Can you estimate how large the Moon is, using only the image of a lunar eclipse shown here? (Image taken by L. Weatherwax at W. Anchorage HS in Alaska, using a MicroObservatory telescope in Cambridge, MA.)

Here are two things you'll need to know: You're looking at the shadow of the Earth as it passed across the full Moon. The Earth is about 8000 miles in diameter.

You might want to think about the following: How big a shadow does an object cast (in this case, the Earth)? Does it depend on how far away the light source is (in this case, the Sun)? You might want to experiment with your own shadow. Is the Earth's shadow the same size as the Earth?

CHALLENGE #2:
HOW HIGH THE MOON...?

This one's on the Starfleet Entrance Exam: If a cow jumped over the Moon, how far would she have to jump?

Using just the telescope and your brain, can you figure out: How far away is the Moon?

For several different ways to do it, visit the MEASURE THE UNIVERSE challenges.

From Earth, you can only see one side of the Moon...ever! The other side never rotates into view. Your puzzler:

From the Moon, can you only see one side of Earth? If not, how long would you have to watch to see all of the Earth?

PUZZLER #2:
THE EARTH ALSO RISES...
OR DOES IT?

Summer night by the ocean... you're watching the Moon rise slowly as the night passes. Cut to: You're sitting on the Moon, watching the Earth rise. Or does it?

Does Earth rise when seen from the Moon? If not, why not? If so, how fast?

Yes, you can solve this one. Show us how!

CHALLENGE #3:
INCREDIBLE SHRINKING MOON... part 1.

You're sitting on a beach, watching the Moon rise. It looks big. Really big. A few hours later it looks small... a lot smaller. What's going on?

This challenge will stump the experts:
Is the Moon on the horizon really bigger than the Moon when it's higher... or is that just an illusion?

Use the telescope to find out. Take an image of the full Moon when it's just above the horizon. (Check your local paper for the time of Moonrise.) Then take an image six hours later, when the Moon is high in the sky. Then measure the diameter of the Moon in both images. We guarantee you're in for a big surprise!

Does the Moon move around the Earth in a perfect circle? (You wish! Nothing's perfect in nature.)

The challenge is: How much closer is the Moon at its nearest to Earth than at its furthest? One mile closer? Ten thousand miles?

To find out, try taking images of the Moon throughout its 28-day cycle. Then measure the images to see if you can find a change over time. One caution: Your images should all be taken when the Moon is at the same height in the sky. (To see why, draw a rough picture showing the Earth, you, and the Moon and its orbit. You'll see that the distance from you to the Moon depends on the angle at which you're observing.)

We'll give you a hint: Antarctica. Over a dozen pieces of moon rock have been discovered in the frozen wastes of Antarctica.

Your challenge: How in the world did pieces of the Moon get to Antarctica?

This is not as simple as it sounds. Click on the image you think comes closest to the actual color of the Moon. (If you had a sample of the Moon's surface sitting on your desk, which of these images would look most like the sample?)

Can you tell the time just from the shape and orientation of the Moon?

Using your own observations of the crescent Moon, along with images from the telescope and a model of the Earth/Sun/Moon, see if you can figure out the connection between orientation of the crescent and time of day. Send us your images and we'll compile an archive... a "Moon clock"!