Timeline for A plausible explanation for the "ansible?" - FTL communications
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
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| Jul 29, 2020 at 19:53 | comment | added | Ross Presser | @JamesMcLellan Space expands for reasons other than gravity. There's what they're now (again) calling the cosmological constant, also called dark energy, which is causing the universe to accelerate its expansion as time goes on. There are parts of space that are "receding" from us faster than light. (They're not actually undergoing motion of this kind; instead, space between us and them is being stretched, as it is everywhere.) | |
| Jul 29, 2020 at 17:54 | comment | added | James McLellan | @RossPresser, here's Mr. White's paper - ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015936.pdf . The part I interpreted as an assumption is on page 2, second paragraph after the heading "Alcubierre Metric". Re-printing the part I believe to be relevant : "Since the expansion and contraction of space does not have a speed limit, Alcubierre developed a model (metric) within the domain of general relativity that uses this physics loop hole". Maybe I misunderstood, but I took "the expansion and contraction of space" to be the speed of gravity. | |
| Jul 29, 2020 at 17:52 | comment | added | StephenS | My understanding of an Alcubierre drive is that it moves (a bubble of) space itself faster than c, so the ship itself isn’t moving through space FTL, and speed of gravity is irrelevant. | |
| Jul 29, 2020 at 15:21 | comment | added | James McLellan | And doesn't invalidate, by the way. Still a great way to get to c. | |
| Jul 29, 2020 at 15:14 | comment | added | James McLellan | Sure, but it'll take a bit to dig up. There's a line in either Mr. White or Mr. Alcubierre's paper that I interpreted was an assumption in their work. | |
| Jul 29, 2020 at 13:46 | comment | added | Ross Presser | Can you back up your statement that speedOfGravity=c invalidates Alcubierre drives? I can't see anything in wikipedia connecting those two, and the accepted answer to this question disagrees. | |
| Jul 29, 2020 at 13:08 | comment | added | James McLellan | I could be wrong. If there's something specific, would be happy to look at it more. | |
| Jul 29, 2020 at 12:25 | comment | added | RBarryYoung | Hmm, there seem to be a number of misinterpretations and/or misunderstandings here. Could just be me I guess... | |
| Jul 29, 2020 at 1:23 | comment | added | MajorTom | James, thanks for taking the time to do this. It's really helpful to consider all these. Much appreciated. | |
| Jul 28, 2020 at 23:22 | history | edited | James McLellan | CC BY-SA 4.0 |
added 948 characters in body
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| Jul 28, 2020 at 23:11 | history | answered | James McLellan | CC BY-SA 4.0 |