs boson search. There was the well, what if we create microscopic black holes that fall to the center of the Earth and begin devouring the planet?
And it turns out it's not really a problem. They eat very, very slowly. That one I did run the math for.
I was teaching physics at the time. It was far too much fun.
Fraser Cain: Right. That the science that predicts them also predicts that they will have evaporated before they even hit the ground.
Dr. Pamela Gay:
And even if they don't evaporate, which would have been cool because it could have allowed Hawking to finally get the Nobel Prize. But if you also run at figuring out he was wrong, they don't evaporate. They're not problematic.
They eat very slowly. They're very tiny. They mostly just split between atoms going high.
I'm a black hole.
Fraser Cain: The thing that I love with that whole thing was that there are cosmic rays hitting the atmosphere with more energy than the LHC is capable of producing. And so we are already in a natural particle accelerator that is greater than anything humanity has currently built, but not necessarily what humanity might eventually build. There will come a day when someone proposes a particle accelerator that is more powerful than anything that's ever been detected by the universe.
And then we are truly in unforeseen territory. And maybe that's when we destroy the universe. Thanks, Pamela.
Dr. Pamela Gay: Yeah. Yeah. Some nights, some days that seems like the correct output.
Fraser Cain: We brought this around to an apocalypse, which is your favorite subject.
Dr. Pamela Gay: It's excellent. It's excellent. All right.
Thank you all so much. Thank you for helping Fraser keep universe today going. Thank you all of you who also support CosmoQuestX and allow me to keep everything going over there.
This show is also supported by Patreon. Everything we do, Fraser, myself, this show, we're supported by you. This week, I'd like to thank the following humans.
Sergio Sansevero, Bill Smith, Brett Moorman, Jarvis Earle, Slug, G. Caleb Sexton, Andy Moore, Evil Melky, Breznik, Andrew Allen, Cody Ross or Cody Rose, rather, Brian Cook, Robi the dog with the dot, Kate Sindretto, Helga Bjorkog, Steven Veidt, Christian Magerholt, Andrew Palestra, Gerholt Schweitzer, ZeroChill, Les Howard, Gordon Dewis, Kim Barron, Katie Byrne, Masa Herleu, Alex Cohen, Matt Rucker, Andesor, Steven Coffey, Michael Regan, Diane Philippon, Philip Walker, Sean Matz, Cooper, Sam Brooks and his mom, Jeff Wilson, Matthias Hayden, Kami Rassian, Glenn McDavid, Kim Garish, Robert Cordova, David Bogarty, John Fays, Christian Golding, Frank Stewart, Time Lord Iroh, Jim of Everett, Sergei Manilov, Conrad Hailing.
Thank you all so very much.
Fraser Cain: Thanks, everyone. And we'll see you next week.
Dr. Pamela Gay: Bye-bye.
Live Show
Just a few years ago LIGO detected the first direct evidence of gravitational waves coming from colliding black holes. And there you have it. Boom! Black holes collide! But that wasn’t all we learned from gravitational waves, nor will we learn. Sure, the masses of merging black holes are nice to know, but what else can we learn from gravitational black holes?
Show Notes* Initial Discoveries and revisit to the groundbreaking detection of gravitational waves by LIGO * Beyond black hole mergers including Neutron Star Mergers * How gravitational wave detectors can observe other cosmic phenomena * Multi-Messenger Astronomy * Future Prospects including advanced detectors and space-based observatories * Technical challenges in gravitational wave detection
TranscriptFrasier Cain [00:00:50] Astronomycast episode 743, what else can we learn from gravitational waves? Welcome to Astronomycast, a weekly facts -based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I'm Fraser Cain. I'm the publisher of Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Sciences Institute and the director of CosmoQuest. Hey, Pamela, how are you doing?
Pamela Gay [00:01:11] I'm in the United States, so it's probably a question that you don't want me to answer. I'm also a soft money funded scientist, so that is definitely a question you don't want me to answer.
Speaker 4 [00:01:21] Okay.
Frasier Cain [00:01:21] Well, as a Canadian, now about to go into a trade war with you, my Canadian, sorry, my US friend, yeah, things are likewise bad.
Pamela Gay [00:01:34] Yeah, yeah. The thing that has me most concerned is the rule of law apparently no longer has any meaning in this country. There are unvetted people without security clearances that now have access to the Social Security numbers and payment history of every US taxpayer. Yeah, yeah, these are kids that are going in and installing these servers and getting access and it's just like, yeah.
Frasier Cain [00:02:15] Anyway, just a few years ago, LIGO detected the first direct evidence of gravitational waves coming from colliding black holes.
Speaker 3 [00:02:22] And there you have it.
Frasier Cain [00:02:23] Boom, black holes collide. But that wasn't all we learned from gravitational waves, nor will we learn. We'll get to it in a second, but it is time for a break.
Speaker 3 [00:02:34] February is the month of love and we all deserve a little something special. Dime Beauty is having their annual valentime sale right now where you can get 25 % off everything with code valentime. It's the perfect excuse to refresh your beauty routine or pick out a thoughtful gift. At Dime, clean is more than a standard. It's their promise. Dedicated to skin conscious ingredients, they focus on creating beauty, skin care, body care, and fragrances that are safe, gentle, and free from harsh chemicals. With Dime, you can trust what you're putting on your skin every single day. If you're looking for the perfect nighttime anti -aging cream, their TBT cream is a must try. It's packed with clean, age -defying ingredients that nourish and hydrate your skin while you sleep. But don't just take my word for it. Over 3 ,000 five -star reviews speak for themselves. Whether it's skin care, fragrance, or a little bit of both, Dime has something for everyone. Visit DimeBeautyCO .com and use code valentime for 25 % off right now during their valentime day sale. Grab your favorites before it's over. DimeBeautyCO .com.
Frasier Cain [00:03:35] And we're back. So before we get into what else can we learn about gravitational waves, can you give us like the short version of what we did learn about gravitational waves from colliding black holes?
Pamela Gay [00:03:48] So what we learned was they politely do exactly what they were supposed to do. And it's really, really good when observation and theory match, especially when they match pretty much perfectly. So what we were eventually able to figure out, thanks to a suite of really long tunnels on the planet Earth that had mirrors and detectors and lasers that allowed us to consistently measure within a wavelength, the length of that tunnel, within a wavelength of optical light, the length of that tunnel, what we learned is as predicted when large gravitational waves pass over and through our planet, our planet will expand and squish, expand and squish and squish in a way that has a decaying frequency and amplitude that matches theory for what should happen as two masses come together and then collide.
Unidentified [00:04:55] Right.
Frasier Cain [00:04:57] So, you know, this was the prediction. I mean, it goes all the way back to Einstein when he did his theories of general relativity and said that masses moving through space time that experience, what is it, a quadrupole moment should generate gravitational waves and that, you know, you had the whole LIGO group come together to try to see whether they could actually demonstrate this. Now we knew that gravitational waves, like they had already been proven thanks to binary pulsars.
Speaker 4 [00:05:32] Right.
Pamela Gay [00:05:33] So, so what had earlier been figured out by Holst and Taylor was when you have pulsars orbiting around each other, these are two high mass objects that are not symmetric and as they go around, they are radiating energy. And because the radiating energy in the form of gravitational waves, their orbits are coming closer and closer together. The period of the orbit is changing. We can measure that extremely precisely thanks to changes in the pulsar timing as the objects move to and fro and the distances, those pulses have to travel change over the course of the orbit.
Speaker 3 [00:06:15] Right, right.
Frasier Cain [00:06:16] And they were actually able to measure that, that the pulsars as they're going around each other, they are bleeding off that rotational, the kinetic energy into gravitational waves, that's slowing down their, how quickly they're going around each other and you're actually measuring those pulsar timings and it all syncs up.
Pamela Gay [00:06:40] And they got a Nobel prize.
Frasier Cain [00:06:41] And they got a, yeah, Nobel prizes all around. But, but then, you know, when they were directly observed as opposed to indirectly just by the way that the orbits are changing, again, Nobel prizes all around. And so I guess what did we learn apart from, yes, gravitational waves are a thing, what did we learn from that original LIGO detection of, of gravitational waves?
Pamela Gay [00:07:07] Well, the one original detection was like, yay, merger. We did it. What we found from their, their population statistics is that group of intermediate mass black holes that we knew had to exist out there. And we hadn't been able to, until recently to directly detect was finally detectable through the gravitational waves that were produced when they merged with other objects. We have also been able to see a neutron star mergers. And back in 2017, we had that, we've, I think, dedicated an entire episode to it, that, that event that we detected through the neutrinos, through the gravitational waves and through the light. And now we know the majority of gold comes from neutron star mergers.
Frasier Cain [00:08:00] So, so I get, you know, I was going to take that to the, as the next part in this journey, but no problem. You're just going to speed run today's episode, which is perfectly fine by me. I can keep up. And that is that, yeah, we got this, this confirmation that the, that the black holes mergers are actually happening. And then that taught us that, that yes, indeed as predicted black holes get closer and closer to each other as they bleed off this kinetic energy through the gravitational waves. And that in fact, neutron stars can do the same. And this is detectable by LIGO when you've got these gravitational waves and then you've got, you know, we got a confirmation that a certain class of gamma ray bursts correspond to that merger of neutron stars that we see the wreckage of this collision. We see gold, we see other heavier elements that tells us that this is the way they probably formed and not necessarily with, with core collapse supernova. So then we get another finding just a couple of years ago with the nanograv facility about through pulsar timing arrays, we get another detection of gravitational waves.
Pamela Gay [00:09:12] And here I want to separate very carefully two separate ideas. Individual pulsars should be sources of continuous gravitational waves. We do not have the technological ability to detect those right now.
Frasier Cain [00:09:28] Only if they're unbalanced though.
Pamela Gay [00:09:31] Only if they're asymmetric at some, some level. And we believe that they are asymmetric at some level. It doesn't take a lot of asymmetry.
Frasier Cain [00:09:39] So it is wobble.
Speaker 4 [00:09:41] Yeah.
Pamela Gay [00:09:41] So pulsars are theorized to be a source of continuous gravitational waves. That's not what we're talking about right now. What you're talking about right now is we can measure the distance to pulsars through a variety of different means, and as long as that distance stays constant, the arrival of those pulses will stay constant. And this is more precise in timing than your standard atomic clock. What the nanograv facility has been doing is monitoring the pulsations of myriad different pulsars, looking for changes in arrival time that corresponds to a gravitational wave sweeping through our galaxy and changing the distance to these pulsars. And as you look out across space, we can see three -dimensionally all these different pulsars. We understand from all of the data we have so far that gravity appears to propagate at the speed of light. Gravitational waves appear to propagate at the speed of light. And we can, if we estimate the distance to this pulsar, we estimate to one back there, we look long enough and we haven't been able to do this yet. We'll be able to see pulsar delay here, pulsar delay there. That's a wave moving through space. What we're instead seeing is over here, there seems to be differences. We're seeing a myriad of different delays that statistically appear to There are gravitational waves regularly sweeping through our galaxy.
Frasier Cain [00:11:32] And a class of gravitational waves that we're not able to detect directly, which are the results of the merges of supermassive black holes.
Pamela Gay [00:11:40] And this is where it gets so cool to imagine all the different things we're going to be able to detect someday. And I don't know if you want to get to that right now, but nanograv is probing massive objects merging, LIGO is, is observing intermediate mass down to neutron star mass objects merging each different mass of black hole as it merges a neutron star as it merges produces a different frequency and amplitude of gravitational waves. And we can get at the distance of these events through the amplitude we observe and, and the frequency tells us what was happening.
Speaker 4 [00:12:29] Right.
Frasier Cain [00:12:31] So what's interesting as well is, is Meerkat, which is this incredible South African radio telescope array recently confirmed the existence of this background gravitational wave to the universe in a fraction of the time that the original nanograph was able to do. And so you've got this independent confirmation, you know, more telescopes better, more, they looked at more pulsars for a shorter period of time and got the confirmation. So, so I think that's where we stand today in, in what we have learned from gravitational waves so far. And so now we're going to move on in a second and talk about what we can learn, but it is time for another break.
Speaker 3 [00:13:14] February is the month of love. And we all deserve a little something special. Dime Beauty is having their annual Valentine's sale right now where you can get 25 % off everything with code valentine. It's the perfect excuse to refresh your beauty routine or pick out a thoughtful gift at time. Clean is more than a standard. It's their promise dedicated to skin conscious ingredients. They focus on creating beauty skincare, body care, and fragrances that are safe, gentle and free from harsh chemicals with time. You can trust what you're putting on your skin every single day. If you're looking for the perfect nighttime anti -aging cream, their TBT cream is a must try. It's packed with clean, age defying ingredients that nourish and hydrate your skin while you sleep. But don't just take my word for it. Over 3000 five star reviews speak for themselves, whether it's skincare, fragrance, or a little bit of both. Dime has something for everyone. Visit DimeBeautyCO .com and use code valentine for 25 % off right now during their valentine day sale. Grab your favorites before it's over. DimeBeautyCO .com.
Frasier Cain [00:14:15] And we're back.
Speaker 3 [00:14:17] All right.
Frasier Cain [00:14:17] So I think we've got a good sense of what we've learned so far about gravitational waves. And so now let's look into the future, which is, I guess, what are the kinds of questions that we think that gravitational waves can give us some kind of answer and then how can we detect them?
Pamela Gay [00:14:37] It's not always what kind of questions can be answered so much as what parts of the universe can be probed. And one of the things you and I have talked about since day zero of, of doing astronomy cast is we cannot observe with light earlier than the release of the cosmic microwave background, but gravity doesn't have that same issue. And in general, it's not like we can go out and probe the gravity field of before the cosmic microwave background, the way we can probe the gravity field of a world and map out its sides. There's no fly by of the big bang that any NASA probe's ever going to do. But what we can do instead is look for the gravitational waves that are radiating from all directions from that early universe. And this could be part of this background of stochastic gravitational waves that we believe is out there. Now, the problem is there are a whole lot of different things that can produce gravitational waves. All it takes is an asymmetric object rotating and you're going to start to get gravitational waves. A planet like Mars with a big old volcano on it is going to have gravitational waves, just not ones we can detect.
Frasier Cain [00:16:06] When you drive down the road, you are generating gravitational waves.
Speaker 4 [00:16:10] Yeah.
Pamela Gay [00:16:10] And, and so all these different things add up. And, and so we talk about there being the individual gravitational waves that we get from merger events that we get from supernovae explosions, unless there is somehow this miraculously, perfectly symmetric supernovae. And, okay, I don't know how that happens, but we'll go with that. Anything rotating that isn't perfectly symmetric is going to radiate gravitational waves continuously. So you have things that explode and merge do a burst of gravitational waves that we see. You have things that are rotating and are asymmetric that are giving off continuous gravitational waves. And there's this random distribution we believe of gravitational waves that we may not ever be able to figure out what is. This is the stochastic gravitational waves in the background. And some of those are probably going to come from pre CMB, pre cosmic microwave background formation physics. Now, well, there's going to be stuff we can never figure out. There's going to also be stuff we do figure out. And this may be the one and only way we can ever get information from before the cosmic microwave background, other than by happening to see things that are fossilized in the cosmic microwave background. And we're only going to get so far with that as well. So it's, it's cool to think we still have this one pathway to understanding the early universe.
Frasier Cain [00:17:56] And what will be the sources of that gravitational wave? I mean, the term is primordial gravitational waves and, and as opposed to the background gravitational waves, they're coming from the colliding supermassive black holes and us driving our cars down the road and so on, but there's going to be this class of gravitational waves that will be visible, that would have been generated within that first 380 ,000 years after the big bang and in theory, right from the very beginning, right from, you know, if inflation happened, hopefully there'll be evidence of, of that, those gravitational waves in, in, you know, coming from that inflation event, but even if there are, I mean, would there be like large masses merging and colliding early on in the universe? Like what would be that source of those first gravitational waves?
Pamela Gay [00:18:43] So there were the very own acoustic waves traveling through the early material that made up our universe, that was creating a variety of overdensities and under densities in this essentially fluid that was the early universe. And so you didn't so much have discrete objects that were merging in, in the early universe, but you did have changes in the mass distribution over time. And there's other things that people worry about as well. Echoes essentially from colliding black holes and neutron stars that, that are out there today could be hiding stuff that I have to admit, I don't fully understand a lot of the papers. I do know that we both chased the, the, uh, there was, what was it?
Speaker 4 [00:19:44] 2014.
Pamela Gay [00:19:45] Oh, the bicep two, the bicep two, where they thought they were able to detect the, the effects of gravitational waves in the data they were looking at, and they didn't. And so we should be able to see in the cosmic microwave background, depending on what's going on, a, a essentially bunching up of material changes and how the light is being radiated. And so far we haven't been able to find that. So that leaves the next question of, can we find these ripples from how the material was clumped up and not clumped up in the early universe? Can we find the gravitational waves from that directly? And, and that's the next thing that we're hoping for.
Frasier Cain [00:20:38] And I think that, you know, people are aware of the upcoming European space agencies, Lisa mission, the laser interferometer space antenna, and that's going to be three spacecraft flying in formation, firing lasers back
Speaker 3 [00:20:50] and forth.
Frasier Cain [00:20:50] And then as gravitational waves sweep past, they will change the length of the arms and they're like tens of thousands of kilometers long. And so it will change those and they will get direct evidence of those supermassive black holes merging. That's the hope, but people have proposed versions of Lisa that have like maybe 12 spacecraft that maybe have longer arms and this is called the big bang explorer. And in theory, that that's what gets you to those, those first gravitational waves, the ones, the echoes of the big bang itself. And hopefully that is, you know, is something that we will eventually see maybe in our, in our lifetimes. All right, we're going to continue on this conversation, but it's time for another break.
Speaker 3 [00:21:36] February is the month of love and we all deserve a little something special dime beauty is having their annual valentine sale right now, where you can get 25 % off everything with code valentine. It's the perfect excuse to refresh your beauty routine or pick out a gift at time. Clean is more than a standard. It's their promise dedicated to skin conscious ingredients. They focus on creating beauty skincare, body care, and fragrances that are safe, gentle and free from harsh chemicals with time. You can trust what you're putting on your skin every single day. If you're looking for the perfect nighttime anti -aging cream, their TBT cream is a must try. It's packed with clean age defying ingredients that nourish and hydrate your skin while you sleep. But don't just take my word for it. Over 3000 five -star reviews speak for themselves, whether it's skincare, fragrance, or a little bit of both. Dime has something for everyone. Visit dimebeautyco .com and use code valentine for 25 % off right now during their valentine day sale. Grab your favorites before it's over. Dimebeautyco .com. And we're back.
Frasier Cain [00:22:39] All right. So we've talked about the, the potential for primordial gravitational waves to give us a look into the time before the microwave background radiation. What else can we learn from gravitational waves?
Pamela Gay [00:22:55] Oh man. So this is a conversation that Paul Matt Sutter is really the one. I'm just going to say any of you have the chance to ever talk to Paul Matt Sutter. He is the expert on this.
Frasier Cain [00:23:06] This is watch his videos.
Speaker 3 [00:23:07] Yeah.
Speaker 4 [00:23:07] Or watch his podcast.
Pamela Gay [00:23:08] Yeah. The dance videos, maybe not so much, but the podcasts for sure. Um, one of the things he talks about is how the early universe could have actually in essence fractured and, and these changes in the mass that look like fractures, if you were to try and draw them out, artistically could generate gravitational waves. He talks about how as the different forces split off from one another where first there was gravity and then there was the strong and the electromagnetic and weak. So strong went off and then the electroweak and the electromagnetic split apart. And as each of these things happened, the reality of our universe, and this is all happening in fractions of the first second, all of this could have potentially left a pattern through gravitational waves on the early universe. I don't know how we detect that.
Speaker 4 [00:24:12] I, I,
Frasier Cain [00:24:13] but in theory it's going to be giving off gravitational waves.
Pamela Gay [00:24:15] Yeah, yeah. And so we're at this point where things that I was always like, cool theory, dude, love it. We'll teach it. Can't observe it. I'm good with it though. We might actually be able to observe because there are people smarter than I am and more creative than I am. And I'm very grateful. Those people exist.
Speaker 3 [00:24:37] Yeah.
Frasier Cain [00:24:39] Um, okay.
Speaker 3 [00:24:41] What else?
Frasier Cain [00:24:42] I'll give you, this was your title. So what else can we learn from gravitational waves?
Pamela Gay [00:24:47] I, I got this idea from you.
