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I'm aware that acceleration causes the change of reference; but, surely, it is the actual speed that causes time dilation. Consider this diagram:-[diagram=282_0]
Photons travel at c and for a photon, time is irrelevant - everything happens at once. They neither accelerate nor decelerate (OK, they do, but to all intents and purposes they don't) yet time dilation applies.
I asked a question about that a while back regarding how photons travelling line astern perceive each other.
george, the thing about the baby is, it has no way of knowing how old the other "stationary" object is, Unless they get together for tea later. So to answer your question, whoever accelerates after the baby is born will determine which frame of reference has aged more or less.
If you brought all three objects back together on earth, the time dilation would be dependent on how long they traveled away from one another and at what speed, so once they returned the object that traveled the farthest away from earth would be the youngest and the one that traveled not so far would be younger than the earthlings but not as much younger.
thebrain - I was assuming that both set out from Earth. 1 accelerated then immediately decelerated. The other accelerated, maintained speed for a while, and then decelerated. I was just wondering how time dilation would affect each of them.
They can be at the same place at the end if they make cirular trips out from Earth & then return. B's loop would obviously be much bigger than A's.
Quote from: DoctorBeaver on 13/10/2007 11:46:46They can be at the same place at the end if they make cirular trips out from Earth & then return. B's loop would obviously be much bigger than A's.But if you are travelling in a circle then you are under constant acceleration, which is very different from the inertial reference frames that special relativity addresses.