Just 12 people have walked on the Moon and they'll know better than anyone just how big (or small) the place is. But we can make some comparisons with things on Earth to get a measure of the Moon.
If you've ever wondered why you can look at a solar eclipse and why it can harm your eyes, the answer is in the sun's rays.
For centuries, scientists have known when and where eclipses will be visible. They pack their bags, head for the line of totality and hope for the best – which doesn't always happen.