Given that the speed of light is the upper limit for changes to propagate through the universe; if you had a four light-year long indestructible rod and you move one end of the rod how long until the other end moves?
you’re right, I meant 4 years as aboundary even if that’s actually high.
Since it’s a hypothetical material we don’t know what max speed information can travel through it and the actual answer would be related to that, so a lower boundary at 4 years anyway.
If the material was truly somehow magically incompressible then I expect we would see some kind of time dilation so that the information could move at the right speed without deforming the rod. It would still take at minimum 4 years.
It depends. The light is definitely moving at c, no matter who checks and from everyone’s perspective, but as a consequence of that the answers to those other questions change depending on how you measure. The coordinate system (technically the “reference frame”) you choose changes the answer. Even more, time isn’t the same for each frame, so you even have to specify for whom it has been 1 hour.
Given that the speed of light is the upper limit for changes to propagate through the universe; if you had a four light-year long indestructible rod and you move one end of the rod how long until the other end moves?
I’m not an expert, but I guess it would depend on the speed of sound in the rod.
Yes - https://www.youtube.com/watch?v=DqhXsEgLMJ0 is a nice explanation.
So about 6 terayears (1.9E+20 seconds) if it’s made from the same steel.
Instantly, unless the rod flexes
Well not above the speed of light, if I read the first sentence correct.
4 light years, the universe won’t allow anything else.
That’s distance, not time.
you’re right, I meant 4 years as aboundary even if that’s actually high.
Since it’s a hypothetical material we don’t know what max speed information can travel through it and the actual answer would be related to that, so a lower boundary at 4 years anyway.
If the material was truly somehow magically incompressible then I expect we would see some kind of time dilation so that the information could move at the right speed without deforming the rod. It would still take at minimum 4 years.
This crashes the simulation.
42
Somewhat related: let’s say you’re moving at 80% the speed of light away from earth. Then you turn on a flashlight and point it away from earth.
c
OK, so after 1 hour:
It depends. The light is definitely moving at c, no matter who checks and from everyone’s perspective, but as a consequence of that the answers to those other questions change depending on how you measure. The coordinate system (technically the “reference frame”) you choose changes the answer. Even more, time isn’t the same for each frame, so you even have to specify for whom it has been 1 hour.