No real purpose in space-time?

[mixinman7]

Yes, you are wrong. If you look at the clock on a spaceship moving near the speed of light relative to you, you will see the clock moving much slower. People on the rocket will see your clocks moving much slower. That is the essence of relativity.

This concept seems to contradict the twin paradox. If a twin leaves on a rocket and travels near the speed of light, he can come back and be much younger than his twin. So during that trip, the man in the rocket should be able to look at the twin's clock and see that the twin on Earth's clock is moving slower. The twin on Earth should be able to see the twin on the rocket's clock going faster. For this to be wrong I think you'd have to ignore the idea of seeing each other's clock simultaneously. That would be true while considering the time it takes for light to travel. But I am not referring to seeing clocks from telescopes. I mean if the two clocks are measured simultaneously, I'd think the difference should be as I described. Is there an element of backwards time-travel that I'm not getting?

 

[PAllen]

This concept seems to contradict the twin paradox. If a twin leaves on a rocket and travels near the speed of light, he can come back and be much younger than his twin. So during that trip, the man in the rocket should be able to look at the twin's clock and see that the twin on Earth's clock is moving slower. The twin on Earth should be able to see the twin on the rocket's clock going faster. For this to be wrong I think you'd have to ignore the idea of seeing each other's clock simultaneously. That would be true while considering the time it takes for light to travel. But I am not revering to seeing clocks from telescopes. I mean if the two clocks are measured simultaneously, I'd think the difference should be as I described. Is there an element of backwards time-travel that I'm not getting?

No, it does not contradict twin differential aging. As long as the rocket is moving inertially, Earth sees rocket clocks slower and vice versa. Fundamentally, the rocket comes back younger because it has not followed an inertial path between start and stop, while the Earth observer has traveled a (near) inertial path. Inertial paths between spacetime points are paths of maximum proper time (in SR; GR is more complex).

During the rocket's outbound inertial flight, it is as I said - by any point of view, each considers the others clocks slower (direct observation; compensating for doppler and light delays; whatever). Once the rocket turns, things are more complex. You can talk about visual appearance, and you can talk about several schemes for matching up simultaneity between rocket and earth. However, it is invariant that the rocket will have aged less by the time it returns.

 

[Daverz]

This concept seems to contradict the twin paradox.

At this point you are really just wasting people's time. Why not read up a bit first on special relativity? I recommend https://www.amazon.com/dp/0691141274/?tag=pfamazon01-20