Speaker 3 [00:24:50] Um, okay. Wait, what?
Frasier Cain [00:24:52] That was the title that couldn't have been the title.
Speaker 3 [00:24:54] I keep you. All right.
Frasier Cain [00:24:55] Well, I'll give you a couple more then.
Speaker 3 [00:24:56] Fine.
Frasier Cain [00:24:56] Uh, so one of the other ideas is that you had, um, cosmic strings that, that, you know, if they're, you know, one of the theories about the sort of underlying nature of matter is that, that it's made of these wiggly, jiggly strings.
Pamela Gay [00:25:11] And that theory, I'm so much of a proponent.
Frasier Cain [00:25:15] But if, and, and you can't direct them directly, but if, uh, that theory is correct, then, then those, what would have been tiny strings at the beginning of the universe would have sort of accreted more material, grown larger and could be potentially light years across and these giant cosmic strings moving through the universe, colliding, um, and causing gravitational waves. And so one of the possible things that you could detect with gravitational wave observatories is, is colliding.
Pamela Gay [00:25:48] Um, and over time we're getting more and more evidence that those suckers don't exist.
Frasier Cain [00:25:52] Just, just to be clear, because you would see them with gravitational lensing as well. And these large scale surveys haven't turned that up. So, uh, the other thing that I like is that we could use them to find aliens flying through space in their warp drives. That's right. And so in theory, a spacecraft as it is, you know, as when the, when the enterprise goes from star to star, it's going to be using the warp drive. And that's going to be going to be shifting space time. It's going to be bending space time to its will to be able to make this spacecraft go. And then in theory, that's going to cause a wake, a gravitational wave wake, um, which is pretty cool. And so, but the sort of the coolest idea about this, and this was like a paper that just came out fairly recently was people were saying, Oh, we won't necessarily be able to detect the wakes. That's like, there's not enough going on there. Um, but what we will be able to detect is the detonation, the catastrophic failure of the warp drives in these, uh, spacecraft. And so you'll have the spacecraft is going, the warp drive collapses, destroys the spacecraft, sends out ripples of gravitational waves. And that might be just within reach of what we could do with, with gravitational waves, which I think is, uh, is fantastic. So, uh, you know, you're wondering, and then the sort of last thing that's on my sort of mental list right now is that we could potentially use gravitational waves as a communications tool. So, you know, this is beyond our capability today, obviously, but gravitational waves pass nicely through almost anything. They'll pass through through planets. They'll pass through stars.
Pamela Gay [00:27:40] What don't they pass through nicely?
Speaker 3 [00:27:42] Uh, black holes. Yeah.
Pamela Gay [00:27:44] I mean, they pass through them.
Speaker 3 [00:27:47] So they'll pass, they'll pass. Yeah.
Frasier Cain [00:27:49] They'll pass around them.
Pamela Gay [00:27:50] Yeah.
Frasier Cain [00:27:51] Um, right. That a, that like when a gravitational wave passes a black hole, it will, any part of the gravitational wave that directly falls within the event horizon of the black hole gets added to the black hole. You convert the mass energy of the gravitational wave and you end up with, uh, additional mass in the black hole, but, but anything that, you know, but otherwise they get distorted. They get twisted as they go near the black hole. But in theory, if you could move a mass in a certain way, you could generate gravitational waves. You could modulate the gravitational waves. And if you have a detection system that is good enough, you could theoretically detect it. And it might very well be that, that some future advanced civilization could use these gravitational waves as a way to communicate. And in fact, that might be the best way to communicate. And so the reason we don't see any evidence of aliens out there is because they're all using gravitational waves to communicate with each other in some way that we haven't figured out yet. So, um, so there's a lot of like cool science fiction ideas on what you could use gravitational ways for.
Pamela Gay [00:28:55] What I love about doing the show is I don't generally keep up to date on all of the theoretical technology research going on, which is not my thing. Totally your thing. And, and so over the years, the show has totally become a collaboration because of all the interviews you've done with folks with NIAC funding, folks who are thinking out of the box with the technology for communications and thrust and everything else. Cause I would never have come up with those in any of the research that I was doing. I sort of hit the, uh, here are some papers. I don't fully understand on primordial, uh, primordial gravitational waves.
Frasier Cain [00:29:39] So that's the other thing is searching, potentially finding primordial gravitational waves, sorry, primordial black holes. So that there is a minimum size of black hole that should be created naturally through the collapse of a massive star and that then if we detect the mergers of any black holes that are not mergers between neutron stars that are lower than the mass of that minimum mass level, then that immediately confirms the existence of these primordial black holes. Uh, one of the things that we haven't seen so far is mergers between white dwarfs and neutron stars or white dwarfs.
Pamela Gay [00:30:20] And the frequency is wrong.
Frasier Cain [00:30:21] Well, but Lisa isn't your tool. Lisa is the one that gets us the colliding supermass of black holes. There's an extension to LIGO call. So there's a couple of extensions to LIGO and a new thing called the Einstein telescope. And that will have, so right now LIGO has arms that are a few 10 kilometers, 15, I forget the length of the arms on like that.
Speaker 3 [00:30:46] Yeah.
Frasier Cain [00:30:46] But, but the Einstein telescope will be 40. And so it'll be like the largest feasible gravitational wave observatory that you can put on earth. And what's nice is that it just blends in with the rest of the existing, uh, community. So, um,
Pamela Gay [00:31:01] did they change Lisa? Cause Lisa was originally billed as the white dwarf merger detector.
Frasier Cain [00:31:08] I, I don't, I don't think so. I mean, maybe Lisa will also be able to do white dwarfs, but it's the, it's the longer, slower mergers that they're going to go after. It's these longer baseline ground observatories, but like, like the gravitational wave observatories are kind of like telescopes. You tune them to specific frequencies and then that's what you're
Speaker 3 [00:31:28] looking for.
Frasier Cain [00:31:29] But, but yeah. So in theory, we will get these confirmations that white dwarfs collide with, with black holes, that white dwarfs collide with
Pamela Gay [00:31:35] neutral.
Frasier Cain [00:31:35] Like obviously this is happening, but that'll tell us which of the kinds of explosions that we see in the universe are matched with these kinds of mergers. So, uh, so it's a lot of things, but as soon as you move mass, then you get to observe the gravitational ways of that
Speaker 3 [00:31:51] thing.
Frasier Cain [00:31:51] So, all right. We've reached the end of our show. Thank you, Pamela.
Pamela Gay [00:31:55] Thank you, Fraser. And thank you everyone who is watching this video and apologies. I do not know why my camera decided it needed to, uh, completely lose its mind for a moment, but that is what it did. I mean, I understand. I think I've completely lost my mind for a moment, a few times over the weekend. Um, this week we would really like to thank, uh, some of our $10 or not patrons, uh, this week we would like to thank Alex Rayne, Andrew, Palestra, uh, Antasor, Astro Bob, Astro Sets, Benjamin Carrier, Benjamin Davies, Bill Smith, Bob Krell, Boogie Net, Brenda, Brian Kilby, Bruce Amazines, Manski, Claudia Mastriani, Cody Rose, David, David Rosetta, uh, Diane Philippon, Don Mundus, Frodo Tanenbe, I think I said that time, uh, Jeff, uh, McDonald Gold, Hal McKinney, Janelle, Jeremy Kerwin, Jim McGeehan, Jimmy Drake, Jordan Turner, Justin Proctor, Katie and Ulyssa, uh, Christian Magersholt, uh, Mark Schneider, Michael Purcell, Michael Regan, Nate Detweiler, Papa Hotdog, Rando, Robert Hundle, Robert Palasma, Ryan Amory, the Air Major, Thomas Gazetta, Timelord Irowe, Will Hamilton, William Andrews. Thank you all so very much. You make this show possible.
Frasier Cain [00:33:29] Thanks everyone. And we will see you next week.
Speaker 4 [00:33:31] Bye bye.
Pamela Gay [00:33:38] Astronomycast is a joint product of Universe Today and the Planetary Science Institute. Astronomycast is released under a Creative Commons Attribution License. So love it, share it, and remix it. But please credit it to our hosts, Fraser Cain and Dr. Pamela Gay. You can get more information on today's show topic on our website, astronomycast .com. This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at patreon .com slash astronomycast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomycast.
Speaker 4 [00:34:36] Breastfeeding is natural, but that doesn't mean it's easy. That's where the Lactation Network comes in, a network of highly credentialed lactation consultants who provide support at every step of your breastfeeding journey. With their expert guidance, you can prepare for your baby's arrival, resolve breastfeeding issues, create a plan to wean or anything in between. The Lactation Network offers in person visits in all 50 states and is now in network with most major health plans. To see if you're covered, visit tln .care today.
Speaker 3 [00:35:06] The last thing you want to hear when you need your auto insurance most is a robot with countless irrelevant menu options, which is why with USAA auto insurance, you'll get great service that is reliable all at the touch of a button. Get a quote
Frasier Cain [00:35:17] today. Restrictions apply.
Live Recording
In our last episode, we talked about the Parker Solar Probe. As always, we like to talk about the person who inspired the mission. What makes this amazing and different is that Eugene Parker was there to watch the launch of the mission that shares his name. Why is he so influential on solar astronomy?
Show Notes* Eugene Parker's early career * Eugene Parker's contributions to the field of heliophysics * The Parker Solar Probe * Eugene Parker's later life
TranscriptHuman transcription provided by GMR Transcription
Fraser Cain:
Join Patreon for an ad-free experience at patreon.com/astronomycast. Astronomy Cast, episode 728, “Eugene Parker.” Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos where we help you understand, not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the Director of CosmoQuest. Hey, Pamela. How are you doing?
Dr. Pamela Gay:
I – I am doing well. I am super excited. On October 4th, I’m giving a talk at the St. Louis Science Center. And it’s during one of their themed events, and the theme for the night is Barbie and STEM careers. So, I – I’m going to – they – they encourage cosplay. So, I have a pink suit and a pink dress. And – and I’m, uh, going to have – my first slide says, “My job is space.” Um, and I’m gonna talk about all the women throughout history who, uh, have basically done groundbreaking work while being citizen scientists. Um, yeah. So, I’m super excited about that.
Fraser Cain:
That sounds great. Um, so, I am also excited. I – I haven’t mentioned this to you, Pamela, yet, but, um, I’m gonna be taking a trip after we record next week. So, I’ll be here next week but then I’ll be gone. I’m going to, uh, Europe for –
Dr. Pamela Gay:
Oh.
Fraser Cain:
– eleven days with my kid.
Dr. Pamela Gay:
Okay.
Fraser Cain:
So, the other kid. And so, I took my first kid to Japan, and now I’m taking my second kid to Iceland and Amsterdam. And so, we are gonna be in Iceland for three nights and then we’re gonna be in Amsterdam for the rest of the time. Early October –
Dr. Pamela Gay:
Does that mean we need to record two episodes next week?
Fraser Cain:
Maybe. But, you know, – or maybe I can record them while I’m afar. Maybe. We’ll figure that out. Um, but – and the goal is to see the auroras, to – to be able to be in Iceland and actually watch as we increase toward solar maximum. So, I’m pretty stoked and, uh, I’m looking forward to going back to Europe.
Dr. Pamela Gay:
Amsterdam is one of my favorite cities. If I was –
Fraser Cain:
It’s such a great city.
Dr. Pamela Gay:
– offered a job in the Netherlands I’d move in a heartbeat.
Fraser Cain:
Yeah. So, last week we talked about the Parker Solar Probe, and as always, we like to talk about the person who inspired the mission. What makes this amazing and different is that Eugene Parker was there to watch the launch of the mission that shares his name. Why was he so influential on solar astronomy? So, this is – you were quite excited about this –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– when we were talking about the Parker Solar Probe and you were like – and you often would say, “And by the way, he’s still alive. Isn’t it so adorable to watch him there at the launch site watching his spacecraft take off.” So – so – and he is passed away now but – but normally –
Dr. Pamela Gay:
He was alive for the launch.
Fraser Cain:
– normally, the people who the spacecraft are named after have been – have passed away for a long time. And in some cases, hundreds of years, thousands of years, in some cases. And yet, he was there for the launch. So, who was Eugene Parker?
Dr. Pamela Gay:
He was a physicist who, uh, – so, I’m pleased to say, we have the same alma mater. We both went to the physics department at Michigan State University. He just did it half a century before I did. Um, he was a physicist, and his work ended up opening up the field of heliophysics. It didn’t exist before him. He – he finished his undergraduate degree 21, 22. I couldn’t tell what date he graduated. Um, he then went to, uh, Cal Tech to do his PhD, which he did in three years, which blew my mind. He was then an instructor at the University of Utah for a few years before going to the Enrico Fermi Center at the University of Chicago, where he did the rest of his career.
And as a baby professor, he postulated that the sun could have a magnetic field that triggered a solar wind. And when he submitted the paper for this, the referees, one of them literally said that he needed to go to the library and read more because the paper was ludicrous. Um, the paper was soundly rejected by both referees, but the editor of the journal was Chandrasekhar, who was also at the University of Chicago, knew Eugene Parker, and he reviewed the math. He replicated the math. He could find nothing wrong with the math. So, he published the paper anyways. And – and so, that was 1957, and I have to look at my notes to get all the dates right. So, the paper was published in 1957. This was before we really had a lot of space probes.
And in 1962, Mariner 2 on its way to Venus measured the solar wind and all the people who were still making fun of Eugene Parker for his ludicrous idea, um, had to agree that he was right. And since then, the particular research paper that he published, the one that was soundly rejected with scathing criticism, has over 4,000 citations.
Fraser Cain:
Wow.
Dr. Pamela Gay:
It’s just amazing work.
Fraser Cain:
So, wait. Did he postulate the existence of the solar wind based on the magnetic field of the sun? Like, he guessed the sun would have a magnetic field and therefore to be producing a solar wind? Or was he –
Dr. Pamela Gay:
Exactly.
Fraser Cain:
He wasn’t just suggesting that the source of the solar wind was the magnetic field?
Dr. Pamela Gay:
No. We didn’t know there was a solar wind at all.
Fraser Cain:
Wow.
Dr. Pamela Gay:
There – the solar wind was not to blame for aurora yet. I now want to go back and find out what they thought caused aurora up until this point because I have no idea.
Fraser Cain:
Yep. Yeah, yeah.
Dr. Pamela Gay:
Um, but, yeah. He completely postulated the – the – like, he’s also responsible for like the solar dynamo idea for magnetism and galaxies. And we can go into detail on all of this stuff. But in the 1950s, we didn’t know there was a solar wind. He looked at the math. He looked at the magnetic field of the sun. And he’s like, “Gotta be a solar wind.”
Fraser Cain:
Right.
Dr. Pamela Gay:
And he did all the math –
Fraser Cain:
Wow.
Dr. Pamela Gay:
– to prove it from first principles. It was amazing.
Fraser Cain:
Right, yeah. And when Chandrasekhar looks through your math and gives it the green light, that’s – I mean, he – he’s the guy who figured out the Chandrasekhar limit. I mean there’s – there was a documentary about him.
Dr. Pamela Gay:
So, Chandrasekhar – and go back and listen to the episode we did on him. Um, he was also soundly knocked for some of his principles until they were proven. So, he understood that sometimes you have to wait for someone to die before your theories get accepted.
Fraser Cain:
Yep.
Dr. Pamela Gay:
And he – Parker was so lucky to have Chandrasekhar in his corner.
Fraser Cain:
Yeah. That’s – that’s incredible. Um, so, like what else? I mean, so he – he made this groundbreaking sort of prediction –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– which – which are like the best. I mean –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– when someone predicts a thing in the universe and then someone takes a telescope or a mission or whatever and goes and finds that thing, those are the – some of the most impactful sort of advances in the science that have – that are ever made. You think about Einstein’s relativity. You think about, uh, various theories about black holes and so on. When someone makes that kind of a prediction and then the technology comes along to actually demonstrate that it’s true, it really stands the test of time. So – so, what else then, you know? How did he top that? What did he – what did he then go on to do?
Dr. Pamela Gay:
[Laughs] So, every biography I’ve found of him described him using either the word visionary or a, uh, synonym for visionary. And he went on to also postulate what is now called the Paker spiral, which he was a magnetic physicist. He wasn’t – the field of solar science, the field of heliophysics, didn’t exist and his work spanned multiple areas. He was a magnetic fields physicist. So, in looking at the sun’s magnetic field, which he continued to do, he realized that the rotation of the sun would cause drag on the magnetic field. And this had – there was drag between the two of them is a better way to put it. And – and this would have two impacts.
So, one thing he predicted was what’s called the Parker spiral. So, between 10 and 20 AU out from the sun, the magnetic field begins to twist. And so, if you look at the large scale structure of our sun’s magnetic field, it actually has a spiral structure to it. It’s an Archimedes spiral.
Fraser Cain:
Hmm.
Dr. Pamela Gay:
It’s that classic shape that appears in everything from snail shells to grand designed spirals. Well, it’s also in the – the magnetic field of the sun. And on the other side of that, he realized that one of the things that is probably leading to the differential rotation of the sun where we see the equator and the northern and southern latitudes rotating at different rates was probably the magnetic field having an effect on the surface as well. So, he was able to figure out these two different major components of what the magnetic field is affecting in our solar system, both on the solar system scale and on the solar scale. And that was amazing.
Fraser Cain:
Right. And he – I mean, he wasn’t just content to work on just the sun. He took this idea of interactions between magnetic fields and plasma to many different scales.
Dr. Pamela Gay:
Yeah. He was the person who figured out that there should be magnetic instabilities in galaxies. So, when you look at a galaxy, you – you can get up and down motions in things and they also have a magnetic field due to the spinning of the material around the black hole and the core that is parallel to the disk. And because of the orientation in the magnetic field, when you get material that is coupled to the magnetic field, when you have charged materials in the disk that is moving up or down, you will get an amplification of that movement due to the interaction with the magnetic field.
So, when we see these warps in disks, to explain that we have to look, not just at the gravitational interaction of something perturbing the disk, but also the magnetic fields’ effect on perturbing material in the disks.
Fraser Cain:
And – and this idea of – of – or this technique for measuring the magnetic fields around some kind of an object, this is all really brand new. Um, –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– where you can essentially measure the polarity of the photons, the radio photons, that are coming from some object. And there’s this – this incredible work Say Done by Meerkat. I know that’s one of your favorites.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Where they’re able to scan chunks of the sky, measure the polarity of the radiation, of the radio waves, that are coming from this area. And that is because the photons have been turned into – into various directions and, you know, causing this polarity that’s visible. And you can then map out the large – Alma does this a lot as well. You can map out the large-scale structure of the magnetic field lines around what you’re looking at. And – and this whole field of predicting these magnetic fields that – that you – the way they sculpt and create galactic wide versions of the solar wind all trace back to Parker’s work in doing the math and making these predictions.
It’s absolutely incredible. I mean, you know? It’s like if they come up with a spacecraft that’s also going to search for, you know, examine the large-scale galactic winds coming off the Milky Way, they’ll also have to call it the, you know, the Parker Galactic Probe or something.
Dr. Pamela Gay:
Yeah, it’s – he was a theorist who took the ideas behind magnetic field theory and applied it anywhere there could be charged material. And the sun was something he kept returning to over and over again. The – the corona heating problem, um, was one of the things that I – I think he played with the most, uh, later in his career in 1987 in looking at the coronal heating problem. This is what we talked about in the last episode where – where the outer most, most diffuse part of the sun is like millions of degrees. Very confusing. Um, and – and he was the one who postulated that nanoflares, small breaks in magnetic field lines that are carrying hot plasma, could release sufficient energy to heat the – the corona.
And – and these are things that the Parker Solar Probe was designed to go look for. And – and all these ideas, he was always out there saying, “Hey, I’m a theorist. This is what the math says. Observers, go prove me wrong.” And that is a terrifying place to be.
Fraser Cain:
Right.
Dr. Pamela Gay:
And when he was asked to provide advice to young scientists after having this entire career of over and over again predicting things and sometimes being mocked, his advice was, and I’m gonna read the quote, um, “If you do something new and innovative, expect trouble. But think critically about it because if you’re wrong, you want to be the first one to know that.” And this was advice he have in 2018 to early career researchers.
Fraser Cain:
Oh, that’s fantastic.
Dr. Pamela Gay:
I just love that idea.
