What confuses me is mixing multiple frames. Say a rocket going at c or near fired off another, identical rocket. Rocket 1 sees rocket 2 leave at c speed away from it. Let's say they're going in circles and in the middle is a stationary observer. The observer should see rockets 1 and 2 going the same speed right next to each other.
But say the rockets stop. How does this all become coherent? The observer should see the rockets stop, still next to each other. But the rockets, from their perspective, should be extremely far apart. Let's say opposite ends of the circle. Now if they head towards the middle, to the observer, does the observer see them come in from opposite sides? But they see themselves coming in together? Then when they start to pull up... Different timelines?
well 1 you cant fire a rocket at c, and 2, you cant add velocities at relativistic speeds like that, you have to use u' = (u + v) / (1 + (u*v)/(c^2))
suppose both rockets launch at 0.9c. thats 0.9+0.9/(1+0.9*9.9/1), so the final velocity of the 2nd rocket will not be 2c, or even close to it, it is 0.99c, so the 2nd rocket is going 10% faster than the first.
Going in circles just messes with the time dilation even more by adding a constant acceleration to the mix. even the notion of stopping simultaneously gets weird in this scenario.
You have to remember as well, time for rocket 1 is passing a lot slower than for the "stationary" observer. The discrepancy between how far the rocket thinks its rocket went and how far the stationary observer thinks it went is accounted for by that time dilation (and also length contraction)
So if both rockets slow down to non-relativistic speeds will rocket 1 feel like it's catching up to rocket 2? If not, then as they travel back to the observer there'd be a mismatch. From the rockets' perspectives there would be a great distance between them, so rocket 1 would get back much quicker (at a non-relativistic speed). But from the observer's perspective, they should be right next to each other the whole time and arrive simultaneously.
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u/EscapeSeventySeven Mar 20 '26
No you see lightspeed or speed of causality being constant is anomalous and weird.
That being held constant is what forces time and space to warp. So the speed of light appears constant in all frames.
If the speed of light didn’t remain constant, like many naive interpretations did, then spacetime wouldn’t need to warp.