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Q & A: relativity and orbits

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Most recent answer: 05/22/2008
Q:
I've always been a little confused about the concept of space-time in the theory of Relativity. The way it was explained to me, gravity is a bending of space-time around mass. If that's true, would the Earth appear to rotate at a different speed to someone outside of its orbit? Since speed (or velocity) is a function of time/distance, How would that impact things like our calculations of the speed of light and the lightyear, if time isn't consistant? And finally, does that mean that some days feel longer because they ARE longer, and we just can't measure the difference without an outside point of reference? Thanks for putting this site up, I like to learn new things when I get bored, and it's been a long day... or has it?
- Justin (age 30)
Los Angeles, CA, U.S.
A:
I'm not sure I understand all your questions, but one has a clear answer.
yes, from the point of view of somebody outside the solar system (and not near another star) , the Earth's orbit seems to take a little longer than it does to us. The effect is very small. Likewise the calculation of distances depends on reference frame. Such effects become important when you compare different reference frames tied to stars near here and those billions of light years away.

Mike W.

The gravitational time shift was experimentally demonstrated in a classic experiment in 1958. See  http://en.wikipedia.org/wiki/Pound-Rebka_experiment .

LeeH

(published on 05/22/2008)

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