Fraser Cain:
Yeah, yeah. You – if you’re wrong, you want to be the first to know you’re wrong. Yeah, that’s so good. Um, you know, I mean that idea, the nanoflares that you mentioned, right, like, he back in the ‘80s –
Dr. Pamela Gay:
Mm-hmm.
Fraser Cain:
– did the math. Predicted that there should be these miniature flares on the surface of the sun, scaled down versions of the big bright flares that – that we see every now and then. These are happening all the time and that they were responsible for the coronal heating. And then you get the detection and measurement of these nanoflares by both Parker Solar Probe and the solar orbiter exactly as Parker had predicted. We just didn’t have the technology –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– to – to sense them beforehand. And so, I think, you know, that prediction of his that was – I’m just doing some math here. Like, whatever, 40 years old, plus, was finally confirmed by the spacecraft that bears his name. Once again, he was right.
Dr. Pamela Gay:
Did – did you watch the Parker Solar Probe launch on NASA TV?
Fraser Cain:
Yeah.
Dr. Pamela Gay:
Were you scared for him?
Fraser Cain:
I mean, he was 90 –
Dr. Pamela Gay:
Ninety-two.
Fraser Cain:
Ninety-two when it launched. Yeah, yeah. Surrounded by boisterous engineers and people clapping and, yeah, he looked pretty frail already at the time. But he was there –
Dr. Pamela Gay:
He – he was there.
Fraser Cain:
– to watch it launch.
Dr. Pamela Gay:
And what I was scared for was – so – so, once upon a time, they waited until missions were launched to rename them. So, like, uh, the Ferme x-ray satellite was Glassed up until like four days after launch when it became Ferme. Um, and – and so, we saw that over and over and over again. And then they started naming missions before they launched because that gave you more of an emotional connection and made it harder for Congress to murder them.
Fraser Cain:
The spacecraft, not the people.
Dr. Pamela Gay:
Right, right. The spacecraft. So, this was particularly important for the Nancy Grace Roman telescope. Um, but we never, except for the Parker Solar Probe, have named something after someone living. And – and as I’ve talked about in the past, I – I had a mission I needed for my dissertation blow up right after launch.
Fraser Cain:
Yes.
Dr. Pamela Gay:
And so, that haunts me. And so, like, I’m watching the NASA stream and the whole time I’m like, “Oh, god. It’s gonna blow up. It’s gonna break his heart. He’s gonna have a heart attack.” Like, this was the worst case thing –
Fraser Cain:
Yeah.
Dr. Pamela Gay:
– that was going on in the back of my brain. Everything was fine. Nicole Fox, who is head of Helio at the time, was with him the entire time. Um, and in fact, after his retirement and after the spacecraft’s launch, she continued to send him data from the Parker Solar Probe for him to review.
Fraser Cain:
Oh, wow.
Dr. Pamela Gay:
This is a man who retired but just kept doing research.
Fraser Cain:
Yeah. And we see that a lot. I mean, it’s just there’s so many scientists –
Dr. Pamela Gay: [inaudible – crosstalk]
Fraser Cain:
Yeah, exactly. The scientists, they – they – they don’t retire. They die. They just keep working. Um, so, – I mean, we – we saw the launch of the Parker Solar Probe and he was still alive –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– but, uh, – and they – they had named it in 2017 after him. But then he did pass away in 2022.
Dr. Pamela Gay:
Yeah. He was age 94. Um, he was survived by his wife of 67 years.
Fraser Cain:
Wow, relationship goals.
Dr. Pamela Gay:
Yeah, yeah.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
He had both a son and a daughter. And – and his son had some of the best stories. So, apparently, like, the kids growing up knew their dad was a scientist but didn’t really know what he did. They had no idea that he was famous at all. And apparently, he was someone that worked really hard to have a work-life balance and would tell his kids that anyone who’s working over 40 hours is missing out on life. This was someone who was very much your Great Lakes Midwesterner. He loved to camp. He – he loved to go hiking. And his hobby was woodworking. His son Eric said in an interview that pretty much all the furniture in the house was made by his dad.
Fraser Cain:
Wow.
Dr. Pamela Gay:
He was that kind of a woodworker. And he also liked to carve figures of famous people. And I tried but I couldn’t find any photos of these. And I – I really – I really wish I could because just the idea of this person, who as a scientist I hold in such esteem, imagining him sitting on his front patio. Like, who was he carving figures of that he considered to be famous?
Fraser Cain:
Yeah.
Dr. Pamela Gay:
That’s what I wanna know, um, and no one said anything bad about him that I could find. He – he was the kind of person that was described as – as humble, which makes sense with his kids having no idea what he did. He was someone who was described as willing to do and publish research that – that people didn’t believe initially. He took those risks. And so, he was constantly back and forth throughout his career of, “Oh, he’s such a visionary” and “Oh, that idea is kinda (insert negative phrase”. That’s such a hard place to be. And to remain humble while living in that kind of a dichotomy. Just – those – those are scientist personality goals. Um, yeah.
Fraser Cain:
Yeah. I mean, I had heard him described as somebody who – who was very creative, out of the box –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– thought of, you know, – understood the implications and the consequences of – of various observations to sort of figure out what happened next but then was very careful and, um, diligent in –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– in how he explored the mathematics for what that would imply and was willing to throw out – as you say, as soon as you figure out you’re wrong, get rid of it. But – and then when you balance that with that – that perspective on work-life balance on – on shunning workaholism, and instead, build a career where you’re still thinking about – as you said, you know, even when he was 92, he was looking at the results coming from – from Parker that – that it's more of a marathon than a sprint. And I think that’s really – that’s a really great way to – to live your life.
Dr. Pamela Gay:
Yeah. And – and his Dean at the University of Chicago from when he was an emeritus described him as someone with boundless energy. One of those people who just, like they always say every visionary should do on the internet. He was someone who got up super early in the morning.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
Worked, uh, with – with great – they always described him as “having amazing intuition.” And one if the – the things that I saw that was like, “Oh, that’s not quite work-life balance but I understand.” He had the kind of intuition where if he was in the middle of eating dinner and a thought came to him, he’d wander away to go write it off and then come back to the table.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
And I – I can just, like, – I know theorists like this where all of the sudden they’re off. Okay. The idea – the idea took over. And then –
Fraser Cain:
But that’s experience, right?
Dr. Pamela Gay:
Yeah.
Fraser Cain:
That’s knowing that – that if you don’t get the idea, like, down immediately –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– then it’s lost forever.
Dr. Pamela Gay:
It’s gone, yeah.
Fraser Cain:
It’s gone. And so, if you don’t capture it at that moment with enough fidelity that you can then explore it in more depth, that’s the challenge of the – of the shower thought, right?
Dr. Pamela Gay:
Right.
Fraser Cain:
That’s the problem. You’re – you’re walking along and you have a good idea and then you’re like, “Okay, this idea is so good that I’m gonna hold onto it now and then I’ll think about it later on.” And then you get home and you’re like, “What did I think of again?” And it’s gone. And you mourn it.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
And so, I think that’s – that’s just purely wisdom and experience to know, “Okay. Idea pops up. I better get it down right away. And even if I have to interrupt dinner, right, to do that.” Because you’re always digesting these problems. And I think back to that – that idea of that work-life balance. Like, I find I only really make progress on some of the more challenging problems that I’m trying to deal with when I’m in a place that is a lot more balanced. And even when I’m doing a task that’s completely unrelated. I can be out in the forest cleaning up, you know, um, brush and go, “Oh, yeah. That’s what I should do.” And then I – and then I have to drop what I’m doing and write it down immediately or it’s gone.
Dr. Pamela Gay:
For me, it’s folding laundry. All my best ideas come to me while I’m folding laundry.
Fraser Cain:
Yeah. Now, he won ever award that you can win pretty much –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– did he get the Nobel? I don’t think he got the Nobel.
Dr. Pamela Gay:
He did not.
Fraser Cain:
No.
Dr. Pamela Gay:
No.
Fraser Cain:
But he got, you know –
Dr. Pamela Gay:
Everything else.
Fraser Cain:
– everything else. He wrote over 400 papers, which is –
Dr. Pamela Gay:
Yeah.
Fraser Cain:
– just crazy. I mean, you imagine, – like, say you’re writing papers for 40 years. That’s 10 a year. That’s like – that’s a paper a month pretty much.
Dr. Pamela Gay:
So, let’s assume that he wrote papers between age 22 when he got his undergraduate degree and 94. So, that’s 72 years. That’s – that’s four or five papers, some years eight or 10 papers probably, per year and most of us aspire to average one or two a year.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
So, that’s truly remarkable.
Fraser Cain:
Yeah. Multiple books. Like, four books.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Many are used –
Dr. Pamela Gay:
Textbooks.
Fraser Cain:
– as textbooks by people who are teaching in the field. Yeah. Wow.
Dr. Pamela Gay:
It’s – it’s the correct decision that they named the Parker Solar Probe after him.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
It’s amazing that he got to be there and see it. And to be sharp enough at 94 to understand and want to be part of the research is something all of us can only dream of.
Fraser Cain:
Totally.
Dr. Pamela Gay:
He had Parkinson’s for the last 10 years of his life but his brain was still going.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
And I really am saddened that this is someone who I never met that lived and did research in my lifetime because he seems like a truly amazing human.
Fraser Cain:
Yeah, that’s incredible. Very cool. Well, thank you, Pamela.
Live Recording
Last week, we learned about the death of Peter Higgs, a physicist and discoverer of the particle that bears his name. The Large Hadron Collider was built to find and describe the particle. Today, we’ll look back at the life of Peter Higgs and his particle.
Download Now
Ice is ice, right? You know, what you get when water freezes. Well, maybe here on Earth. But across the Universe, water can be squeezed together at different temperatures and pressures, leading to very different structures. Today we’ll talk about the different forms that ice can take.
This episode is brought to you by BetterHelp. Give online therapy a try at betterhelp.com/ASTRONOMY and get on your way to being your best self.
Download MP3 | Show Notes | Transcript
Show NotesCrystallinity of the Ice (UCLA)
How to Make Clear Ice Cubes for Your Cocktails (Liquor.com)
You’re Doing It Wrong: The Guide to Making Perfect Pasta (Smithsonian Magazine)
Iceland Has Got a sparkling Ice Diamond Beach on Breiðamerkursandu (Guide to Iceland)
Centaurs (Swinburne University)
Scientists discover a new type of amorphous ice (Cosmos Magazine)
Scientists created a weird new type of ice that is almost exactly as dense as water (Live Science)
Ganymede (NASA)
Europa (NASA)
Enceladus (NASA)
Kuiper Belt Objects (Swinburne University)
An orbital dance may help preserve oceans on icy worlds (Phys.org)
Why do astronomers call Uranus and Neptune ice giants? (Astronomy)
Europa’s heaving ice might make more heat than scientists thought (Brown University)
What color is an iceberg? (NOAA)
Cat’s Cradle by Kurt Vonnegut Jr. (Goodreads)
Back to Top
TranscriptComing soon
It’s been over 20 years since astronomers first discovered that the expansion of the Universe is accelerating thanks to dark energy. And in these decades, astronomers still don’t have much evidence for what could be causing the increased expansion rate. Maybe there’s something else going on to explain it.
Download MP3 | Show Notes | Transcript
Show NotesEscape Velocity Space News (CosmoQuest)
PODCAST: Ep. 4: The Search for Dark Matter (Astronomy Cast)
PODCAST: Ep. 11: A Universe of Dark Energy (Astronomy Cast)
The Dark Energy Survey
The Nancy Grace Roman Space Telescope (NASA JPL)
South Pole Telescope (University of Chicago)
Physical Review Letters (APS)
Hot new early dark energy: Towards a unified dark sector of neutrinos, dark energy and dark matter (Physics Letters B)
Casimir Self-Interaction Energy Density of Quantum Electrodynamic Fields (Physical Review Letters)
Dark matter (CERN)
Dark Energy (Hubblesite)
Doppler Shift (Swinburne University)
Equation of state (cosmology) (Wikipedia)
Hubble’s Exciting Universe: Measuring the Universe’s Expansion Rate (Hubblesite)
Planck (ESA)
WMAP- Content of the Universe (NASA)
Supernovae Were Discovered in all These Galaxies (Universe Today)
What are Cepheid Variables? (Universe Today)
Carnegie Supernova Project II: The Slowest Rising Type Ia Supernova LSQ14fmg and Clues to the Origin of Super-Chandrasekhar/03fg-like Events (The Astrophysical Journal)
Research team discovers unique supernova explosion (Phys.org)
Planck and the cosmic microwave background (ESA)
Hydrogen Epoch of Reionization Array (HERA)
FOLLOW-UP: What is the ‘zero-point energy’ (or ‘vacuum energy’) in quantum physics? Is it really possible that we could harness this energy? (Scientific American)
First principle (Wikipedia)
WMAP Inflation Theory (NASA)
Could a Dark Energy Phase Change Relieve the Hubble Tension? (Universe Today)
Michael S. Turner (University of Chicago)
What is the Casimir effect? (Scientific American)
The Nobel Prize
The Higgs boson (CERN)
Particle Fever (2013) (IMdB)
Back to Top
TranscriptTranscriptions provided by GMR Transcription Services
Fraser Cain: Astronomy Cast Episode 669, Challenges to Dark Energy. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I’m Fraser Cain, the publisher of Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmo Quest. Hey, Pamela, how you doing?
Dr. Pamela Gay: I am doing well. The third episode of our new TV show aired Saturday and we got it to the station 90 minutes before it was due, due to computer crashes, because computers know.
Fraser Cain: Yeah.
Dr. Pamela Gay: But if you haven’t checked it out yet, it’s Escape Velocity Space News. It airs on Now Media and I am gonna be putting together a podcast version and loading that up later today.
Fraser Cain: Congratulations, that’s amazing. It’s been over 20 years since astronomers first discovered that the expansion of the universe is accelerating thanks to dark energy. And in these decades, astronomers still don’t have much evidence for what could be causing the increased expansion rate. Maybe there’s something else going on to explain it.
If you go back into the archive of Astronomy Cast shows, one of the first episodes that we did was Dark Matter and then after that was Dark Energy, like within the teens anyway and we’ve brought it up a couple of times since them, but I had been expecting in the 15 years that we’ve been doing this show that we would have something more to say on the matter. But to be honest, not much has been figured out, apart from some really interesting new surveys, like the Dark Energy Survey Telescope, the development and eventual launch of the Nancy Grace Roman Telescope. We still have no idea what this is.
Dr. Pamela Gay: One of the things that actually caught me by surprise is I was expecting to spend today talking about the new results from the Dark Energy Survey and the South Pole Telescope, and there are actually two really cool papers that have both come out in Phys Rev Letters in the past couple of months that are both clearly the, hi, we’re theorists, we have predictions, there are only two of us on this paper, please give us the Nobel Prize when our predictions prove true.
Fraser Cain: Right.
Dr. Pamela Gay: And so, we may be getting to the point that theorists are starting to figure out how to get a handle on things, and they’re finding answers that may also help confine dark matter, which is kinda cool.
Fraser Cain: Well, that’s great. So, then, I guess, what is the evidence for dark energy?
Dr. Pamela Gay: Basically it comes down to when you measure the distance to a supernova and you measure the rate at which that galaxy is moving away from us using doppler shifts. We find that the universe is actually accelerating over time, which is not something that was in anyone’s predictions but it was in the math in the form of a constant to the equations of state for the universe. When Einstein originally came up with these equations there was an integration factor, when you integrate you have to add a constant, and he assumed that the constant would have a value that caused the universe to be static.
A few years later, Hubble came along, found the universe is expanding. Now we have a constant that makes sense for that. But it turns out that if you have a universe that is accelerating apart, that is a value for the equations of state, and so now what we’re finding is, in order to explain the geometry of our universe, which is flat, flat, flat, very flat, and an accelerating universe, you have to have 70% of the universe made of something that isn’t observable matter, that’s about 4-1/2 percent of the universe, that isn’t dark matter that gets observed through gravitational lensing, gets observed through rotation curves of galaxies, gets observed through the motions of galaxies and clusters, that’s 27-ish percent and instead you have dark energy.
Fraser Cain: So, this measurement really relies on how good the measurements to those type 1A supernovae are.
Dr. Pamela Gay: Yes. And it also comes down to, once we realized, okay, so we have from the Planck Observatory the flat geometry and then you combine it with everything else and you look at the mass density of the universe, the only way to explain the mass density of the universe is to have this extra stuff as well. So, you can get to dark energy from a couple of different ways but to get at the value that we’re seeing, yes, that came very clearly from the 1998 observations that the universe is accelerating with time and its expansion.
Fraser Cain: And we did some coverage on a new database that came out a couple of months ago, where astronomers had gone through and like recalibrated, normalized all the data for about 1,000 total type 1A supernova measurements and if anything, have gotten even more accurate.
Dr. Pamela Gay: Yeah.
Fraser Cain: You overlap the Cepheid variables with type 1A supernovae, the distance ladder is beautiful, the error bars are ever shrinking and the amount of dark energy in the universe is zeroing in on this. They’re really nailing this number.
Dr. Pamela Gay: And one of the wild things about this is we keep trying to find an excuse that maybe further back in the universe these kinds of supernovas, due to the change in the chemistry, would have different properties, and we do keep observationally finding random exceptions. There was a super cool type 1A supernova that went off while inside of another star, which is one way to blow up a white dwarf.
Fraser Cain: You can imagine that would pollute the results a little bit.
Dr. Pamela Gay: Right. But these one-offs that we’re finding are super cool but they are one-offs. The vast majority of the type 1A supernovae are just boring white dwarfs that ate more than they could hold without changing states.
Fraser Cain: Right. And so I guess one possibility is that the type 1A supernovae aren’t the standard candles that astronomers had always believed but the evidence is continuing to build that yes, indeed, they are.
Dr. Pamela Gay: Yeah.
Fraser Cain: Except for these ones where one star blows up from inside another star.
Dr. Pamela Gay: Yeah.
Fraser Cain: Right.
Dr. Pamela Gay: And so, I mean it’s just like saying most human adults are between five foot and six foot, yes, there are people who are only three foot and there are people who are only seven foot, but the vast majority of us are between five and six foot. So, yeah, it’s averages.
Fraser Cain: So, then, let’s talk about some of the largescale surveys that have been developed to try to get to the heart of dark energy. Not necessarily explain it, I guess, but at least to confirm it, map it, try and nail down its parameters.
Dr. Pamela Gay: So, the big one with the obvious name is the Dark Energy Survey, which was done from down in Chile where they observed with extreme sensitivity vast swaths of the sky with the goal of looking to see how the structure of the universe evolved with time. So, the idea here is, we know that the universe started out as pretty much smooth distribution of particles. It wasn’t even anything more fancy than particles initially, with slight over and under densities that were created by soundwaves moving through the early universe.
That mostly smooth distribution that we can measure in the cosmic microwave background, then had to collapse down into galaxies, stars at the smallest scales, but then clusters of galaxies, walls of galaxies, super clusters at the largest scale and it does that over time. And we have models that basically say okay, here is the CMB, here is the modern universe, let’s fill in in between and the Dark Energy Survey was designed to get at the more recent few billion years.
The next survey that is super exciting to look at is HERA, which is being done in the radio, looking at the redshifted 20-centimeter line of cold hydrogen, that the detectors for this, they’re looking at wavelengths of light that instead of being just 20 centimeters are instead many, many feet, so, longer than us. And in these longer wavelengths we are able to start seeing how cold hydrogen was distributed in the early universe, start piecing together how cold gas clumped and then got re-ionized in the era of re-ionization.
And between these different surveys, we’re working our way through measuring what was the structure over time so that we can better confine our models and say, okay, was the amount of dark energy constant over time. Was there some sort of a phase transition? Was there a kick somewhere? And these are the kinds of questions that folks are trying to answer, is what observables can dark energy give us that will help us confine our theories?
Fraser Cain: And so, in addition to the type 1A supernovae measurements, they’re able to now look at these galaxy clusters and then on top of that they’re looking at the concentrations of these regions of hydrogen gas. And so, you’ve got like three independent lines of observation that theoretically should allow you to map out the amount of dark energy.
Dr. Pamela Gay: Yes.
Fraser Cain: And is the assumption that they’re gonna find it? Like I know the Dark Energy Survey is still partway through its survey. You didn’t even mention the Nancy Grace Roman, it’s gonna be launching in 2025, and –.
Dr. Pamela Gay: Well, you don’t count your satellites until they’re orbiting.
