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Aug 8, 2022 at 17:36 history left closed in review Fred
WarpPrime
Ryan C
Original close reason(s) were not resolved
Aug 8, 2022 at 11:33 review Reopen votes
Aug 8, 2022 at 17:36
Jun 28, 2022 at 18:37 history left closed in review Starship
Glorfindel
Fred
Original close reason(s) were not resolved
Jun 28, 2022 at 8:45 review Reopen votes
Jun 28, 2022 at 18:37
May 9, 2021 at 17:05 comment added uhoh @tfb I understand; in an earlier comment above I link to a question I'd opened up in meta for this. I won't ping you further here but if you would like to say anything there in meta it will be appreciated. Thanks!
May 9, 2021 at 12:45 comment added Giovanni Just sayin' that I can't post on physics, for they require you to be fully registered (with your e mail account confirmed) to ask questions there. But a moderator can feel free to move this question there.
May 9, 2021 at 11:35 comment added user21103 @uhoh: (a) this discussion should be on meta not here (b) I didn't vote to close it until there were other votes, so I was intentionally waiting to see what people thought, (c) I think questions like this should be on-topic on Physics SE, not least because there has actually been research about this, and finally (d) The Alcubierre metric is well-known to be equivalent to a time machine. Are time machines on-topic here? Because what you are saying is 'yes, they are'. I'm not going to reply further here: I may be done with Space SE in fact.
May 9, 2021 at 11:14 comment added user21103 There's a result, which I think is this paper by Everett which is annoyingly behind a paywall where it's shown that you the Alcubierre metric admits closed timelike curves – time travel into the past in other words. This is unsurprising I think: it's really the same thing that's true for FTL travel in flat spacetime.
May 9, 2021 at 8:14 comment added PM 2Ring Here's the ArXiV version of a paper doi.org/10.1103/PhysRevD.85.064024 about the hazards of radiation from an Alcubierre warp bubble, and here's a brief synopsis on Universe Today. (FWIW, 2 of the authors were regulars on a now-defunct science forum that I used to frequent).
May 9, 2021 at 7:49 comment added uhoh @PM2Ring thanks for the clarification; I'm not sure how it could be helpful/useful taken in that way in this context, but it's good to hear that it should't be taken to mean anything about asking here.
May 9, 2021 at 7:17 comment added PM 2Ring @uhoh The main purpose of my previous comment was to point Giovanni to a fairly good collection of info about the Alcubierre drive. I wasn't implying that Alcubierre drive questions should be off topic, either here or on Physics.SE. I was simply mentioning that such questions do have a tendency to get closed on PSE.
May 9, 2021 at 6:05 history edited uhoh
edited tags
May 9, 2021 at 6:04 comment added Giovanni @uhoh So there is a tag "ftl"? I looked for the tag "faster-than-light" expecting it to be synonymous with "ftl" or vice versa. If the ftl tag exists, please create a synonymous faster-than-light tag.
May 9, 2021 at 5:47 comment added uhoh @Giovanni Just fyi I've asked in meta Closing “because this should be off topic” when it isn't. How to raise awareness that topicality of a question is not a “shoot from the hip” thing?
May 9, 2021 at 5:26 comment added uhoh @PM2Ring what does that have to do with Space SE? They're on-topic here.
May 9, 2021 at 3:56 review Reopen votes
May 9, 2021 at 11:24
May 9, 2021 at 3:39 comment added uhoh Voting to re-open as on-topic because Alcubierre drive questions have never been off-topic just because they are about theoretical faster-than-light propulsion. Let's keep the question open and see what answers can be posted, rather than insta-prevention of any community member from having an opportunity to post an answer to an on-topic question.
May 9, 2021 at 3:35 comment added uhoh @tfb basically I'm saying that we don't re-decide what's on and off-topic over and over again under each question, we first look carefully at precedent and community standards through similar questions via tagging and through meta. Let's try to keep topicality stable and make changes after deliberation, not the spontaneous and isolated personal views of a few each time. Community is what makes SE work so well, we should defer to it for policy and topicality issues.
May 9, 2021 at 3:29 comment added uhoh @tfb We have had ten questions tagged Alcubierre-drive and this is the first one that has been closed as off-topic. The community feels they are allowed here we should stick to that or move to make a change in meta and wait for community input. I've listed plenty of well-received theoretical questions so far, we can't suddenly make "theoretical" off topic, and "toys" is your disparagement of what pretty smart people think is more than that.
May 8, 2021 at 21:13 comment added PM 2Ring We have a couple of hundred posts on the Physics stack on the Alcubierre drive that you might like to browse. As you can see, such questions have a fairly high probability of getting closed. physics.stackexchange.com/search?q=alcubierre
May 8, 2021 at 15:08 comment added Giovanni Why was my question downvoted and closed, but not other questions in these tags?
May 8, 2021 at 15:07 comment added Giovanni @tfb I agree that time travel into the past can't be possible, but how's that related to a bubble flying at relativistic speeds? Afaik there is no time dilation when going at relativistic speeds in an Alcubierre bubble. Or is the bubble itself time travelling?
May 8, 2021 at 14:53 comment added user21103 The Alcubierre metric gives you time machines (ie you can travel into your own past). If that's possible then causality is pretty much dead. So people tend to assume that metrics which give rise to such things are unphysical. The Alcubierre metric is almost certainly directly unphysical since it violates energy conditions as well, but any similar metric would be considered by many people (including me) to be unphysical. We may be wrong, and causality may actually be dead.
May 8, 2021 at 14:33 history closed DrSheldon
user21103
Jörg W Mittag
Harish Chandra Rajpoot
BrendanLuke15
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May 8, 2021 at 14:17 comment added Giovanni @tfb Why aren't Alcubierre drives possible for you?
May 8, 2021 at 13:33 answer added Innovine timeline score: 3
May 8, 2021 at 12:50 comment added user21103 Further to my previous comment: I've voted to close this. I think that it's clearly not relevant to space exploration (if Alcubierre 'drives' are possible at all, they're not possible for us). It may have a home on Physics SE.
May 8, 2021 at 11:57 history edited Giovanni
edited tags
May 8, 2021 at 11:56 review Close votes
May 8, 2021 at 14:36
May 8, 2021 at 10:15 comment added user21103 I think questions about theoretical toys are probably off-topic (certainly I'd be much more worried about the time machines that pour out of the Alcubierre metric...). But there have been at least two papers about this I think.
May 8, 2021 at 8:56 comment added Giovanni I found this: gamelab.mit.edu/games/a-slower-speed-of-light It sort of answers my question. I can much recommend it.
May 8, 2021 at 8:34 history asked Giovanni CC BY-SA 4.0