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

In fact the paradox is that to each of the twins, time runs slower for the other one. How can time be going slower for each of them at the same time? The paradox doesn't require a resolution because they are moving apart in space, and information travel cannot exceed the speed of light. But to meet again, one of them (namely the one in the rocket ship) must stop, turn around and accelerate the other way. This is the difference between what the twins experience that determines who actually ages the most when they finally meet at the same point in space-time.

Answer 2

The difference is that the twin in the rocket experiences acceleration, the one on earth does not. Acceleration is the same as gravity--it really slows time. While the clock on the spaceship registers 1 year, the clock on Earth registers 5 years. You can actually measure this just by taking an atomic clock up a mountain (where gravity is less) for a few days and then comparing it with one left at the bottom. The clock that went up the mountain will be fast in relation to the other.

Answer 3

No.



In the twin PARADOX, both end up aging more than the other (that is why it is a paradox) because the paradox exists only if you restrict yourself to Special Relativity (inertial frames of reference). Each one appears to the other as moving fast (therefore as having a slower time flow).



The paradox is solved when you go beyond and apply General Relativity (which includes Special Relativity + accelerating frames of reference) to include the stopping and turning around of the twin who is traveling. It is in this period of this travel (the NON-inertial portion) that the real difference occurs, and he comes back having aged less than the one who stayed behind.