Fraser Cain: Fine, fine, okay. Pamela, put your hands over your ears. Audience, the Nancy Grace Roman, one of its main jobs is going to be to characterize dark energy, doing kinda the same thing that the Dark Energy Survey is but from space. So, this is classic, right. Like if you don’t have an easy answer then you build more instruments, more observatories. You keep trying to characterize the nature of the problem, building hypotheses, testing them against your observations, removing bad ideas one after the other and hopefully trying to pin down the final thing. So, we may never know what’s causing dark energy but we’ll have it measured to Six Sigma accuracy.
Dr. Pamela Gay: Well, and the other side of it is the particle physics side. So, we know that dark energy, whether it’s a force, an energy, a field theory, whatever it is, puts into every cubic meter of space basically a proton-ish worth of energy. And so, how do you explain that energy existing? And by better understanding the quantum mechanic side of the universe, the particle physics, the vacuum energy, are sterile neutrinosactually a thing or not, this is another way of coming at the fullness of the universe by looking at the smallest factors inside of it.
Fraser Cain: All right. So, I guess, you found a few papers that have been proposing some alternative explanations that would explain the observations but not necessarily be new energy that’s being injected into every cubic meter of the universe, which I guess sounds satisfying. Like the fact that energy is appearing out of nowhere, that’s unnerving, so what are they proposing?
Dr. Pamela Gay: So, the first paper in here, I have to look at my notes, the first paper came out from Martin Sloth and Florian Niedermann, where they’re looking at new early dark energy. And the idea here is our universe has undergone phased transitions in terms of the energy of the entire universe. So, the first massive phased change occurred in the first fractions of a second, where we essentially went from every basically molecule sized bit of the universe expanding out via inflation, which we also don’t know what is, to be about the size of the observable universe according to some ways of looking at it.
And this massive, fairly instantaneous epic of inflation may have only been one of two phased transitions or there could have been a later phased transition that, if there testable ideas are right, leads through first principles to having a cosmological constant of 72, which is within error bars of what we see for the modern universe, and fixes the discrepancy we see with the old universe.
Fraser Cain: And so, sorry, so like, the idea of inflation –.
Dr. Pamela Gay: Yes.
Fraser Cain: Happening in just the first fraction of the Big Bang was developed I think back in the ’70s –.
Dr. Pamela Gay: Yeah.
Fraser Cain: To help explain a lot of the problems with the Big Bang. Like the Big Bang beautifully explains the universe as we see it today, but there are these flaws in the theory. How can vastly separated parts of the universe be similar temperature, there’s a bunch of these ideas. And so, one of the theories is that, in fact, there was this period of rapid inflation that carried everything away from each other really quickly and then it settled down.
So, I think baked into modern cosmology is already this idea, as you say a phased changed, a dramatic change in the expansion rate of the universe. So, it doesn’t seem that surprising that there could then have been others later on.
Dr. Pamela Gay: Right.
Fraser Cain: So, when would have this other, they’re calling it, what, early, what are they calling it, early –?
Dr. Pamela Gay: They’re calling it new, early dark energy.
Fraser Cain: Dark energy. Right, okay.
Dr. Pamela Gay: So, NEDE is the abbreviation.
Fraser Cain: New early dark energy, right. And so when would this have occurred in the timeline of the universe?
Dr. Pamela Gay: This still would have occurred during what they refer to as the dark times prior to the release of the cosmic microwave background. And it fits in with the way – Michael Turner, who is a prominent cosmologist, now professor emeritus from the University of Chicago, he says there’s basically these three unknown pillars of cosmology, inflation, dark energy which he actually named, dark matter. And so, this looks at that early period, makes some solid predictions for temperature details that we should be able to see with enhanced continuing to look at the cosmic microwave background, which tells us everything apparently.
But it also makes some finite predictions for what kinds of neutrinos should be out there, and what kinds of specific particles we can expect to find, thus, also perhaps explaining dark matter. So, we have one coherent theory spelled out in a letter-sized research article making concrete predictions. It seems good and just needs tested now but it’s not the only one out there.
Fraser Cain: All right. Well, let’s talk about the other one, then.
Dr. Pamela Gay: So, the other one is by Alexander, and I’m going to mispronounce this and I am sorry, this appears to be a Ukrainian last name, Tkatchenko, and the other one is Dmitry Federov. And they look at the vacuum energy of the universe, and vacuum energy is something we know is real because of the Casimir effect, which is just one of the best named effects in particle physics. The dude’s name was Casimir but it just sounds cool to say.
And what the Casimir effect says is if you take two plates that are capable of conducting electrons and you put them extremely close together but you’re not actually running charge through them and they’re not being exposed to any fields, nothing should happen I a vacuum. But the reality is, if you put these two plates just a couple nanometers apart within a vacuum, they will either attract or repel due to the constant creation and destruction of virtual particles that are in their creation and destruction, creating a field. So, if you have a proton spring into existence as a virtual particle between these two plates, that proton has a field and it creates the effect.
Fraser Cain: Right.
Dr. Pamela Gay: And we see this.
Fraser Cain: Right. And if I understand, like the Casimir effect, because the gap is so small the virtual particles of only certain sizes can pop into existence outside or as a field.
Dr. Pamela Gay: Right.
Fraser Cain: Outside the plates and then they are pushing inward, there is essentially a field on the outside and not so much field on the inside and it’s pushing on these plates. And once you move the plates farther and farther apart, now there’s room for the fields to appear both in between the plates and outside the plates.
Dr. Pamela Gay: Yeah.
Fraser Cain: And then that force goes away. And it sort of shows you the presence of this vacuum energy that is everywhere. And it’s been beautifully measured, so no one argues with the existence of vacuum energy. The assumption, though, is that this energy cancels out, goes away very quickly and doesn’t provide any ongoing force to the universe.
Dr. Pamela Gay: And that’s one school of thought. Another school of thought is, no, it’s totally providing dark energy-like forces, but when they do all the maths, they have consistently come up with an amount that is too large by a factor of 10 to the 120 for the theories that I like the best and that are among the prominent theories. And the best case for getting it down has, until this paper as far as I know, been 10 to the 30th. And when you’re off by somewhere between 10 to the 30 and 10 to the 120, it really doesn’t matter.
Fraser Cain: That’s a lot. Yeah.
Dr. Pamela Gay: It’s a lot. And this is where these two researchers, Tkatchenko and Fedorov, they said, well, okay, what if the vacuum energy has a polarizability, that the particles can actually have alignments that affect what can and can’t come into existence and annihilate. And they make again solid predictions that should be testable if we go looking with new technology that we don’t currently have laying around.
And it’s just one of those nice, simple, elegant ideas of we know stuff can be polarized. We know particles can be aligned. What if just the universe as a whole has this polarizability characteristic to it that we just hadn’t been including? And again, with this research, it makes set predictions on what to go look for. It looks at the particles that are out there and says, okay, here is what to see in particular physics and I don’t know which team I’m rooting for more. I like the polarizability one.
Fraser Cain: Why choose?
Dr. Pamela Gay: Well, I mean that’s – it’s two theory papers making predictions. Both of them have only two authors. Both papers are clearly gearing up for a Nobel Prize. It’s always good to cheer for people but I guess I’ll cheer for both.
Fraser Cain: Yeah. When you think about the winning Nobel Prizes, many of them start this way.
Dr. Pamela Gay: Yes.
Fraser Cain: That a theorist puts together a paper and says there should be a particle called the Higgs boson, right, and then 30 years later experimenters are finally able to find it, and this is the same thing. So, I mean I guess if dark energy makes you uncomfortable already –.
Dr. Pamela Gay: This doesn’t help.
Fraser Cain: Buckle up. Yeah.
Dr. Pamela Gay: Yeah.
Fraser Cain: You still got another 30 to 50 years of searching and scanning and trying theories to try and narrow in on an answer to it.
Dr. Pamela Gay: And if you want to get a feel for what it’s like within the field of particle physics to watch people so clearly chasing Nobel Prizes, watch the moving Particle Fever, it is very delightful. It shows the good, the bad and the ugly of scientists being scientists, and just the joy that comes from people getting to see their dreams come true through instrumentation.
Fraser Cain: I will check that out.
Dr. Pamela Gay: It’s really cool.
Fraser Cain: Yeah, that’s awesome. All right. Well, thanks, Pamela. I hope within the lifetime of Astronomy Cast we will do the show we finally know what dark energy is. After we do the show where we say we finally know what dark matter is, we will do both those shows. This is my promise to all of you.
Dr. Pamela Gay: And this is where it’s just sort of like we can hope, and when that finally happens is that when we retire?
Fraser Cain: No, no.
Dr. Pamela Gay: Okay.
Fraser Cain: Because there will be there will be a hundred new mysteries that are even –.
Dr. Pamela Gay: We keep going until we die.
Fraser Cain: Yeah, there will be a hundred new mysteries that are even more complicated and more troubling, so, no, that’s how this whole process works. All right, Pamela, thanks a lot.
Dr. Pamela Gay: Thank you. And thank you to all the patrons out there. I don’t actually have a thing of names, I just discovered, to pull out because it’s the very beginning of the month and the list hasn’t been generated yet but I do want to say thank you to all of you. We have been reading the names of just a subset of you on air, it’s one of the perks associated with the different levels but we love all of you, whether you’re a $1.00 a month contributor or a $100.00 a month contributor. You allow us, through our ongoing efforts, year after year to allow us to pay our humans and keep the show going, and occasionally replace cables from my camera when they die. So, thank you.
Fraser Cain: I will take this opportunity then to sort of mention a trend, a disturbing trend that you who are a fan of educational content should be aware of and that is artificial intelligence generated content.
Dr. Pamela Gay: Yeah.
Fraser Cain: That more and more websites are moving to this model of getting ChatGPT and other artificial intelligence to generate en masse the material and this trend is going to accelerate.
Dr. Pamela Gay: Yeah.
Fraser Cain: And it’s just another career that is gonna be –.
Dr. Pamela Gay: Go away.
Fraser Cain: Go away, sunsetted. The career of the science communicator and that’s because it’s way cheaper to let a large language model generate explainer content. And hopefully, Pamela and I have value and place in this society as more and more of this content shifts into being generated by enormous databases. I know it sounds shocking and surprising but this is where it’s all gonna go and it’s gonna happen startlingly fast. So.
Dr. Pamela Gay: We have had people write in and say, hey, why don’t you switch over to using ChatGPT to generate your scripts.
Fraser Cain: Right.
Dr. Pamela Gay: It’s already people are suggesting it.
Fraser Cain: Yeah, yeah.
Dr. Pamela Gay: And we won’t do that.
Fraser Cain: Yeah. I will get ChatGPT to recommend ideas but I won’t –. See, here’s the key, there are no scripts, that’s the trick.
Dr. Pamela Gay: Right, right.
Fraser Cain: So, how could we have a script if there are no scripts? Smart. Anyway. So, if the work that we’re doing, like if the loss of science communicators at the mainstream media was already troubling to you, now they’re coming for all science communicators. So, if supporting the work that we do is important to you to make sure that we can keep doing the show, paying the people on the team, keeping the servers running, all of that, join our Patreon.
Dr. Pamela Gay: Thank you.
Fraser Cain: Patreon.com/astronomycast. Thanks, everyone, and we’ll see you next week.
Dr. Pamela Gay: Bye-bye.
Back to Top
Astronomers have made extremely accurate measurements of the expansion rate of the Universe and come up with different results. And the error bars for the observations don’t overlap, so there’s something strange going on. What’s the answer and how can the Crisis in Cosmology be resolved?
Download MP3 | Show Notes | Transcript
Show NotesSee Comet ZTF (C/2022 E3) Dash Between Big and Little Dippers (Sky & Telescope)
Comet Hale-Bopp (NASA JPL)
Comet Hyakutake (NASA JPL)
Comet NEOWISE, the best comet of 2020 (EarthSky)
Comet McNaught over the Pacific Ocean (ESO)
Hubble Tension Headache: Clashing Measurements Make the Universe’s Expansion a Lingering Mystery (Scientific American)
Hubble telescope refines universe expansion rate mystery (Space.com)
Megaparsec (Swinburne University)
Messier 87 (NASA)
Andromeda galaxy: All you need to know (EarthSky)
Ask Ethan: Is there a better way to measure cosmic time? (BigThink)
Type Ia Supernova (Swinburne University)
How do astronomers measure the brightness of something? (Astrobites)
Luminosity (Swinburne University)
Standard Candle (Swinburne University)
What are Cepheid Variables? (Universe Today)
Gravitational Lensing (Hubblesite)
Dr. Adam Riess (Space Telescope Science Institute)
Astronomical deep-sky photometry and spectroscopy (BBC Sky at Night)
Gaia (ESA)
Baryon Acoustic Oscillations (NASA)
COBE (NASA)
Planck (ESA)
LAMBDA – ΛCDM Model of Cosmology (NASA)
Astronomers Grapple with JWST’s Discovery of Early Galaxies (Scientific American)
How Did Inflation Happen — and Why Do We Care? (Space.com)
The Big Bang (NASA)
IMPROVING MEASUREMENTS OF THE COSMIC EXPANSION WITH GRAVITATIONAL WAVES (LIGO)
Cosmic Inflation Theory Faces Challenges (Scientific American)
Sloan Digital Sky Survey
The Dark Energy Survey
JWST (NASA)
Back to Top
TranscriptTranscriptions provided by GMR Transcription Services
Fraser Cain: AstronomyCast, Episode 668, “The Crisis in Cosmology.” Welcome to AstronomyCast, your weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela, how you doing?
Dr. Pamela Gay: I am doing well. How are you doing?
Fraser Cain: Doing great. Yeah, nothing to report.
Dr. Pamela Gay: That, I think, in 2023, is really the best any of us could ever ask for.
Fraser Cain: Yeah, the weather is fine, the snow is gone, I’m getting out and doing a bunch of hikes and stuff in the nature, even though it’s wintertime, but still, garden’s coming along.
Dr. Pamela Gay: Dang.
Fraser Cain: I saw the comet last night. It sucks, but…
Dr. Pamela Gay: Oh well.
Fraser Cain: Yeah, it’s gotten quite diffuse at this point, so although it’s bigger and brighter, it’s also more of just a cloud.
Dr. Pamela Gay: It’s spread out, so the light from any given place – its surface brightness is really low.
Fraser Cain: That’s right, so you really don’t get that nice, little, tight nucleus with the tail, you just get this – what looks like a little cloud in the sky. But still, it’s easy to find. It’s so easy to find because it was right beside Ursa Minor, right beside the Little Dipper, and then, it’s moving towards Cassiopeia. So, if you have never seen a comet – you can’t see it with your eyes, but you can see it in a pair of binoculars or a small telescope. It’s easy to find, and that’s nice, as opposed to one where it’s in a fairly difficult constellation to discover. But unfortunately, completely inaccessible now to the folks in the Southern Hemisphere, so this one is just for the folks in the north. So, if you haven’t already –
Dr. Pamela Gay: Who do not have cloud like the Midwestern folks in the north.
Fraser Cain: Right, yeah. It’s gonna peak in just a couple of days from now, so now is your chance, and then it’s just gonna get – but it mostly sucks. I always compare comets to Hale-Bopp and Hyakutake, and people are even like, “Oh, didn’t you like Comet NEOWISE?” I’m like, no.
Dr. Pamela Gay: No.
Fraser Cain: No, it sucked. I could see it with my eyes. That does not a good comet… That is necessary – sufficient but not necessary? Anyway, just barely being able to see a comet with the unaided eye does not – you do not declare victory in the comet world. No, you want the one that is gigantic –
Dr. Pamela Gay: The tail.
Fraser Cain: The tail spans multiple handspans across the sky, that you can see it even in light-polluted skies. That’s a comet, and everything else the universe is sending our way right now is mediocre, and I reject them. So, no, NEOWISE sucked, McNaught sucked, this one sucks. We demand better. I will wait, but I’ve been patient for too long. Come on, comet!
Dr. Pamela Gay: I…I can’t argue with that. All of that is true. It’s all true.
Fraser Cain: Yeah. For people who are like, “Oh yeah, Comet NEOWISE was fine,” no, it wasn’t! It wasn’t, and you’re settling. You deserve better. I deserve better. We deserve better comets. The universe can provide it; it’s done it in the past. It’s time to put up or shut up. All right.
Dr. Pamela Gay: Yeah…
Fraser Cain: Astronomers have made extremely accurate measurements of the expansion rate of the universe and come up with different results, and the error bars of the observations don’t overlap, so there’s something strange going on. What’s the answer, and how can the crisis in cosmology be resolved? So, what is the crisis in cosmology?
Dr. Pamela Gay: So, some people call it the Crisis, some people call it the Hubble Tension. A lot of us just put “WTF?” and call it a day. So, what’s happening is before the supernova teams did such an amazing job of measuring the present expansion rate of the universe, we were like, “Nah, the universe is expanding somewhere between 50 kilometers per second per megaparsec to 100 kilometers per second per megaparsec,” and I had so many profs that were like, “Just use 100. It makes the numbers easier.” It was pleasing.
Fraser Cain: Right. Just so people understand this idea, that you take a megaparsec of space, which is about 33 million lightyears of space, and when you think about that, that is the distance between us and faraway galaxies, like Andromeda’s really close. We’re talking about galaxies that are 30 million lightyears away, like M87 is kind of in that – when you think about the supernova image. Every second that goes by, those objects are now 100 kilometers farther apart, or 50 kilometers farther apart.
Dr. Pamela Gay: And it is a function of how far something is away from you, so the further something is away, the faster it appears to be moving away from you. A lot of people use a raisin bread analogy on this because the raisins stay the same size as the bread dough expands, so two raisins that start really close together will end up a little further apart, two raisins that are really far apart initially will end up seriously far apart by the time that bread is done rising.
Fraser Cain: And why is knowing the expansion rate of the universe important?
Dr. Pamela Gay: It’s one of those things that allows us to put together all the rest of our cosmological ideas of how you go from our universe being a single point to expanding out, to forming hydrogen and helium, trace amounts of lithium and beryllium, to – the whole story is tied up, and it slowed down or it sped up, and understanding what rate we’re going now, since there’s no accelerator pedal that we know about, what we see has to be defined by the physics of our universe, and we can start to define all that physics of the universe if we know this one number that refuses to be measured.
Fraser Cain: I apologize, I was off by a factor of 10 there, so, sorry, and you should have caught me – it’s surprising you didn’t – but a megaparsec is 3.3 million lightyears, not 33, so Andromeda, roughly, is in that ballpark range. So, apologies.
Dr. Pamela Gay: Yes. The way I think about it is someone in Andromeda looking back at us would be seeing Neanderthals.
Fraser Cain: Right, but astronomers don’t think in lightyears, they think in megaparsecs, so if I get off by a factor of 10, that’s fine by you because you don’t even think about it, so apologies in –
Dr. Pamela Gay: It’s true.
Fraser Cain: Yeah, the general public thinks in lightyears while astronomers only think in parsecs and megaparsecs, but yeah, so, apologize, let’s continue. So, why – you were discussing why knowing the expansion rate of the universe is important.
Dr. Pamela Gay: It basically just gives us this reference point that we can work all the other maths back from.
Fraser Cain: So, how long the universe has been around for?
Dr. Pamela Gay: How long the universe has been around for, basically –
Fraser Cain: What will happen in the future…?
Dr. Pamela Gay: The one that gets me is by understanding the current expansion rate, we can actually figure how fast the universe went from being a mostly smooth distribution of gases to forming galaxies, to forming galaxy clusters. The rate at which we formed large-scale structure, at a certain level, hinges on how fast our universe is expanding. It’s everything.
Fraser Cain: Right. And so, in the olden days, we used to get “How old is the universe?” and people would say, “Well, it’s kind of somewhere between 10 and 20 billion years old,” and that’s that range of measurement. If you get 50 kilometers per second per megaparsec, you get one age of the universe because you just measure how long the universe is expanding, but if you get 100, you get a different one, and they are very different, and knowing that is important. So, how do astronomers measure the expansion rate of the universe at the close and at the far?
Dr. Pamela Gay: So, there are two totally different suites of mechanisms. The “local time” way of doing it is we look for supernovae, which give off a set amount of light if they’re Type 1A supernovae – explode a white dwarf star, and you get essentially the same explosion over and over and over again, with errors that we’ve discussed in other episodes.
Measure how bright that explosion appears, measure how fast the galaxy the supernova is in is moving, and this tells you the distance using measured brightness and known luminosity, and it tells you the expansion rate by looking at the Doppler shifting. So, we’re literally measuring how much the colors of the different bands of atomic lines have been shifted by the galaxy’s motion, and that gets us a velocity.
