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Retarded Potential
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Is the "radar bubble of two events" known by some other, more conventional name?
I guess you mean the difference is that "ping set" includes cases such as the set is empty because the two events are spacelike separated?
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Is the "radar bubble of two events" known by some other, more conventional name?
That's actually pretty good, other than the obvious problem: that it was thought of by someone other than me.
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How does faster than light travel violate causality?
@liljoshu - re FTL for two planets in different phases of the same orbit around a black hole -- from their perspective they are stationary and their clocks would remain synchronized, just like in OP's question. Re-read the start of my answer: The trouble comes if the two planets are moving away from each other
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How does faster than light travel violate causality?
Since the whole planet isn't eclipsed, we do have radio signals between the two planets that obey the normal rules of relativity. If we measure your speed with respect to these normal signals, and if clocks on both planets also obey the normal rules, then my conclusion follows. (And if it the whole planet really was eclipsed, bounce off the moon or mars or something, this adds a some seconds or minutes but we're talking about 100000 years, so meh. Generally, I expect your warp drive is localized in some way, and outside this, the normal rules hold)
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How does faster than light travel violate causality?
"if I travel a continent over and aim so it doesn't intersect the ships path" ok you got me there! yes, that's true, if it happens to aim directly at your ship, fine :-) But your posterior isn't so big that it eclipses the whole planet :-)
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How does faster than light travel violate causality?
@liljoshu what about radio distance, does warp change that? for example, Earth and Tralfamadore are constantly exchanging radio signals (light speed). 200,000 years ago Earth sent a radio signal to Tralfamadore. 110,000 years ago liljoshu left Earth via 10-times-warp to Tralfamadore. Today Earth gets a radio signal back saying that liljoshu just arrived on Tralfamadore, at the same times as the radio signal Earth sent 200,000 years ago. As measured by Earth, liljoshu travelled at 10 times the speed of radio (light).
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