Relative Motion on Face of EarthDate: 05/06/2007 at 05:18:18 From: Kaitlyn Subject: (no subject) If I am traveling at the same rate of speed that the earth is moving in the opposite direction then would it look like I was not moving looking at the earth from space? I am nine years old and in the third grade. I have looked on the NASA site and can't find it. I have also tried to make a model but can't get the two speeds to be the same. Date: 05/07/2007 at 09:12:09 From: Doctor Rick Subject: Re: Hi, Kaitlyn. The earth turns on its axis once a day; it turns toward the east (counterclockwise if you look from above the north pole). The idea, then, is that you walk westward along your line of latitude (that is, keeping your latitude--distance from the equator--constant). You walk at such a speed that you make it back home in one day. Picture the same sort of thing on a merry-go-round or carousel. (Don't really try it, it isn't safe!) First imagine that the merry- go-round is not moving, and you walk to the left along the edge so that you take one minute to get back where you started. Then imagine that the merry-go-round starts moving to the right, and its speed is such that it takes one minute to go around once. You repeat your walk; you get back to the horse where you started just as that horse gets back around to where *it* started. Now imagine your friend standing next to the merry-go-round, on the ground. At the beginning you are next to your friend; at the end of one time around, you are next to your friend. Where were you in between those two times? Think about it ... maybe a little model will help. By the way, though you don't need to know your speed in order to answer the question, it *is* interesting to find out. Suppose you're on the equator. How long is the equator (the circumference of the earth)? How long will the trip take? Can you convert the speed to miles per hour (or kilometers per hour)? Is "walking" a good way to describe it? Also, there are some tricky little issues if you want a full answer to your question about looking at the earth from space. It has to do with whether that observer is comparing your movement with the sun or the stars, and it has to do with two different ways a "day" can be defined. Also, even if you're not moving with respect to the earth, the earth itself is moving around the sun, so you'll move once around the sun in a year. You can't really be stationary in any real sense as long as you're on the earth. - Doctor Rick, The Math Forum http://mathforum.org/dr.math/ Date: 05/20/2007 at 03:31:30 From: Kaitlyn Subject: Thank you ((no subject)) Thank you very, very much for helping me with this problem. It has been bugging me for about a year and no one I knew could help me. |
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