Fraser Cain: Right. And so, we have all of these standard candles, from the Cepheid variables, to the supernova, to – I saw a list. There must have been 30 potential standard candles overlapping, going from – some of which are very well known, others of which are poorly known, but you go from local measurements using parallax that overlaps with Cepheid variables that overlaps with Type 1A supernova, and you just get this really beautiful, smooth measurement, and what number did we get from the local methods of measuring the expansion rate of the universe?
Dr. Pamela Gay: So, we’re getting around 70 kilometers per second per megaparsec, and this is using not just supernovae, but as you point out, there’s a bunch of other methods. So, folks are looking at red giants, they’re looking at planetary nebulae, they are looking even at the distant gravitationally lensed galaxies that we’re able to see multiple versions of using crazy geometry when we can see the galaxies’ lenses do the same thing at different times. All these methods are giving us definitely over 70, and narrowing in on 74, so it seems pretty constant.
Fraser Cain: Right, and the error bars are really tightening up. The quality of the observations is exquisite. I talk to a lot of astronomers, and they talk about how good of a job they’ve done with those observations, and they just gush.
Dr. Pamela Gay: The SHOES survey by Adam Reiss – they’re quoting an error of 1.3%, and they are basically going from the nearby Cepheids that they have taken some of the most precise photometry of that anyone has ever taken, then using Gaia parallax data, and then working all the way out. How often does anything in astronomy get done with that level of accuracy? We know this. The local value is basically 74 kilometers per second per megaparsec.
Fraser Cain: Right. And so, let’s go the other end of the range because there is another group of measurements that are taken not locally.
Dr. Pamela Gay: Right, and this is where things are squirrely. In the cosmic microwave background, we see these baryonic oscillations, these soundwaves that move through the early universe, causing slight over- and underdensities, and we can map so beautifully this distribution with our theoretical models, and by combining our understanding of, okay, the universe had this much regular matter, this much dark matter, this much – putting all of these base understandings that we come at from the theory, combining our average temperature information that we got from COBE and other missions, putting it all together, it gets us in the 60s, 68, generally.
Fraser Cain: But the most accurate version of this was the Planck satellite from the European Space Agency.
Dr. Pamela Gay: Right, and this is where it’s important to note the Planck data was used to get at that distribution of baryonic oscillations, and that was used in combination with a mean temperature that they were, in a lot of the papers, referring back to COBE data. So, Planck got us, very specifically, deviations about the mean, and we just fed all the data together in the context of what’s called lambda cold dark matter.
This is a theoretical framework that says that our universe is not just expanding, but it’s accelerating as it expands, that the dark matter, the stuff that we’re not really sure what it is, that may be related to neutrinos in some way – whatever it is, it wasn’t moving extremely fast early in the universe, so that’s where the “cold” part comes in. So, we have lambda, the dark energy, and cold dark matter, two things we have very poor understanding of. When you combine those with the data, it gets you, again, roughly 60 kilometers per second per megaparsec with error bars that don’t overlap.
Fraser Cain: Right, and this is the key. So, you look at the local neighborhood and you get a measurement that’s in the low 70s with very tight error bars, you look at the early universe, you get 68 with very tight error bars. Both are exquisite observations, both are trying to tell you the same thing, and they disagree with one another, and this, at the heart, is the crisis in cosmology.
Dr. Pamela Gay: Correct.
Fraser Cain: So, this is the crisis in cosmology, so what’s the answer?
Dr. Pamela Gay: Well, this is where I personally am a bit excited, and I don’t know how many people are with me on this one because I wasn’t at the meeting, but at the American Astronomical Society meeting, there was a lot of discussion about how JWST images of gravitationally lensed early galaxies appear to be showing from two different studies that have both made it through peer review that there were already well-formed galaxies 350 million years after the Big Bang, and that’s early.
There is other work that is being done that is still going through peer review that is showing there may have already been galaxies – massive ones – at 200 million years after the Big Bang. So, with galaxies forming this early in the history of the universe, it tells us that that model we have, lambda cold dark matter, is off somewhere because while we thought there would be a couple, a few massive galaxies early on, those baryonic oscillations didn’t lead us to believe there would be as many as we are now finding.
And so, we have to figure out a new way to get from mostly smooth universe with the cosmic microwave background to galaxies forming in bigger and probably larger numbers than we anticipated to our present structure, and folks are putting out ideas like maybe there was a bit of leftover inflation, maybe the value of dark energy hasn’t been constant, and all of these different ideas – I don’t think we can really throw anything out yet, and I am the first person to want to throw out ideas.
Fraser Cain: Right. So, the challenge here is that you’ve got – the most obvious possibility is that one or both measurements is incorrect –
Dr. Pamela Gay: Yes.
Fraser Cain: – which is what would be everybody’s first instinct, that someone’s wrong, that one of these measurements is incorrect. But, because of this dichotomy, both measurements have been scrutinized and scrutinized, and teams have gone back, and all they’re doing is narrowing the error bars. They’re not finding a large discrepancy. So, that’s the one that is most likely, and yet, that seems to be less and less of the case, and so, you’re left with the universe –
Dr. Pamela Gay: New physics.
Fraser Cain: New physics, right, that our understanding of Einstein, our understanding of what those acoustic oscillations should be in the cosmic microwave background, is wrong.
Dr. Pamela Gay: And this is where I’m not gonna lay blame on anybody. Relativity seems to work so far, it doesn’t seem to be the problem, but our understanding of the distribution of kinds of matter, the way different forces interplayed, whatever the heck inflation might be – we have no idea what inflation might be – it is somewhere in this physics of how we get from the Big Bang to now that we are missing something, and it’s kind of awesome.
We don’t get a whole lot of surprises anymore, it feels like, some days. We’ve found all the particles in a standard model. We didn’t find any of the particles from supersymmetry. This gives us something new to chase, and the fact that even the folks using gravitational waves to measure distances – they’re still getting the same local universe numbers.
Fraser Cain: And that’s harder to get wrong.
Dr. Pamela Gay: Yeah!
Fraser Cain: I know I’ve talked to some people working in gravitational wave observatories, and I’ve had this conversation, and effectively, the more precise, the more powerful these gravitational wave observatories get, the farther they’re able to see out into the universe. You can rely on their measurements, so it’s another layer of observation, but one that’s very trustworthy, and it only goes so far. It doesn’t take you all the way up to the end of the universe, but maybe some future observation will.
So then, new physics – so, maybe we don’t understand how the early cosmic microwave background worked, maybe we don’t understand how Cepheid variables work, maybe we don’t understand all these different pieces, but there have been a few hints. Maybe Type 1A supernovae aren’t the standard candles that we thought they were.
Dr. Pamela Gay: And this is where there are so many different things that are getting us that local 73-ish that, yeah, I’m happy saying there are discrepancies from one Type 1A supernova to another in weirdo special cases. We’ve got to talk about some of those. If the white dwarf ends up inside of another star, that explosion’s gonna be a bit different, and that happens, but it really seems like there is something about how you get from there – cosmic microwave background – to here – gravitational waves, Cepheids, planetary nebulae, supernovae, all these other mechanisms. There’s something in the science that we have yet to uncover.
Fraser Cain: And then, another possibility is if the rate of expansion of the universe changed. So, perhaps there was a – the model that I’ve heard is this idea of late inflation.
Dr. Pamela Gay: Yeah, that’s the one I was looking at as well, where whatever it was that caused us to initially blow up, there’s a little bit of that left over that caused another kick, but we don’t understand what’s going on there.
Fraser Cain: Right, right. And so, if you had an expansion rate of 74 early on – or, sorry, 68 early on, and then it slowed down, you could get the one that’s today, and that’s even taking into account dark energy. I’m sure people are like, “What about dark energy?” That’s layered on top of this. That’s accounted for. And so, you would have this almost – instead of the universe smoothly applying the accelerator on the gas, it was like putting the accelerator a little harder, and then pulling the foot off the pedal a little bit, and then putting it on harder again, and who knows what kind of shenanigans it got up to in the intervening period? So, what is the way forward at this point? What is the way out of the crisis in cosmology?
Dr. Pamela Gay: We need to basically do a survey of just what was the distribution of galaxies and galaxy clusters in the early universe. We have done a beautiful job, first with the Sloan Digital Sky Survey, doing a volume around our galaxy. Then, with the Dark Energy Survey, we have pushed out even farther in some areas of the sky. With JWST, we’re going to be able to continue pushing the survey of structure size further and further out, watching how the universe goes from being Swiss cheese with giant holes in it to being Swiss cheese with smaller and smaller holes in it –
Fraser Cain: Right.
Dr. Pamela Gay: – and by measuring how that large-scale structure changes over time, that will start to put a different form of constraint on our models. We need to be out there, counting early galaxies.
Fraser Cain: Right, and so, you’ve got this structure of the cosmic microwave background radiation, and the hot spots and cold spots should map to equivalent clusters and distributions of galaxies, and so, you’ll know that this transition from the farthest that you can see to more recent is smooth –
Dr. Pamela Gay: Yes.
Fraser Cain: – and then, that will tell you, and you can keep moving forward at that point, but that’s a much harder observation. Weird as it sounds, the galaxies are much dimmer and harder to spot and map out than the cosmic microwave background radiation, which is everywhere in all directions.
Dr. Pamela Gay: Yeah. More telescopes.
Fraser Cain: Yeah. And then, the other side of that is going farther with gravitational waves, and hopefully, you’ll get to this point where the two overlap, where the gravitational waves reach the cosmic microwave background, or shortly after.
Dr. Pamela Gay: That is technology that someone maybe someday will fund, and we’re at that frustrating point where the next big discovery beyond what we can do with the new, massive radio telescopes that have started to catch star formation at earlier periods, and what we can do with JWST – it’s gonna take multiple nations getting together to build these 30-, 80-, however-many-meter telescopes that are being discussed to be able to look back.
Fraser Cain: All right, place your bets. It’s the close observations are wrong, the CMB observations are wrong, or there’s new physics.
Dr. Pamela Gay: New physics.
Fraser Cain: Really? That’s the most exciting outcome possibility, is new physics, so if that’s true, that would be wonderful.
Dr. Pamela Gay: Or at least a new understanding of that cold dark matter temperature.
Fraser Cain: It would be huge thing, like there was a revision to relativity that nobody saw coming.
Dr. Pamela Gay: So, again, I’m not sure saying a revision to relativity is the right way to say it because I think that what we’re looking at is something coming out of the realm of particle physics, and particle physics and relatively do not talk to one another, and I really think it’s going to be something about how particles interact in different regimes, and whatever the heck this dark energy is that’s gonna be what gets us to the solution to this discrepancy.
Fraser Cain: I think this “crisis” makes it sound like a bad thing, but you talk to astronomers, and they couldn’t be more excited. They’re so happy to not understand something, what was considered to be this bedrock idea, because the problem is bedrock is you get this ossification. Suddenly, you have this space that has opened up, where the solution is in there somewhere, and a lot of interesting ideas and theories, and a lot of brainstorming, and a lot of intellectual power gets to be put onto this problem, and they love it. They love it. So, I feel said that the term “crisis” – because you get a lot of pseudoscientists sort of rolling their eyes at scientists at this thing.
Dr. Pamela Gay: I like “the Hubble Tension.”
Fraser Cain: “Hubble Tension” – yeah, but “Crisis in Cosmology” is a better name, so I’d rather reel them in with “the Crisis in Cosmology,” and then help people understand that, in fact, astronomers couldn’t be more excited and happy to have this opportunity. All right, Pamela, thank you so much.
Dr. Pamela Gay: Thank you, Fraser, and thank you to everyone out there who makes this show possible through your patronage at Patreon.com/AstronomyCast. This week, I would like to thank Camy Raissian, Gabriel Gauffin, Benjamin Davies, Steven Coffey, john öiseth, Arcticfox, Dean, Corinne Dmitruk, Bart Flaherty, The Lonely Sand Person, John Drake, Nate Detwiler, Lew Zealand, Brian Kilby, Naila, The Air Major, Ron Thorrsen, Arthur Latz-Hall, Leigh Harborne, Jason Kardokus, Robert Hundl, Kim Barron, Paul Esposito, Ruben McCarthy, Bob Zatzke, Jordan Turner, Timelord Iroh, Daniel Donaldson, Frank Stuart, Ian Abdilla, and Geoff MacDonald. Thank you all so much for making everything we do possible.
Fraser Cain: Thanks, everyone, we’ll see you next week.
Dr. Pamela Gay: Bye-bye.
Voiceover: AstronomyCast is a joint product of Universe Today and the Planetary Science Institute. AstronomyCast is released under a Creative Commons attribution license, so love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Dr. Pamela Gay. You can get more information on today’s show topic on our website, AstronomyCast.com.
This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at Patreon.com/AstronomyCast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been AstronomyCast.
Back to Top
Knowledge moves forward, and so, we must move with it. Today we'll give you an update on some of the most fascinating, and fast-changing topics in astronomy, astrophysics and cosmology.
We think of space as a vacuum, but there are regions of different density. There are winds blowing from stars and other objects that clear out vast bubbles in space, and look absolutely fantastic in pictures. And might have been critical for Earth to even exist in the first place.
As astronomers look out across the Universe, they see various objects spewing jets of material light years into space. What causes these jets, and what impact do they have on the Universe.
Have you ever wanted to be a time traveler? Good news! You're time traveling right now. Into the future at one second per second. Too long? Don't want to wait? Good news, Einstein's got you covered. Today, let's talk about the weird world of time dilation.
The Earth's atmosphere protects us from a Universe that's trying to kill us, but it also blocks our view of the extreme cosmos, like seeing x-rays and gamma radiation. Space telescopes are changing our view of the most extreme events in the Universe.
Today, we gaze into the future of space and astronomy. What upcoming missions and events are we excited about?
It's been a while since we checked to make sure the Universe was still expanding. Yeah, apparently, that's still a thing. But in the last few years powerful new telescopes and expansive surveys have given us much more knowledge about what's happening.
This year's Nobel Prize in Physics was awarded to three brilliant researchers who worked out some of the secrets of black holes. Today we're going to talk about the chain of discoveries that led to this award.
I’ve got some bad news for you: stars die. At some point in the next few billion years or so, our Sun is going to start heating up, using up all the fuel in its core, and then eventually die, becoming a white dwarf. It will then slowly cool down to the background temperature of the universe, becoming a black dwarf.
Last week we gave you an update on the formation of elements from the Big Bang and in main sequence stars like the Sun. This week, we wrap up with a bang, talking about the death of the most massive stars and how they seed the Universe with heavier elements.
The Universe started out with hydrogen and helium and a few other elements, but all around us, there are other, more proton-rich elements. We believe these heavier elements formed in stars, but which stars? And at what points in their lives? Today we’ll update our knowledge with the latest science.
In this episode we mentioned donations. Click to learn more!
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download
Show Notes * Stellar nucleosynthesis (Wikipedia) * Stellar Nucleosynthesis: How Stars Make All of the Elements (Thought.co) * Stellar Nucleosynthesis (Astronomy Notes) * Stellar nucleosynthesis (Science Daily) * Stellar nucleosynthesis (Philosophy of Cosmology) * Nucleosynthesis (NASA’s Cosmicopia) * Nuclear fusion (Encyclopedia Britannica) * Proton–proton chain reaction (Science Learning Hub) * CNO cycle (Wikipedia) * Deuterium fusion (Hyperphysics) * Helium fusion (Hyperphysics)
Transcript
Transcriptions provided by GMR Transcription Services
Fraser: Astronomy Cast, episode 548. Stellar Nucleosynthesis, Part 1. Welcome to Astronomy Cast. A weekly facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me as always, Dr. Pamela Gay, Senior Scientist for the Planetary Science Institute and the Director of CosmoQuest. Hey, Pamela. How’re you doing?
Pamela: I’m doing well. How are you doing, Fraser?
Fraser: Good. I read that intro in an excited way to wake you up. Wake up.
Pamela: It’s the last Friday before a weeklong vacation and my body is like, tomorrow you can sleep in. Can we start now?
Fraser: I don’t – I think you need to check the calendar because, as always, Thanksgiving happened a month ago –
Pamela: We’re just always behind the ball here in the lower 48.
Fraser: Yeah, yeah. We – In Canada, we already did it. So, try to catch up. Now you – we’re actually recording two episodes today, but we will release them slowly and carefully over the next two weeks. Where are you off to? Is it just for the holiday or you got plans?
Pamela: I am doing Friendsgiving out in California. I’m gonna see our good friend David Joseph Wesley, who’s responsible for the music at the beginning of each episode. And we’re gonna go ride the Millennium Falcon at Galaxy’s Edge because that’s how you celebrate the holidays.
Fraser: That is gonna be so great. I would love to go back to Disney Land and see the new Star Wars stuff. Even though, I have a very low-key relationship with Star Wars these days. I have – I think my childhood nostalgia is now – I finally just wiped out all childhood nostalgia for Star Wars. Or maybe, the Star Wars – the over, you know, monetization and release schedule of Star Wars has finally destroyed my childhood love of Star Wars. But I would love to try all that stuff, that sounds pretty great. So, you gotta let me know how it works.
Pamela: I totally will, and you can follow along on Instagram, because I suspect there will be pictures.
Fraser: Yeah, The Expanse Season 4, though –
Pamela: Starts December 12th, which is my birthday.
Fraser: I know. I’m so excited. The universe started out with hydrogen and helium and a few other elements. But all around us, there are other, more proton rich elements. We believe these heavier elements formed in stars, but which stars and at what point in their lives? Today we’ll update our knowledge with the latest science. Pamela, the fact that there are certain amounts of hydrogen and helium with trace amounts of lithium, these are – this is one of the best indications that the Big Bang is a thing.
Pamela: It is.
Fraser: And yet – and yet, I’m sitting on a chair surrounded by a house, living on a planet and there’s not as much hydrogen, helium and trace amounts of lithium in all of these things. And so, these heavier elements had to come from somewhere.
Pamela: Exactly, exactly. And this is actually a story that usually gets simplified far more than it should. And over the past few years, different things keep coming up during our show that require us to realize that nucleosynthesis isn’t just something that happens in the cores of stars. It isn’t just something that occurs when stars explode. It’s something that occurs in all sorts of weird and awesome places that lead to, well hydrogen – sorry. That lead to helium-3 on the Moon and while two weird and esoteric elements like technetium in the atmosphere of stars. And I thought well, it was time to come back and fill in some of the gaps that we left when we tried to cram all of nucleosynthesis into one episode in the past.
Fraser: And do you remember how long ago it was that we covered nucleosynthesis? It was a long time ago.
Pamela: I want to say it was somewhere around year one or two, so – yeah.
Fraser: Yeah. Yeah, it would’ve been one of the topics that we would’ve gone after early on and there have been events and there has been new knowledge that has updated the whole process. And you think so much that it’s a two parter, so – So, let’s dig in. So, where do you want to – which parts of it do you want to cover today?
Pamela: So, I think that we start with the Big Bang and we end with the death of a non-exploding star and get all of the nucleosynthesis that occurs in those places.
Fraser: Okay. All right. So, let’s start with the Big Bang, then.
Pamela: So, initially as we’ve talked about a bunch in these episodes, our universe was just a big old ball of energy. And as that energy expanded and cooled and expanded and cooled – Less than three minutes after it’s start, our entire universe was similar in conditions to the inside of a star. Now, it wasn’t identical, we didn’t have the same kinds of reactions that happen in stars.
But, the energy, the density, they temperature of everything that was present was such that hydrogen atom cores, so protons, were able to come into existence and these protons collided with one another. We were able to get helium, we were able to get some lithium, we were able to get some beryllium. Electrons weren’t really bothered at this point because it was just a soup of hot ionized everything. But it got us somewhere.
Fraser: Now, I want to make just like one quick, sort of distinction here. So, I mean you said that it’s a ball of energy and that’s a bit of a misnomer just because it could have gone on forever. It could have been infinite in all directions, just highly dense, right?
Pamela: Right.
Fraser: Just this –
Pamela: Yes, that’s true. I – as a slip of the tongue because it was convenient –
Fraser: Yeah.
Pamela: Gave our universe shape.
Fraser: Yes.
Pamela: We don’t know if our universe has a finite to it. If it does, we’re a four-dimensional hypertoroid, which is a donut, not a ball. But we were basically a big old something.
