Earths rotation and special relativity

**git67** · Jul2-09, 07:12 AM

Now before you read this i would like to state that this is not for homework, and i am not very experienced in the study of physics, but i find it fascinating, and have a question i am curios about.

If according to the theory of relativity (i thinks its special relativity) mass which is traveling at a faster speed compared to slower mass, will experience time more quickly, Does that means if the rotation of earth was to increase in speed, would us humans appear to live longer to ourselves and would year we experience seem to go by faster?

**George Jones** · Jul2-09, 07:21 AM

Originally Posted by git67

Does that means if the rotation of earth was to increase in speed, would us humans appear to live longer to ourselves and would year we experience seem to go by faster?

No, unfortunately, time dilation does not work like this. We would see our own clocks tick normally, and our own bodies age at the usual rate.

**git67** · Jul2-09, 07:34 AM

so if there were 2 planets for instance, and the both originally moved that the same speed, but one planet's velocity increased, while the other planets velocity was unchanged. would the latter planet observing the higher velocity planet, find that the inhabitants lived longer in relation to how long the unchanged planets lived? (disregarding the perceived time the faster planets inhabitants experienced? (this may very well be a stupid question, but i want to understand more about relativity

**George Jones** · Jul2-09, 07:47 AM

I think you want to learn about something called "the twin paradox."

My wife is several years younger than me. If I get in a rocket and move away from and then back to the Earth at high enough speed (with respect to the Earth) for long enough, when I return, my wife will be older than me, event though I think I age normally, and my wife thinks she ages normally.

**DaleSpam** · Jul2-09, 07:52 AM

http://math.ucr.edu/home/baez/physic...n_paradox.html

**stone1** · Jul2-09, 10:41 AM

But what is the source of the aging difference? How can you say who moved? From your persepctive, your wife moved and so she should come back even younger than you? Is the acceleration/deceleration the source of the difference? You accelerated/decelerated while your wife's frame of reference is stationary.

Imagine that you both are rotating around a star but in oposite directions. While passing each other you take a glimpse and you both look equally young. The next time you pass by each other, what determines who looks younger and who looks older?

**Matterwave** · Jul2-09, 10:55 AM

The usual resolution of the Twin's paradox is to state that the "rest" frame is "preferred" since it has no acceleration; while the rocket ship's frame of reference accelerated twice. This brings you to the realm of General relativity, as special relativity is not readily equiped to deal with accelerations.

I have seen on Wikipedia a way to resolve this without resorting to the acceleration argument, but I've since forgotten. You may want to check that article out.

**DaleSpam** · Jul2-09, 11:19 AM

Originally Posted by stone1

But what is the source of the aging difference? How can you say who moved? From your persepctive, your wife moved and so she should come back even younger than you? Is the acceleration/deceleration the source of the difference? You accelerated/decelerated while your wife's frame of reference is stationary.

Imagine that you both are rotating around a star but in oposite directions. While passing each other you take a glimpse and you both look equally young. The next time you pass by each other, what determines who looks younger and who looks older?

The wife always looks younger. The laws of physics are irrelevant, this is a much more fundamental law that all husbands learn quickly.

However, if you want to change the objects of interest to clocks, then please see the FAQ I posted above. It answers all of the questions you have raised.