Who Ages Faster in the Twin Paradox?

[Dale]

Thanks. How is it that the law of physics is the same in every FOR when in the spacecraft FOR the astronaught clearly is not experiencing the same law of physics behaviour as that being experienced in the Earth FOR?

In the spaceships FOR clocks that move fast time dilate also. The law is the same in all inertial frames.

 

[GrammawSally]

How is it that the law of physics is the same in every FOR when in the spacecraft FOR the astronaught clearly is not experiencing the same law of physics behaviour as that being experienced in the Earth FOR?

They both use the same laws of physics. But the results they get from those laws depend on whether or not they are accelerating. The person back home never accelerates, but the astronaut does accelerate, at the turnaround.

Anytime the spacecraft is traveling at a constant velocity with respect to the inertial person back home, the astronaut will say that the person back home is aging more slowly than she is. But while the astronaut is reversing course at the turnaround (which requires her to accelerate), she will say that the person back home is aging much faster than she is.

 

[MikeLizzi]

They both use the same laws of physics. But the results they get from those laws depend on whether or not they are accelerating. The person back home never accelerates, but the astronaut does accelerate, at the turnaround.

Anytime the spacecraft is traveling at a constant velocity with respect to the inertial person back home, the astronaut will say that the person back home is aging more slowly than she is. But while the astronaut is reversing course at the turnaround (which requires her to accelerate), she will say that the person back home is aging much faster than she is.

Well said, GrammawSally.

 

[Dale]

Would it be fair to say that during a journey at the the near speed of light a second would still be a second but it would take longer to pass due to time dialation?

There is a way that statement could be interpreted to make it correct, so I would say "yes", though I am not sure that you understand yet.

Let's say you have a spaceship with a lab onboard that has an array of different science experiments, each designed to measure one second using a different physical principle, and an atomic clock. In addition, there is an array of synchronized atomic clocks. The ship is traveling at .6 c relative to the array of clocks, and begins all of the experiments as it passes a clock. All of the physics experiments end at the same time, just as the spaceship passes the synchronized clock .75 light seconds away, which reads 1.25 s.