Fraser: Right, right. Something, that could’ve been finite, could’ve gone on forever. And when we think about a star, right? We imagine the gravity is pulling in on the star, the light pressure is pushing out on the star and that balance creates the shape of the star. And yet, at the very core of the star, you’ve got the place where the magic happens, where the fusion is going on. And it is because these atoms of hydrogen are mashed together so tightly and at high temperature, that you get this fusion.
And so, how was – you said it wasn’t exactly the same as what’s going on in a star, and I kind of imagine it like it was rushing through this phase from whatever came before when it was just like this quark-gluon plasma to expanding galaxies moving away from each other. There was this transition point and that’s when all that magic happened. How is it different?
Pamela: Well, in the early universe, you had a p-process, proton process. Build up that allowed you to get that lithium and beryllium. In the centers of stars, you don’t have this. Instead what you have is the proton-proton chain that allows you to get from one kind of hydrogen to other kinds of hydrogen and eventually up to helium. But then, it skips up to carbon.
And so, because we have different temperatures, different densities in the cores of stars, this constant splay of protons, which is what basically the entire early universe was. Well, we don’t have that in the cores of stars. So, without the rapid flux of protons onto atoms, you don’t end up building up lithium and beryllium in the same way.
Fraser: Right. And so, I mean there are multiple ways the heavier elements get built up and the environment of what’s going on defines whether protons are being mashed together and turned into helium, or as you mentioned, this other chain. So, okay. So, you’ve got this time, how long – do we know about how long this was going on for?
Pamela: All the exciting parts of our universe, from the moment of expansion that was the inflationary epic, through to Big Band nucleosynthesis. All of that was over by the end of three minutes.
Fraser: Wow.
Pamela: So – yeah. It was super brief to basically get us to everything we have today.
Fraser: And if it had lasted longer then would we see more, let’s say lithium and beryllium, in the universe? And helium?
Pamela: Yes.
Fraser: Like a different quantity, different ratios?
Pamela: Yes, the ratios that we see do help constrain what the process was and tell us that our understanding of the big bang is a realistic one. So, when we talk about the Big Bang, it includes this Big Bang nucleosynthesis.
Fraser: That’s incredible. I mean, it’s incredible that you measure the ratios of these elements in the universe and then that tells you how long the universe was behaving like a star.
Pamela: And –
Fraser: And it wasn’t long.
Pamela: And this is one of the amazing things about our universe. Is, the physics works the same, no matter how you put stuff together. And so, during the Big Bang we had high energies, we had a massive flux of protons, we were able to build up heavier elements. Now, as we look around our universe, we still see the periodic influx of protons with sufficiently high energies that we’re able to well, build these elements again.
Except here, what we’re looking at is cosmic rays and cosmic ray spallation being responsible for processes that in the past, only occurred during the Big Bang. So, we still have a negligible build up of lithium and beryllium that occurs from cosmic rays hitting other particles and building up or splitting things apart and breaking down to get us to these atoms.
Fraser: That’s really cool. And so, even though we don’t have – we can’t look at the Big Bang directly, we can watch as cosmic rays impact detectors, impact the planet and produce the same cascade of particles and you can see that exact same process happening.
Pamela: And the way we often figure out what’s going on, is we simply look around and we go, that thing. That doesn’t match expectations based on our bad prior understanding. And so, we have to upgrade our understanding to match what we see. So, in the case of nucleosynthesis, our understanding came from the fact that we looked at the Sun and we looked at geology. And we couldn’t explain how the Sun had existed for so long, given all of the energy generation mechanisms we understood. People did crazy calculations like figuring out how much total energy and how long could the Sun burn for if it was made of something that functioned like coal.
Fraser: Yeah. Right.
Pamela: And that doesn’t work. So, they –
Fraser: It was a valiant effort.
Pamela: It was a valiant effort. But the amount of energy released in such inefficient processes as burning organics, which is what you’re doing with coal, that can’t power a star for the geologic times that we were beginning to realize had existed. So, in the early 1900s, with the advent of quantum mechanics, with advances in electromagnetism, with the beginning general relativity, we also saw nuclear fusion coming out. All at once, all of these understandings just arising in a few short decades. And it changed how we look at our sun, allowing us to see that in main sequence stars, another thing that was being figured out at the same period in time.
Gravity crushed down the star and it gets supported outwards by light pressure. These are the equations of hydrostatic equilibrium. Chandrasekhar has some of the best explanations of this. And you can figure out for each combination of radius and mass, what the internal density will be, what the internal temperature will be and what nuclear reactions that allows to happen.
Fraser: Right. And so then, you know, you had mentioned sort of earlier on that there are different kinds of nuclear reactions going on in the cores of stars than the kinds that we see – that we would have seen at the beginning of the universe.
Pamela: So, we start off with the proton-proton chain and this is where we slam together two helium atoms. We’re able to get off two hydrogens and a helium-4. And that helium that we started with going into that final result that gives us the helium-4, which is stable. That started with, we paired together two hydrogens. They gave us deuterium and a regular hydrogen. And deuterium is a hydrogen with a neutron.
We then collided those together, we got helium-3. We combined those helium-3s, we got a stable element. And one of the defining characteristics of nucleosynthesis is we’re going from something that was stable and hanging around and able to get heated up and compressed through, quite often, really unstable short-lived things.
Fraser: Right.
Pamela: And then, we’re eventually building to something stable. And the helium-4 atom, that is stable. And once you have that, you’re able to start doing even more.
Fraser: It must have been – that must’ve been a real puzzle, right? That you think about, like if you sit down and try to figure out the math, the particle physics math, and you take your hydrogen atoms and you try fusing them together into more complicated things like a stable helium. You can’t get there from here. That the outcomes won’t be stable. And so, it must’ve been an incredible leap of imagination to say okay, so maybe there are a bunch of intermediate unstable forms that are being pushed together and those are then turning into the stable forms that we’re familiar with. To get from hydrogen to helium.
Pamela: And additional leaps were also needed where they had to figure out okay, why is it that these things that have proton rich cores and should be repelling each other, how is it that they can finally get close enough? How is it that we can overcome these different forces? Where are those pockets of allowed reactions where we can overcome the repulsive forces, where we can get new things into the nuclei and we can allow these processes to happen?
That particular helium-4, that is a really annoying atom to try and get past, because it is so stable. And this is where you really need to have a significant burning process already in place before you can start well, building it up into other things as well. Yeah, helium-4 wants to stay helium-4. It’s annoying that way.
Fraser: Right, right. And so, ideally it would degrade and then you would have a transition that you could then use to go to a heavier element.
Pamela: And we just don’t have this, and this is where instead what we have to start looking at is, what are the cores of stars seeded with? This is where we start looking at, is there any existing carbon around that can have nuclear reactions with hydrogen? Once you can get carbon and hydrogen going together, now you’re producing nitrogen which produces more carbon. That carbon can then produce more nitrogen and you just have this ongoing cycle of carbon, nitrogen and oxygen that’s just building and building, releasing more elements as it goes.
Fraser: And does that happen inside a star like the Sun, or does it have to be a heavier star?
Pamela: This can happen in stars like the Sun.
Fraser: Okay.
Pamela: And what’s cool is it couldn’t happen in that first generation of stars. Because there wasn’t the hydrogen – there wasn’t the carbon to seed this particular cycle.
Fraser: So, with – I mean, it’s kind of like a catalyst in another kind of reaction where you can’t have a reaction without the catalyst. And so, once you were able to get that carbon from some other – the death of other stars, then that could seed these stars and they could help with that. That’s really interesting. I like that.
Pamela: And our Sun doesn’t currently have this reaction going on, just to be clear. This is something that can happen later if its core heats up, which is possible later on. But when you have bigger stars, stars that are 1.3, 1.4 times the mass of our Sun. Their core is actually dominated by this process when they’re on the main sequence. So, when we talk about main sequence stars burning hydrogen in their core, we’re talking about the majority by number, but not the majority by type. Because there’s a whole lot of bigger stars out there.
Fraser: Right, right. And I mean, I think where this whole conversation is going is just the fact is that I mentioned earlier on, right? Which is that I’m, you know, I’m made of meat, I’m sitting on a chair, I’m in a house, the house is made of carbon, I’m breathing in atmosphere made of nitrogen, right? All of these heavier elements. So, how do they get out of the star? Because, why doesn’t the star just – there’s a lot of gravity going on and when the star dies, why doesn’t it just hang on to all of it and then we never get it?
Pamela: Well, we’re dealing with a bunch of different processes here. So, I – first of all, stars like our own Sun, they’re eventually going to run out of fuel in their core and the core is going to quietly collapse down into a white dwarf, while the outer atmosphere puffs off. And through various dredging processes, mixing processes, you can churn up material from deep in the star to the outer layers. That’s one way that you can release some of these elements. And what’s cool is we’ve talked about the nuclear fusion going on in the core somewhat.
We’ve talked about main sequence stars, we have the helium production, we have CNO production. The story that we talk about all the time is bigger and bigger stars can build bigger and bigger atoms in their core. Burning silicon, burning neon, eventually getting us all the way up to iron. And the issue is, where do other elements come from that aren’t formed in supernova and this is where the outer atmosphere of stars are actually an often-ignored production site.
Fraser: Oh, that’s really interesting. So, what’s going on there?
Pamela: So, our Sun, in the process of going through all these different activities is giving off neutrons. And when you give off a neutron, you are bombarding the outer layer of your star with neutrons. And the neutrons, when they hit the atom – when they hit the atomic cores of atoms in the outer atmosphere, they can build up there. And so, this is a matter of you collide those two hydrogens together in that proton-proton chain and one of the byproducts shooting off is that neutron. So, that neutron goes flying out, it hits the core of an atom.
Now, neutrons aren’t always stable and if you build up a whole lot of neutrons in the outer – in the atoms and in the outer part of the star, those atoms over time are going to go, too many neutrons. And they’re gonna undergo beta decay processes where those neutrons get transferred into protons, building up a heavier element. So, we’re essentially slowly building things up the periodic table. And the way we figured this out is the existence of technetium in the outer layers of stars. And any of you who are out there, who’ve ever had to do high-resolution spectroscopy of stars, you know what I’m talking about here. Because you look at –
Fraser: Technetium? Is that a real thing? That just sounds like a made-up word from Stargate or something.
Pamela: It does.
Fraser: Yeah.
Pamela: It does. It’s totally a real thing. And it’s this really annoying metal atom that has all these electron shell layers that it loves to have so many spectral lines. So, you’re going through trying to measure your elements and every third line it feels like is coming from this one annoying metal that’s unstable. And its shelf life, its half-life, is such that you wouldn’t expect to ever find it in a star because the stuff that star was formed out of, by the time you’re seeing technetium in the outer atmosphere, looking at red giants for instance, it should all be decayed away.
It should not be there. So, when you see in the outer atmosphere of a star, a short-lived atom, that atom had to form in that atmosphere. And this is how we figured out there are what are called S-process atoms, slow-process neutron capture elements like technetium that are getting built up in the outer atmospheres of stars as these neutrons fly out and get captured. So, some of the elements that we’re dealing with, not technetium, but many other things that we’re dealing with, lead for instance.
The only way to explain these peaks that we see in the ratios of atoms in the periodic table, is to see these elements as forming through S-process, in atmospheres of stars, getting released during the planetary nebula phase. Getting released in solar winds. Getting blasted out across the universe to be recycled into worlds like ours.
Fraser: Right. And so, the stuff that’s in the core, like if it doesn’t go full supernova, the stuff in the core –
Pamela: It’s staying.
Fraser: It’s staying there. And so, that’s why – like the Sun will eventually turn into a gigantic diamond, right? When it cools –
Pamela: Yes.
Fraser: When it cools down and crystalizes and you just get all these carbon atoms and lockstep with one another. And good luck chipping a chunk of that thing off and selling it. It’s locked in. And so, it’s not available to seed another star. But this – these heavier elements that are constantly being constructed in the outer atmospheres of stars and then being easily blown away because that’s where the solar wind is emanating. That’s absolutely fascinating to imagine this stream of stellar material that’s firing out into the surrounding nebula to then acts as a catalyst for future stars.
Pamela: And this is the way that we just don’t think about atoms forming. And it’s one of these things where there’s so many different ways that we end up with neutrons and there’s so many atoms that can only be explained from various parts of bismuth, to plutonium, to even more elements of lead where we’re relying on the S-process to get at the things that we see in the sky and see in our tables, chairs and selves.
Fraser: And so, really any place where you’re getting neutrons mushed together, you’re potentially getting those neutrons decaying and turning into protons of various types.
Pamela: And the catch is, this happens in two ways. There’s a slow-process, which is the one that we’ve just finished – well, we’ve just hit on, I won’t say we’ve ever finished the discussion. But there’s also rapid-process, which is where you have a blast of neutrons from an exploding star. But that, I think, is a topic for the next episode.
Fraser: That’s gonna be the next episode. So, people are gonna have to stay tuned. Was there anything else you wanted to cover for this episode?
Pamela: I think the last thing we should probably hit on is the other way that we end up with nucleosynthesis is a comic ray spallation, which we sort of touched on. And this is really cool because of how it affects lithium and beryllium. And it’s the kind of thing that when we’re looking out at the interstellar medium, we often talk about the search for super unprocessed raw interstellar materials that represents what came out of the Big Bang. But that unprocessed material, when it gets hit by cosmic rays, this cosmic ray spallation is enriching that material. And so, we actually have in the cold, dead night – cosmic rays changing these clouds. Now, to be entirely fair, this is such a minute process.
Fraser: Right.
Pamela: It doesn’t even like raise a bleep on our radar. But I think it’s cool and worth noting, so –
Fraser: And when you think about over time, over billions of years, with the enormous number of cosmic rays that are firing through the universe all the time, striking atoms. It’s not zero.
Pamela: It’s not zero. And so, when we look at these clouds that may have been enriched by like a single supernova. That enriched material, it’s getting broken down as we watch. Getting turned into these latest elements and that’s kind of awesome.
Fraser: That’s really cool. All right, well for supernovas, all the explosive events, that is next time. Thanks, Pamela. Do you have any names for us this week?
Pamela: We are here thanks to you wonderful humans who have the patience to not just be listeners, which I don’t think really requires any patience, but you actually like go to the internet and go to patreon.com and support us. Which means we can pay Suzie, and this is a good thing.
Fraser: And Suzie appreciates it.
Pamela: And so, I wanna thank Jason Graham, Brett Peterman, Newt Sahr, Donald Mundess, William Jones, Father Prax, Scott Bieber, Bart Flaherty, Andrew Stevenson, Kenneth Ryan, Jason Smartski, Matthias Haden, Martin Dawson, Russell Peto, Dan Lightman, Glenn McDavid and Benjamin Davies. Each week we thank a group of our patrons and you’re the ones that came up this week and we are so grateful that you’re part of our community.
Fraser: Thank you everybody. And thank you, Pamela. We’ll see you next week.
Pamela: See ya’ll. Buh bye.
Female Speaker: Thank you for listening to Astronomy Cast. A non-profit resource provided by The Planetary Science Institute, Fraser Cain and Dr. Pamela Gay. You can find show notes and transcripts for every episode at Astronomy Cast. You can email us at info@astronomycast.com. Tweet us @AstronomyCast. Like us on Facebook and watch us on YouTube. We record our show live on YouTube, every Friday at 3:00 PM Eastern, 12:00 PM Pacific or 19:00 UTC. Our intro music was provided by David Joseph Wesley. The outro music is by Travis Surrel. And the show was edited by Suzie Merv.
[End of Audio]
Duration: 32 minutes
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download
As astronomers started to discover planets orbiting other stars, they immediately realized that their expectations would need to be tossed out. Hot jupiters? Pulsars with planets? We’re now decades into this task, and the Universe is continuing to surprise us.
In this episode we mentioned donations. Click to learn more!
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download
Show Notes * A planet that should not exist (unibe.ch) * 18 New Planets Discovered Orbiting Massive Stars (Astrobio.net) * Weird planets (Many Worlds) * Kelt-9b: astronomers discover hottest known giant planet (The Guardian) * KELT-9b (NASA) * Super-Earth Orbiting Barnard’s Star (ALMA) * Surprise! Giant Planet Found Circling Tiny Red Dwarf Star (Space.com) * TRAPPIST-1 system (trappist.one) * ALMA Discovers Trio of Infant Planets around Newborn Star (ALMA)
Transcript
Transcriptions provided by GMR Transcription Services
Fraser: Welcome to Astronomy Cast for a weekly facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me as always, Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hi Pamela, how you doing?
Pamela: I’m doing well, Fraser. How are you doing?
Fraser: Good. There is a typo in my introduction, and I look over it every single time. It says and director of CosmoQuest, but actually you’re the director of CosmoQuest, and I make that mental change every single time. But it’s too difficult for me to go and edit the thing, so I’m just going to keep going. It keeps the mind sharp I think is what I’m saying.
Pamela: It does. It does.
Fraser: Before we get into this week’s episode, are there any interesting things to talk about?
Pamela: Yes. Yes. We have two, two, count them, two things that need to come up. The first one is on October 5th, everyone should go out, look up at the moon, and celebrate International Observe the Moon Night.
The second thing is we have a new podcast over at CosmoQuest. This is the Daily Space. And we are putting out short, roughly 10-minute episodes most Mondays through Fridays that will help you understand the latest news. These are episodes that basically give you a quick rundown of everything you might run across on Universe Today, but get the 30-second version and then go read the three-minute article later.
Fraser: And we’re recording these moments before Elon Musk gives his Saturday presentation on the state of starship, the Starhopper, the newly constructed prototype, which I’m assuming he will stand in front of and tell us what happens next.
So, for those of you who listening from the future, wasn’t that something? All right. Moving on.
As astronomers started to discover planets orbiting other stars, they immediately realized that their expectations would need to be tossed out. Hot Jupiters, pulsars with planets, we’re now decades into this task, thousands of planets and the universe is continuing to surprise us.
Pamela, if he went back 30 years and talked to a person searching for solar systems, for other planets, what do you think they would’ve expected the universe would probably look like?
Pamela: They would’ve said, with probably a great deal of insurance, that it is only medium-sized stars that have planets, that the big ones don’t because they have too much light, and the little ones don’t, because they don’t have enough mass. They would say that solar systems had rocky worlds snuggled up against their stars and had gassy worlds further out. And they would’ve said that planets might even be exceedingly rare. We don’t, but that rareness was always brought up.
Fraser: Right, that planets would be rare. And now here we are, like I said – man, I don’t remember. Was it ’89 when they found –
Pamela: So, the first –
Fraser: – 51 Peg?
Pamela: No. So, the first planet –
Fraser: ‘95.
Pamela: – to 51 Peg was ‘95, and then the first planet in air quotes that you can’t see on a podcast was actually found around a pulsar, and that was during the ’91-’92 school year. So, the first time we found one it was around a dead, compact object, and then it would be nearly half a decade before we got to finding one orbiting a legit star that was a legit planet, and it was a legit planet that looked like nothing anyone had ever predicted.
Fraser: Yeah. Yeah. And totally, totally surprising as you said like when no one would have predicted.
Pamela: And so, the first problem that we had to try and figure out was well, what is the actual distribution of planets. And at this point, we were still thinking only Sun-like stars probably have planets. And so, people started doing all sorts of mental gymnastics figuring out okay, so we can migrate the gas giants in if we do these things and we do this other thing, and we’re not sure how to stop them, but we were good. We were good.
And then, we started looking at more and more kinds of stars. Initially we were limited on what we could discover, because the way we were looking for planets was by looking for the gravitational tugs on the stars that they’re orbiting, which means we could only look at one star at a time using high-resolution spectra.
Well, as we started to look for them using transit searches that looks for the dips in light from the stars a planet passes in front, suddenly we were able to look at large swaths of the sky and multiple stars at the same time, and suddenly we were finding stars by the dozens, by the hundreds, by the thousands, and we were looking because they were in our field of view at a whole new range of kinds of stars.
And this was when we started discovering that pretty much every kind of star that we looked at happened to have a planet if it happened to be high enough metallicity. And suddenly, oh. Oh dear. We had to start changing what we imagined, and the place that we didn’t change fast enough, in my opinion, was massive stars.
Hi. This is Dr. Pamela Gay. I want to invite you to listen to my new podcast, the Daily Space. Most Mondays through Fridays, our team at CosmoQuest brings you a quick rundown of the daily news in space and astronomy. Check it out at DailySpace.org or subscribe using your favorite podcast catcher.
