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Name: Unknown
Status: educator
Age: 30s
Location: N/A
Country: N/A
Date: 5/24/2004


Question:
If you were standing on the moon would you be able to see the Earth spinning? This question was asked by one of my students age 11.


Replies:
Yes, you do see the Earth spinning from the moon. When someone in Peoria looks up and sees the moon, someone on the moon sees the part of the Earth that has Peoria on it: North America. When someone in Hong Kong looks up and sees the moon, someone on the moon sees China. This happens once every day. The Earth spins very close to once a day for someone on the moon. Because the moon orbits the Earth once every 28 days, there is a slight adjustment. I do not know exactly how much.

Ken Mellendorf
Math, Science, Engineering
Illinois Central College


Well, yes. The earth turns 28 times faster than the moon orbits. Earth turns 15 degrees per hour, so you would have to sit and watch for a while to notice.

With a telescope you could probably see large islands disappear around the earth's limb in a few minutes, at speeds similar to the setting of the sun. Come to think of it, it would be more noticeable if the moon was over the day/night line, and then land masses would be clearly visible as they slowly sailed one by one into shadow. Could be kind of mesmerizing on clear days, with a patient mood or a high-magnification telescope. That pace is about 1000 miles per hour, you know, or 17 miles in a minute.

Jim Swenson



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