In the twin paradox why does the one on Earth always age more?

Question

In the twin paradox where one brother takes a rocket close to the speed of light and returns to earth to see that his brother has aged significantly more than him why does the reverse not happen?

What i mean is that relative to the twin on the rocket the earth is actually moving away from him at the speed of light so the clocks on earth should appear to be moving slower and then the twin on the rocket should instead age faster.

So why does it seem that relative to both observers it is always the twin on earth that seems to age more?

Answer 1

Because initially, both twins are at rest with one another and share the same inertial reference frame. However, the twin that enters the space rocket has to accelerate to approach light speed and it's during this acceleration (and later, during deceleration from light speed) that he/she is no longer in an inertial reference frame. All this time, the other twin who remains on earth remains in the same inertial reference frame. The fact that one experiences a change in his/her reference frame and the other does not accounts for the difference.

Answer 2

Twin Paradox:



In SR all motion is relative. That means that if I was "motionless" and you went by at a constant velocity that was a significant fraction of the speed of light, I would see your clock running slower AND you would see my clock running slower. ====> So, which one of us is aging slower? Paradox! The Twin Paradox is subtly different. Both twins start from the same motionless Frame of Reference. You could not use accelerometers in the above case to determine which of us was moving. But, for the twins, we could put an accelerometer with each twin. Then, we could determine which twin accelerated ===> which one is moving relative to the original FoR. The 2 FoRs are now no longer inertial, one is accelerated and the twin in the accelerated FoR is the one that ages slower.

Answer 3

You're thinking about this just a bit too hard! ;-) Let me explain . . .



The twin on the earth has been ageing at the rate called Earth Time.

The twin in space has been aging at a much slower rate, compared to Earth Time.

Hence, upon the space-traveller's return to earth, where Earth Time is the standard measure of time for both of them, it is the earth-bound twin who has gained years relative to his twin. So, the earth-bound twin is older.



HTH,

Skywave.

 

Answer 4

Watch and learn:

http://www.youtube.com/watch?v=K6iMAjfz1k8