Fraser: Okay. So, let’s – I mean we’ll sort of reevaluate all of those things. So now, as a modern exoplanetary researcher considers what’s out there and in what kinds of configurations. So, let’s start with the massive stars then. So before, stars that big probably didn’t have planets. Now what do they think they have?
Pamela: Well, the original thought was the massive amount of energy given off by a massive star would push back all the material trying to form planets, and planets would not form. But now thanks to worlds like KELT-9b, we know that systems form planets, and those planets could be snuggled up right next to the stars such at poor KELT-9b on its surface has temperatures that look like the surface temperatures of a star.
Now this is not it generating that much heat, it’s getting heated that much from the outside, and it’s cooler on the other side of the planet. We did not think this would be possible, and it was sort of a I’m going to go look for an undiscovered country work by the likes of Scott Galdi that led to people looking for planets around these stars that otherwise weren’t being searched.
Fraser: So, people were like even just not looking at these stars?
Pamela: Yeah. They were just pooh-poohing the idea. Oh. That’s a waste of telescope time.
Fraser: Yeah. There’s no point.
Pamela: Just don’t do that.
Fraser: Yeah. Don’t even look. And now I mean I think that’s nicely reflected in a spacecraft like TESS, which is just like forget it. We’re just going to look at them all. If it’s a star, we’re gonna look and figure it out.
So then, seeing this planet around a much more massive star, then what are the implications for that?
Pamela: Well, it starts to tell us first of all that well, somehow the stuff of the disc is still able to coalesce enough to form planets, and may be that the planet formed out beyond the area that was cleared by the star’s light. And we have this problem of planetary migration that we really haven’t figured out where we keep finding these Jupiters. Where we can’t explain them forming there.
So, somehow they’re gradually migrating towards there star and stopping before they get into their star, and I’m not even going to try to explain that, because I don’t think anyone can explain it.
Fraser: Yet.
Pamela: Yet. It just like – how did you get there? No idea.
Fraser: Yeah. But I mean the timeframe for these really massive stars is so much lower. Like for the supermassive stars, the only live for a few billion years at the most, and then they explode as supernova. You know, some of the in-between stages between us and some of those more massive stars, I mean does it make sense to go looking for planets at Betelgeuse or other super red giants? Blue giants? Things like that?
Pamela: Well, so it’s looking more and more like some planets can potentially form in hundreds of thousands of years based on some of the models they’re kicking around. So you have planets working to form the same time that star systems are working to figure out to star, and so you have the stars, the planets, all of them forming in a mess, and the model that we had even up until a few months ago was you have this disc that is flowing material in torrents that forming star. The star lights up, pushes back, the flow stops, but in that mix, you’ve had planets beginning to form, and the way they’re forming is small dust grains collect together, form bigger dust grains, those dust grains collect together, form a bigger and bigger and bigger stuff until eventually start to get protoplanets in planet-planets.
And when it was thought this is the key, it was thought even a year ago that when we use the Atacama Large Millimeter Array to look at these young star systems, when we see gaps in the discs around the stars, those gaps must be places where planets form, because we didn’t have another way to explain the gaps, and the gaps perfectly fit what we had in our models.
Fraser: So, you’ve got this situation like not – I mean the great thing about say ALMA is it can directly observe a protoplanetary disc from any angle, and there’re some really wonderful images that have been taken with ALMA showing these different discs face on, almost edge on at different angles.
And all of the methods of detecting planets right now, they really require things to be lined up perfectly. A planet passes right in front of the star, yanks it back and forth or blocks the light, but ALMA, we see these records spinning in space or pinwheels for all kinds of crazy shapes and go okay, there’re planets there, and yet there’s also going to be a really hot massive star there like a Wolf-Rayet star.
Something really powerful, and yet you see the planets coming together, and that was not expected.
Pamela: And it’s in these systems with things like T Tauri stars that when you look at them, we can now start also looking at the system where we’ve identified the gaps with ALMA, and we can start using other telescopes that look in the sky in infrared in the colors that planets are giving off the bulk of their light.
And what we’re finding is those planets aren’t always in the places that we thought they would be. We’re finding gaps that don’t have planets. And they don’t even have eddies that say there’s a planet here you can’t see.
And this is one of the amazing things about the resolution of ALMA is ALMA can see not just the gaps but in many cases it can also see the eddies that are left behind by planets. And having found those in some places and not found them everywhere tells us that different things are happening in different places.
Fraser: All right. So, we’ve talked about one sort of whole class of stars and the planets that are around them. Did you want to consider another kind of place that maybe planets were either thought impossible or unlikely?
Pamela: Well, from one extreme to the other, the next place to go looking is those tiny planets or rather tiny stars that we thought had tiny planets. This is where we have systems like the TRAPPIST-1 system that is a red dwarf star that with TRAPPIST-1 is orbited by seven tiny terrestrial worlds.
And so here we have our entire solar system with planets capable of having water on their surface that are probably not habitable with life as we know it, because little red dwarf stars tend to go through violent youth and give off high radiation flares, badness, sterilized worlds, but despite this horrible childhood, these planets are there, and the idea here initially was there’s just not enough mass to have a disc capable of performing planets and okay fine. So that was wrong.
So, now we have this idea of you have a tiny star with a tiny disc, and the tiny disc forms a multitude of tiny planets, and we understood that. And we thought that’s what we would always see. And then today, after we had planned this episode – so this is a well-timed press release, we got news of red dwarf star GJ 3512.
This is an object 12 percent the mass of our sun, and it has orbiting it a plant that is intermediate in size between Saturn and Jupiter. This is a giant planet compared to a tiny, tiny star.
Fraser: Well, I mean just to be fair, the smallest possible red dwarf star is going to have say 70 to 80 times the mass of Jupiter, and you’ve got it something with say twice the mass of Jupiter?
Pamela: It’s half –
Fraser: Oh. Half the mass Jupiter. Yeah. So, it’s definitely a scaled down version of the solar system, but it’s not like you just – go ahead.
Pamela: And our models don’t allow for a system with this mass ratio to have formed the plant through this bottom-up, dust hit’s dust hit’s bigger dust, forms planetesimals, forms planet. That model does not work.
So, now what we’re starting to think is it may be possible to form solar systems in multiple different ways, and that is not nice, universe. Not nice.
So, here we’re looking at perhaps we can get these gas giants forming with these baby stars in what’s called a top-down model where that fragmenting cloud of material that formed the star didn’t fragment into one big fragment that spun up and formed planets around the star, but rather it formed into two fragments side by side, rotating around each other where one of those fragments form the planet and the other one formed the star.
And this is similar to how binary stars form. So now instead of a binary star, it’s a start and a planet.
Fraser: Right. So, when they have a common center of mass is outside of the star? I wonder if –
Pamela: Yeah.
Fraser: – they’re going to be orbiting – yeah, a common point, which would be –
Pamela: So, this is similar – it’s more exaggerated than Pluto-Charon, but it’s a cool system. Yeah. Will call it that.
Fraser: But I mean just the idea. I mean as you said, you’ve got these red dwarf stars. They have this tiny amount of material compared to what a star like our sun does, and yet when you look at say the TRAPPIST system, there are six, seven planets – seven planets known so far. Who knows what else could be orbiting a little above or below the plane of the ecliptic farther out into the solar system.
I mean it is a bustling star system even compared to the solar system. And when you think about the fact that the vast majority of the stars in the Milky Way are these red dwarf stars, you know, mind blown.
Pamela: Well, and beyond that, we’re only starting to be able to sample what’s out there. We still aren’t finding the mercurys. We are just starting to find super earths, which are really some Neptune objects that we optimistically call super earths.
We don’t know the full diversity of what else that is out there, because we haven’t been looking long enough. As you started out by pointing out, this is still very much the early days.
Fraser: Yeah. Yeah. So, I mean I would be interested at this point now, I mean do we have a sense of what a standard solar system looks like?
Pamela: No.
Fraser: Star, planets. That’s it?
Pamela: So, what we have is –
Fraser: Mostly?
Pamela: – we can poke the system from a variety of different ways, and as far as we know, low-metallicity stars. So, these are stars that don’t have a lot of iron. They don’t have a lot of carbon. They don’t have a lot of heavy elements in them.
These kinds of devoid-of-heavy-element stars appear to still be devoid of planets. So, that part of our original understanding was true. If you don’t have the stuff to make planets, you do not make planets.
Fraser: Right.
Pamela: The parts of our theory that constrained little things and big things, totally bogus. We need to figure that out again. The parts of our theory that constrained how big the planets can be relative to the star, totally bogus, need to start over again.
Our ideas of how a disc is able to form and move and migrate planets is really the next big thing that we need try to get a handle on. One of the biggest questions in my opinion in planet-forming models is how do you migrate a planet and then stop its migrations?
The simplistic model that we’ve been using is you have a disc. The very center of the disc is empty, because the early stars’ light cleared out the center of the disc, and when the migrating-inward star runs – not star, the migrating-inward planet runs out of material to interact with frictionally, it stops migrating.
Fraser: So, I mean this idea of these migrations, I mean they actually can happen really quickly. I’ve heard that you can actually move your planets on the order of tens of thousands of years once they’re drawing and material from one side of the disc of the stream that they’re in, and depending on sort of where the material is coming from, they will absorb it onto their body, and at the same time, this induced a torque that moves them quickly. But here in the solar system, our planets moved outward, right?
Pamela: And this is another one of those confusing points. So, when we see the youngest planetary discs out there, we’re looking at discs of material that are massive in radius compared to the size of our own solar system.
So, there seems to be this two-step process where you migrate the material inward while consuming it into planets or something, you end up with a smaller solar system based on this much larger distribution of material, and then once you have all your planets in the middle, you fling them back outwards.
And this isn’t something that you see talked about in general. What you see is the observations from ALMA of these 10s, over 100 AU planetary discs. Then you see systems like the one we live in that are 55, 60 AU before you start running out of planets and Kuiper belt, and you also see of course all the solar systems with the hot Jupiters in the center.
And dynamically, we have models for our solar system. And that the bottom of everything I say today, your take-home message should be model could be totally wrong.
Fraser: Right. Well, yeah. And so, just I mean part of this conversation is like don’t we have a bit of an observational bias?
Pamela: Yes.
Fraser: I mean the fact that the first thing is found were hot Jupiters is because they’re easy to find. If you ask me to find trees, I will find you Douglas firs until you’re sick of Douglas firs until you’re like fine, you know, enough Christmas trees. Thanks. I got it. And maple trees. I can find you Douglas firs and maple trees.
Pamela: I have gum trees and oaks.
Fraser: Yeah. There you go, right? And so, they are close. I can walk outside and I can find a bunch of them for you right now. And so, we have this observational bias of big planets orbiting closely to small stars.
As the capability of the tools change over time, are we starting to see some kind of shift to get a better sense of what’s normal? What the new model might be?
Pamela: I’m not sure we’re ready to say what is normal. I think we’re ready to say that we were wrong. We were just wrong.
Fraser: Good. That’s a start.
Pamela: You know, it’s an important start. One of the reasons that scientists do science, and I’ve said this before, and I’m going to keep saying it, is because we don’t know all the answers, and we really want to. These new results with ALMA are going to form the foundation of here is the beginning of what solar system models should look like.
Right now, we’re looking at a few high-resolution images. We need to get to a few hundred before we have statistical distributions. We’re only starting to find planets around tiny stars, and tiny stars make up the bulk of our galaxy. These are the stars. And they’re awesome. And we’re still learning new things about our own solar system.
We are starting to understand that you can explain the size of Jupiter’s core as the result of Jupiter getting whacked hard four billion years ago.
Fraser: Right.
Pamela: This is new information in the past few months, and by realizing that our galaxy – we knew our solar system had been a supervisor in place. We knew that. We can look at the moon and see that, but to see it in the size of Jupiter’s core, to see it in how we recognize other worlds now, planetary solar system formation is far more complex and violent of a process of things moving in and moving out than we ever imagined, and I’m starting to see it like it’s a really bad square dance done right children who don’t hear the caller over the music very well.
Fraser: But do you foresee –
Pamela: That is my best modern analogy for planetary formation.
Fraser: I’m going to need a different one. I need you to go back and keep work shopping it.
Pamela: Okay.
Fraser: Do you foresee this time when astronomers will have a standard model of planetary formation where you take the mass of the star, the metallicity of the star, you take the – punch that in and out comes a reasonable expectation of what kind of a planetary system you will probably find around it?
Pamela: We need to come up with some cool constraints. These include things like you need to know the metallicity of the star. You need to know the size of the star, mass, temperature, all of that. It’s sort of like one thing. And then going into it, you need to understand what is the molecular cloud that’s fragmenting up? Are we looking at something that’s rapidly collapsing because it took a hard knock, or is it more gradually collapsing?
We don’t yet know how things like that can affect the formation rates in terms of massive open clusters end up with one distribution of – we know the end up with one distribution of stars. They have one initial mass function, but do they also have a different planetary initial mass function? We don’t know how the distribution of planet masses compares from two different stars of the same type that formed into different environments. These environmental effects are going to be a whole lot harder to get at.
But with ALMA today and the Square Kilometer Array coming in the future, we’re gonna have more and more potential to get there. And when if JWST ever launches, that’s –
Fraser: It’ll launch.
Pamela: – and function –
Fraser: Don’t say if. It’ll launch and function. Don’t you say those words. It’s gonna happen.
Pamela: I’m going to be cautionary, because if I’m pessimistic, it has to work to prove me wrong.
Fraser: I can’t wait until we do an episode on James Webb. It’ll happen.
Pamela: But there’s the ability in the next decade for us to get the data that is needed to constrain our models and to encourage our creativity, because both things need to happen.
Fraser: And we will bring every part of the story to you as the evidence is discovered and the previous theories are overturned and nature reveals its mysteries one after the other. So, thanks, Pamela. That was awesome.
Before we go, do you have some names that you may want to say to thank our generous patrons for their ongoing support?
Pamela: Yes. We have some wonderful patrons that allow this show to happen and allow us to pay Susie to take care of us and take care of all the well, day-to-day activities around CosmoQuest.
And those who are making all of this possible are Mathias Hayden, Ron Thorson, Brandon Volverton, Gregory Joyner, Rachel Fry, Darcy Daniels, Eric Ferenger, Kelsely Penflinko. You guys are welcome to give me pronunciations. I’m so sorry. Ryan and James, Kristin Brooks, Duane, Isaac, Shannon Humbart, Dean, Glenn McDavid, Dan Littman, Paul Veller, Martin Dawson, Russell Petto, Kenneth Ryan, Bart Flaherty, Jason Graham, and Brett Peterman. Thank you.
Fraser: Thank you everyone. All right. We’ll see you next week.
Pamela: Bye-bye.
Susie: Thank you for listening to Astronomy Cast. A nonprofit resource provided by the Planetary Science Institute, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at Astronomy Cast. You can email us at info@AstronomyCast.com, Tweet us at Astronomy Cast, like us on Facebook, and watch us on YouTube.
We record our show live on YouTube every Friday at 3:00 p.m. Eastern, 12:00 p.m. Pacific, or 1900 UTC. Our intro music was provided by David Joseph Wesley, the outro music is by Travis Suro, and the show was edited by Susan Murph.
[End of Audio]
Duration: 32 minutes
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download
Relativity is used in more day to day situations than you may realize. In this episode, we will count (some of) the ways. This episode is brought to you live from the All-Stars Star Party in Indian Wells, California
In this episode we mentioned donations and tours. Click to learn more!
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download
This episode is sponsored by: MagellanTV and Barkbox
Special offer – Visit www.barkbox.com/gift/claim/code or www.barkbox.com/super-chewer/gift/claim Use Code – BPGC1V8IF8CMO to receive your first box! No credit card information necessary. Gift Subscriptions do not auto renew. Can only be redeemed by US or Canadian residents. Cannot be combined or applied with any other promotion/offer. Cannot be applied to an already active subscription.
Show Notes
Bennu Mappers – Help CosmoQuest map rocks to help pick which ones OSIRIS-REx will bring back from asteroid Bennu! Start your coffee pots, get your favorite mouse/trackpads, & GET MAPPING! http://bennu.cosmoquest.org/
Theory of Relativity
What is a gravity well?
681: Gravity Wells from XKCD https://xkcd.com/681/
Gravity Well demonstration
Gravitational Redshift
4 Ways You Can Observe Relativity In Everyday Life
Einstein’s Relativity and Everyday Life
8 Ways You Can See Einstein’s Theory of Relativity in Real Life
Science Fiction or Fact: Is Time Travel Possible?
Twisted Physics: 7 Mind-Blowing Findings
Transcript Transcriptions provided by GMR Transcription Services
Pamela: Today’s episode of Astronomy cast is sponsored by Magellan TV. Claim your two-month free trial only available at Magellan TV dot com slash astronomy cast. Magellan TV is a brand-new streaming service that features the very best collection of space and science documentaries available anywhere.
The service includes over 1500 documentary movies, series, and exclusive playlists designed with you in mind. Check out their space genre and explore the solar system like never before. If you’ve been listening to our last few episodes, you know that we’ve covered a mix of ethno-astronomy, discussing the sky stories of people around the world, as well as highlighting modern observatories that circle our globe.
This mix of old and new reflects the content I’ve been consuming on Magellan TV. Where I can catch the latest news and archaeology, and anthropology, and also the most recent documentaries about our universe. This is a platform founded by filmmakers, that will help you gain insight into the things you are passionate about as you consume their productions, one awesome episode or film at a time.
Find the answers to some of the biggest questions about the universe, and gain a deeper understanding about our solar system, astronomy, the cosmos, novas, and beyond. These are the stories of Magellan TV. Once again, claim your two-month free trial, only available at Magellan TV dot com slash astronomy cast.
Fraser: Astronomy cast episode 536. Everyday relativity. Welcome to astronomy cast. Your weekly fact-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of universe today, and with me, as always, is Dr. Pamela Gay. And I don’t have an introduction in front of me, so you are going to have to say your title.
Pamela: I am Dr. Pamela Gay. I am a senior scientist at the Planetary Science Institute, and the Director of Cosmoquest. And you should all be mapping boulders at bennu dot cosmoquest dot O-R-G.
Fraser: Man. Stop yelling at them.
Pamela: I really need them to map boulders and rocks and craters. Please?
Fraser: So, we are recording this episode live from Indian Wells, California, as part of the all stars party astro tour. We said that this episode of astronomy cast had ended. That we were going on hiatus. That was a lie. This is a bonus surprise. Enjoy. Maybe there will be more things. Who knows? This is going to be a weird summer.
But you missed this one, unless you are here, but then listened afterwards. That is weird. But if you want to come on the next trip, I am going to be going to Iceland in January 2020. So, just go to astrotours dot C-O. They are taking reservations now until the middle of July. So, if you ever wanted to go aurora hunting with me, and also glacier hunting, and also Icelandic troll hunting, you should definitely go to astrotours dot C-O and sign up.
We had a great time last time we went, and it was crazy storms. We didn’t see a lot of auroras, but I think this time it is really going to work. So, astrotours dot C-O, and sign up. All right.
So, relativity is one of the most mind-bending concepts a human can attempt to contemplate. How can different places experience different speeds of time? Well, good news. You are taking advantage of it right now thanks to the handy gadgets like your phone. Pamela, you wanted to talk about some of the super weird ways that we actually incorporate relativity into our lives every single day. But before we get into some of that, let’s just talk about relativity. What is it?
Pamela: It is a set of theories most famously worked on by Einstein. Worked on actually by a whole bunch of people working together. And it describes, literally, our place in space and time relative to one another. And it turns out that even though we are so close, I am not seeing you right now, because it takes the photons of light bouncing off of your body a moment to reach me.
And as I look out further and further, looking at people in successive rows, I am seeing them further and further back in time. And as those photons gravitationally interact with things around the universe, their paths get bent and distorted. And that gravity field, well, there is some weird stuff that happens. Because no matter who you are, no matter how fast you are going relative to something else, all of us see those photons moving at the exact same velocity.
Fraser: All right. So, let me just understand this for a second. So, I am moving – whatever – at 100 kilometers an hour. You’re moving 10,000 kilometers per hour. Someone is moving just a fraction away from the speed of light. And we are all watching a laser beam that has been shot from the International Space Station, and we are all watching that laser beam, and we are measuring the speed of light of that laser beam as it moves through space at the speed of light.
