Maggie, the beagle, is all ready to head to Mars! There's one last task before she starts her journey...

• Miles and Kilometers We usually measure distances in miles or kilometers, but they are small compared to the Mars-Sun distance. Measuring distances within the Solar System using these units result in huge numbers with lots of digits. Not very convenient!


• A.U. stands for Astronomical Unit, which is the distance from the Sun to the Earth. Measuring in A.U. makes the distances nice small numbers, but calculations involving A.U. aren't very natural for most people.


• Light Minutes You've probably heard of a Light Year, which is actually a unit of distance (not time!). It's how far light travels in a year. That's useful for measuring the distances between stars, but it's too big for measuring distances within the Solar System. A Light Minute is better. This unit tells you immediately how long it will take for radio signals or light to travel across the Solar System. The Earth is about 8 Light Minutes from the Sun, which means it takes light (or radio waves) about 8 minutes to travel that distance. See? Very useful!

Drag out rulers, line them up, and measure the distance from the Sun to Mars! If your workspace gets messy, just drag things into the trash bins or use the CLEAR button to start fresh. Enter your answer (and units!) in the box next to each spacecraft. Every unit that you answer correctly increases your clam salary by 1 clam!