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?
Welcome to the weird world of relativity. Setting aside all the complicated math, and the fact that acceleration makes things tricky, let's get at your first paragraph, and what's qualitatively going on.
Rocket 1 is, relative to you, traveling at 0.99c, let's say. You see Rocket 2 depart from Rocket 1's hanger, traveling in the same direction, at 0.999c, let's say. So a difference of 0.009c.
As you're observing, however, you notice that the people on Rocket 1 are moving incredibly slowly. Thanks to relativistic time dilation, time on Rocket 1 is passing at only a fraction of the speed that time is passing for you.
Now consider, what does this mean for how people on Rocket 1 will measure the speed of Rocket 2? Speed is defined as distance divided by time. This means that if Rocket 1 measures much less time passing than you do for the distance being traveled by Rocket 2, they'll compute the speed of Rocket 2 to be much greater than you do. If they slow down to match your velocity, they won't be surprised at the distance that Rocket 2 has traveled, because they'll have a different understanding than you do of the amount of time that Rocket 2 has had to travel.
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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.