The solar system is a big place, and while Colin's testing the shuttle, Sarah and Matthew have a visitor.

David drops by to explain a bit about relativity and distance within the solar system and the universe in general.

And watch out for mighty Zordon of the Orcs.

Things to Learn

• What happens when you're travelling close to the speed of light?
• What's a light second?
• How fast are you travelling right now, and why don't you realise it?
• Why do two trucks seem to take ages over passing each other?