Even though we are all moving different distances. And I mean, I guess, in our everyday experiences, that is not what we experience with, say, a bullet being fired. If you are moving close to the speed of light, and I am moving at 100 kilometers per hour, we see a bullet moving at vastly different speeds.
Pamela: And just in more practical terms, when we are going down the highway, we see the cars that were passing moving relative to us at ten or fifteen miles per hour, unless you are a crazy person. But if you are standing on the side of the road, you see those cars going 60 to 90 miles per hour.
And this difference in how we perceive velocities of cars, velocities of runners relative to our own motion, is not true with light. No matter who or what you are, light is going 300 kilometers per second, and that is the law.
Fraser: Right. So, this is, of course, the amazing discovery that Einstein made, and I am sure that someone could have thought of it earlier, because it is so weird, right? That time is the thing that changes.
Pamela: This episode is brought to you by Bark Box. For a free extra month of Bark Box, visit W-W-W dot Bark Box dot com slash astronomy. When you subscribe to a six- or twelve-month plan. As a lot of you know, I’ve got two dogs; Eddie and Stella. Eddie was my reason for getting Bark Box, and month after month he devoured the two large treats, played with the themed toys, and I would train him with the other made in America and in Canada tasty, healthy goodness that came packaged in every box.
For years, Eddie loved on his Bark Box stuffed toys, and these high-quality playthings went through the wash after wash after wash and came out looking awesome. And then I got Stella. She is small, and she is mighty, and she likes to shred things. For her, there are extra heavy chewer toys. She actually managed to get one toy open, and its spiky ball core, well, it was like getting a whole new toy.
I love Bark Box, and Stella and Eddie think your furry friends will love it too. Once again, for a free extra month of Bark Box, visit W-W-W dot Bark Box dot com slash astronomy, and get that box when you subscribe to a six- or twelve-month plan. Your furry friends will thank you.
Fraser: So, fine. And it is not like this hasn’t been proven a million times. Einstein is still right. So, then, what are the practical applications. How do we actually experience this? Are we experiencing time dilation as we are moving around in regular life?
Pamela: Yes. And where is starts to matter is once upon a time, we were worried about whether our pocket watches were closely enough aligned to keep the timetables of the trains in Europe.
But nowadays, when we are trying to get a satellite hook up to bring two news stations across the world together, we need to sync up those radio waves so that something that has a millimeter wavelength lines up on the other side of the world. And this requires more accuracy than your pocket watch is going to have.
Fraser: Yeah.
Pamela: And as we work out all these timings, we have to take into account the fact that where we are on the surface of the earth, we are experiencing a whole lot more gravity than the space signals are going off of. And this creates one sort of shifting light and shifting time.
Those spacecrafts are moving at a different rate around the earth’s center than we are as the earth rotates. That creates another expansion of time.
Fraser: Okay. So, hold on. Those are two separate issues that maybe we should break up, right? So, there are two factors that will impact the amount of time that you experience. Gravity wells, and velocities. Can you explain that?
Pamela: So, with a gravity well, gravity is going I shall hold on to you. And the light, as it tries to get away, actually gets red shifted. As you look into a black hole, you see things getting redder and redder as it falls in. And part of this is doppler shifting, and red shifting, but gravity is also playing a role.
As you pull out of the gravity well, that pull gets less, and light is getting affected less. Time is getting affected less. And so you have a difference due strictly to how far you are from the center of mass, and how fast your clock is ticking.
Fraser: Right. And the practical application for this – if you want a way to sort of think about it is think about the movie Interstellar, because they gave us this example. Spend some time near a supermassive black hole. Spend an hour, and you come back, and it has been 40 years for the people that you left back at home. And so, we, down here, on planet Earth, are experiencing less time than people who are out in space.
Pamela: If they are stationary.
Fraser: If they are not moving. Yeah. They are stationary. Yeah. Yeah. People who are out in space, relative to us. They are not moving, but they are just out there in space. They experience – woah. So, do we see them moving in slow motion? Do they see us moving in slow motion?
Pamela: They would see us moving in slow motion, but the catch is, you would fall out of orbit if you tried to do this. It would be very messy. Don’t do this.
Fraser: Right. So, just before they plummet to their death, they notice that we are moving ever so slightly a little slowly. That is weird, and then the screaming, and then the burning.
Pamela: And the death.
Fraser: Yeah. Okay. So, that is the one half of it, and then the other half of it is the velocity.
Pamela: And this is that twin paradox that they played with, with Scott and Mark, the two twin astronauts whereas Scott went around and around the earth, his velocity – he was accelerated to a higher rate of motion. And you look to see who did the acceleration to figure out whose time was shifted. You look to see who was accelerated. Scott was accelerated.
If he wasn’t, he would still be on the planet. This experiment wouldn’t have worked. He went at the higher velocity, and because he was moving faster, in order for him to see light traveling at the same rate, his clock has to slow down. The way I remember this is he was Buck Rogers in the 21st century but didn’t quite get there because he wasn’t going fast enough. Buck’s time slowed down, thus he made it.
Fraser: Right.
Pamela: So, the person who is on orbit, their clock slows down, they visit the future.
Fraser: So, then, is there some perfect balance point where – because the astronauts are moving at 28,000 kilometers per second. That is way faster than us. So, they are experiencing – so, we would see them moving in slow motion, but they are outside of our gravity well, and so then, they would see us moving in slow motion. So, is there some point where they balance out?
Pamela: Yes, but not with the earth, because we would fall out of orbit. If you go to something that has a greater mass, you can find that balancing point where the gravitational red shifting, and the time due to your velocity and acceleration, where those two counteract each other. Just not here, do that. There, we can’t get there yet, so maybe don’t do the experiment.
Fraser: Right. Right. And I know that when we look out to the other side of the entire universe – the very edge of the observable universe, that is as far as things can go. And those places have actually experienced 30,000 years of time different to us because they are moving away from each other. Like, time has no meaning.
Pamela: No. It doesn’t.
Fraser: Yeah. All right. So, then now your head is like come on. Prove it Fraser and Pamela. Fine. We are going to prove it. What are some of the practical applications how relativity has moved into our lives every day?
Pamela: Pokemon.
Fraser: Pokemon. I got to catch them all, but they are moving in slow motion.
Pamela: We are here when we could be out for the adventure day. And we are both Pokemon Go players.
Fraser: You are, like, a serious Pokemon guru. I mean, I dabble. You are hardcore.
Pamela: Right. I am.
Fraser: So, fine. Why could I not play Pokemon Go?
Pamela: No. Well, you could, but it wouldn’t know where you are, and you couldn’t catch them all.
Fraser: Right. You’ve got to grab that Pokestop right now.
Pamela: I’m totally spinning – I got a gift. I will send you a gift.
Fraser: Will you send it to me? Okay. Great.
Pamela: Yeah. Yeah. On wizards unite, I play that as well. I – Nayak, you are a problem in my life. So, these things that we do with augmented reality that paint our world with games, with information that rely on few meter accuracy and our position on the planet, all of these things have to take into account that we are latching on to three to five satellites that are high above our heads.
And if we weren’t latching onto those satellites, we wouldn’t have this accuracy. But those satellites are moving. And so, we have to do the relativistic corrections to the times, or we would be misplaced in time and space, and all of these things that are fun, informational, and prevent us from getting lost – Google maps. Thank you.
Fraser: Okay. So then, how does that work then? So, your phone knows what time it is? And how does relativity affect your phone?
Pamela: So, you latch on to three different satellites – or five – three to five satellites to get your position. If it is only two, you don’t know where you are. Your phone, your watch, whatever it is latches on to three different satellites that are zipping in slightly different directions, all have different light travel times to reach your phone, and your phone listens to the time the satellite sent the signal, compares the times for the three different signals, looks to see where the satellites thought they were when they sent the signal, does a relativistic correction.
Using that relativistic correction, it goes the satellites, when they sent this signal, were actually these three places. I now know my separation to three different points, and with three points, you can figure out where you are in x, y, and z. Left, right, up, and down. So, you are literally drawing three measuring sticks between satellites and using relativistic corrections.
Fraser: Okay. So, your phone –
Pamela: Instantaneously.
Fraser: Your phone detects satellite one is moving towards you, and goes oh, you are moving towards me. So, time, you are moving in slow motion. Therefore, the time that you think you are sending the signal in not the time that I’m actually receiving the signal. I’m going to make an adjustment. But then that other satellite that is over there, that is moving perpendicular to me, is experiencing a different thing, and ultimately you are out of the gravity well, to a certain extent.
And it is calculating the velocities of all of these different – and the positions, and the directions it is going, and then it is accounting for that. And so, then, if you didn’t take Einstein’s equations into calculating your position on Earth, would GPS work at all?
Pamela: No. Not really. I mean, it would roughly tell you where you are.
Fraser: You’re on Earth.
Pamela: Yeah. And let’s not try. We know, because of Pokemon Go, relativistic equations make our lives at least a little more, well, wiggly.
Fraser: All right. Okay. So, fine. So, our phones, literally – I mean, for those of us who aren’t playing Pokemon Go – those of us who depend on, say, turn by turn driving directions, or hiking into the forest, again, you need your GPS to be accurate.
Pamela: Oh, yeah. Yeah. Yeah.
Fraser: Yeah. So, again, it is so funny. Like, you have a conversation with someone who is like I don’t believe Einstein. Like, fine. Then, throw away your phone. Give me your phone, actually, doesn’t believe in Einstein. I will take your phone, please. And we’ll go from there. All right. So, what else?
Pamela: Gold.
Fraser: Explain how.
Pamela: This is one of my favorites. So, if you’ve ever looked at the models they have of the lunar landers, there are a whole lot of shiny gold on that stuff. And this is fairly thin, fairly pure actual gold. And as it is sitting there, hanging out, going I am scattering mostly yellow light.
The reason that we see it the color that we see it, and part of the reason that it makes such a fabulous radioactive particle deterrent is that you have this extraordinarily dense atomic core, and this extraordinarily dense atomic core means that the photons that it interacts with, it preferentially shifts their colors as they interact down in the core, and we end up with less UV and blue light then we would if it didn’t have this dense core. And thus, more yellowy gold than we would without relativity.
Fraser: But how is it due to relativity?
Pamela: So, one of the awesome things about relativity is it talks about how light gets bent in these high density situations, and then you start getting into these affects of as you get in so close, everything is so dense that the physics goes out of norm. And if you try to use Newtonian physics to describe the motion, Newtonian is like no. Just, no.
I am going to misplace those photons and change the color. But with relativity, you can start to figure out how the momentum is changed of the photon. How the length has changed over the photon. All of these factors together, and gold, unless it has a lot of impurities, is going to give you a yellow refection.
Fraser: But I mean, it is not just gold, right? It is going to be any heavy element pounded into a thin film that has a lot of protons down thee in the core, right?
Pamela: And it gets even weirder when you start looking at things like Mercury. Mercury flows like a liquid, reflects like a mirror. And the way that it is able to do all of this is it was due to its super high-density core again. And so, with Mercury, again, super high-density core, super weird physics, super awesome material. So, anytime you broke a thermometer, and your teacher didn’t’ catch you fast enough, you played with the mercury?
You were playing with relativity. You can say you experienced it while also experiencing a toxic substance. Don’t play with Mercury.
Fraser: Right. Right. But like, I’m just trying to imagine what the density of the material impacts the relativity, and the –
Pamela: So, think about a black hole is a high-density thing. It changes the physics we work with.
Fraser: Right. But isn’t that from the mass? Or is it from the density? Or, is that the same thing?
Pamela: Well, it is in many ways the same thing. You can have a star with ten solar masses of material, but it is not a black hole because the density is not such that you can get close enough to the sun. Yeah.
Fraser: Right. Right. Okay. I see. I see. So, it is the density that is actually doing the heavy lifting.
Pamela: Yes.
Fraser: Right.
Pamela: And there are other places that I did not realize that we have to make relativistic corrections until I started doing research to prep for this show. And one of those things that I made in school was an electromagnet. You wrap a whole bunch of wire around your fingers. You use your other hand to attach the wires to the battery.
You don’t really shock yourself. Some of the electricity goes through your hand. Most of the electricity hopefully goes through the wire. And you can drag things around on the surface of your desk.
Fraser: With you hand?
Pamela: Yeah.
Fraser: Wait. Wait. Wait. Wait. Wait. You can – I’ve never done this. Like, I’ve coiled it around with a nail. Yeah. You take a nail, and you coil a copper wire around the nail, and then you attach the two sides to a battery, and you create an electromagnet. Congratulations. There is your science fair project. But you say you can do this with your hand? With your finger?
Pamela: So, you – it is just like you are winding up yarn, or cables, or something. You wrap the wire around your fingers. You have a loop of wire. You pull the loop of wire off of your fingers. You don’t keep the loop of wire on your fingers. You then grab a battery and hold the two ends of the wire on the battery. If you were in a cheap school, like the one I went to, and you don’t have battery cases, and you have an electromagnet, you don’t require the nail to make the electromagnet. You require the coils of wire.
Fraser: So, are you like a meat magnet?
Pamela: Yes. Yes.
Fraser: Neat. A magnet made of meat. All right. So, fine. Magnets. We are talking about electromagnets.
Pamela: We are talking about electromagnets.
Fraser: I’m intrigued.
Pamela: Now, if you have current running through a wire, moving charge generates a magnetic field. And if you have two wires next to each other, that have current – my arms can’t do that, for the people who are watching – if you have current with flowing in opposite directions in two parallel wires. You can get those wires to attract each other. You can get those wires to repel each other. And to really figure out how much of this is going on, you have to do relativistic equations.
Now, when we teach this to freshman in university, we leave those corrections out, because in the grand scheme of all the friction and everything else your standard electrical engineer is going to have to deal with, these are not a problem. But as we get into building faster and faster electronics, with more and more delicate wires – a super delicate wire that is getting yanked on by electromagnetism, well, you can wreck your circuit. So, you have to start worrying about these detailed effects.
Fraser: Right. But that was the force. Like, there was definitely a force that is applied to a wire, and same thing. You have a wire and you apply electricity through the wire, and it goes through the coil, and it will yank like a magnet. But I don’t understand where the relativity of this comes in. Is it that the –
Pamela: Electrons are moving close to the speed of light.
Fraser: Right. Okay. So, we’ve got something that is moving close to the speed of light, and you’ve got things going various directions in a computer at close to the speed of light. And in different, and in some cases moving from one spot to another spot, and when they move really close together, when you are looking at just a nanometer apart, they are interfering with each other, and experiencing time dilation and relativity.
Pamela: And it is in figuring out how strong the magnetic field is that you have to start to look at how fast the charge is moving. Any of us, if we are really bored, can put a natural magnet inside a coil, and reverse this experiment and generate electricity by shaking a tube with a magnet in it that goes through the wires. I am not going to do the hand gesture for that. And this generates current.
Now, we are not moving the magnet that fast. The faster we move the magnet, though, the more current is created. The faster the current moves, the more magnetism is created. As we get current flowing faster, you have to take into account relativistic effects.
Fraser: So, would like really advanced – modern computers, they are taking that into account, right?
Pamela: Yes.
Fraser: And they are running at whatever clock rate that they are – the heartbeat of the computer – as it is performing it’s instructions, it is taking into account the relativistic accounts of all of those electron moving around inside the computer to make sure that as it is sending out instructions, and instructions are coming back with the answers, it needs to account for the time dilation for this.
Pamela: The manufacturers do all of that when they are building it.
Fraser: Yes. Of course. Of course.
Pamela: And then it is out of mine.
Fraser: Yeah. No. You don’t specifically have to deal with it.
Pamela: My processor isn’t worried about that. And it also becomes a problem when you are worrying about super conductors. And the faster we get things going, the faster we get our information from point a to point b, the more we have to worry about the corrections we need to make to what happened in the process of getting from point a to point b.
Fraser: That is amazing.
Pamela: And just in general, when you are firing an electron around, that electron is like hi. I’m going fast. Relativity matters. And old CRT televisions, they were firing electrons at the surface of that cathode. So, you have a ray of electrons –
Fraser: A beam.
Pamela: – going through a tube to hit a cathoid, otherwise known as a cat’s electric table – a heated table as far as I can tell – a cat. Cats like to sleep on CRT’s. Modern cats don’t have as much luck, and this is why they claim our keyboards.
Fraser: Right. Right. But so, like, an old television, you’ve got an electron beam. You’re one step away from your own large hadron collider there. You’ve got a particle accelerator in your house firing a beam of electrons in your general direction to entertain you.
Pamela: Yes. Getting stopped by that screen.
Fraser: By that screen. But you’ve got something that is moving at some dramatic percentage of the speed of light, and so you are going to have to take into account relativity.
Pamela: Especially when you are literally painting the screen with that beam using the magnets inside to direct the beam to vary the intensity so that you see different amounts of light, and different colors getting triggered in different places on your screen.
Fraser: I kind of imagine a cathode ray emitter is firing off these electrons, but it is accounting for the time dilation that each one of these particles is going to be receiving to make sure that it all comes together for us at exactly the right time. And if it didn’t make those kinds of modifications to the timing, television would suck.
Pamela: Yeah. And it all ended up in how they shaped the magnets was dictated by relativity. So, if, like me, you have an old cathode ray television in your basement because the garbage man won’t take it. And Goodwill won’t take it. And no one will take it.
Take it apart and look at the magnets. Look at the cathode ray. And the recent ones aren’t as fun as the ones that might be in grandparents’ basements or attics. But these were electrons going at 30% of the speed of light. And it matters.
Fraser: All right. Awesome.
Pamela: And other than that, we just have to look at things like the sun.
Fraser: Mm-hmm. Right. And we know that the sun is eight and a bit – eight minutes and 20 seconds away, or something like that. So, we are seeing the sun as it was eight minutes ago. That is fine.
Pamela: But more importantly, if relativity didn’t work, nuclear reactions wouldn’t work. Our sun would not have a power source.
Fraser: Right. Right. Fusion.
Pamela: And without a star, we would probably be dead.
Fraser: Okay. Fine. Right. But I will give you that. I appreciate my existence. Thanks sun. I apologize for all of the things I’ve said about you in the past. Your terrible heat. It’s okay. Okay. Fine. But how does fusion require relativity.
Pamela: This is the look of where do I start? That required ten years of university.
Fraser: Also, you’ve got three minutes.
Pamela: Yeah. That too. So, ah. Collisions of particles rely on relativity to dictate how things tunnel from a to b. Lower the energy barriers and allow the things that aren’t dictated by quantum mechanics to work. If it is not quantum mechanics, it is relativity that basically describes the sun.
Fraser: Perfect. I feel like I just got my degree. Ha ha. In your face education. All right. I think we’ve reached the end of the time we have here today. So, I think the point here that we should all really take away is thanks to Einstein. You were right again. And thanks to relativity, every day our lives are made better by the mind-bending concept of relativity.
Pamela: Go catch those pokemon and thank your GPS.
Fraser: Yeah. Nobel prize winning concept to help you catch pokemons. Did you have any names with you, or should we just generally thank all of our patrons? Thank you so much for this bonus thing.
Pamela: Yeah. So, I don’t have any names with me right now to read out. Now, we are going on hiatus. This doesn’t mean the work stops. We are going to be working to plan out our next year. Suzy is spending the summer going through and cleaning up our website, setting everything up.
And to thank all of you for kicking around, we are probably going to be sticking lots of bonus randomness into the feed, and we will be returning as we always do with dragoncon, and whatever Fraser is doing come September. It is changing for the summer, but we are not going away, and we would not be able to do what we do without all of the people who support us on Patreon dot com slash astronomy cast. You allow us to pay Suzy a livable wage for everything that she does.
Fraser: Thanks Suzy.
Pamela: Thank you Suzy. And she puts up with so much from the two of us. And thank you. I just kind of don’t know what to say.
Fraser: All right. Yeah. And we will see you on the – maybe not until September. Or maybe, surprise, something else will happen.
Pamela: Surprise.
Fraser: All right. Thanks everybody.
Pamela: Bye bye.
Suzy: Thank you for listening to astronomy cast, a non-profit resource provided by the Planetary Science Institute, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at astronomy cast. You can email us at info at astronomy cast dot com. Tweet us at astronomy cast, like us on Facebook, and watch us on Youtube. We record our show live on Youtube every Friday at 3:00 PM eastern, 12:00 PM pacific, or 19:00 UTC. Our intro music was provided by David Joseph Wesley. The outro music is by Travis Surl. And the show was edited by Suzy Murph.
Interviewee:
Interviewer:
.
[End of Audio]
Duration: 36 minutes
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download