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Alcubierre drive
- zunzun 8y agoIt would be way cool if one of these could be installed in an old VW Beetle. Totally excellent fuel economy!
- deleted 8y ago[deleted]
- BlackFly 8y agoThere was a time where relativists realized that instead of solving the Einstein equations subject to initial conditions coupled to some matter stress energy terms, they could instead fully specify what spacetime looks like, ram it through the Einstein equations and get a stress energy tensor on the right hand side. The Einstein equations became a recipe generator: if you want this spacetime, then you need this matter/energy. Unfortunately, all the interesting spacetimes (such as the Alcubierre drive) require exotic matter, matter unlike anything we have ever seen. Other spacetimes people were interested in generating were stable wormholes. If we could ever produce such matter then we could start some spacetime engineerinng. Meanwhile, we are left with these oddities. I heard that Alcubierre somewhat regrets having his name on this spacetime as he gets contacted by all kinds of Star Trek fans and other people who believe they can produce the drive. He has done all kinds of other quality research in General Relativity, but this is what he will be famous for.
- King-Aaron 8y ago> he gets contacted by all kinds of Star Trek fans and other people who believe they can produce the drive. I would genuinely love to read some of the exchanges between Alcubierre and these people.
- ailideex 8y agoWhat makes you think he engages with them?
- SiempreViernes 8y agoSome might be polite and somewhat knowledgeable (though most won't be either).
- memberZero 8y agomake it so
- thanatropism 8y agoIn the late 90s to early 2000s I was a teenager and communicated with various scientists and academics via email, some of which had something of a mentor role. By those experiences I'd say someone like Alcubierre is more likely to engage young ducklings than, say, Michio Kaku.
- light_hue_1 8y agoNo problem: https://www.youtube.com/watch?v=5q_z8BjiYng https://www.youtube.com/watch?v=5q_z8BjiYng This is one example of many. The original poster was just spreading FUD and saying nasty things about Alcubierre as a researcher. He gives talks like this all the time, he refers to his own work as a warp drive, he quotes and shows off Star Trek, etc. This isn't an issue of crazies trying to steal someone's research.
- magicalhippo 8y agoThat Michio Kaku episode[1] on Discovery where he said[2] that we might be able to harness the Casimir effect as a source of the negative energy needed for the Alcubierre drive probably didn't help. There are more realistic explanations[3] for the Casimir effect however, so no Alcubierre drive for us anytime soon. [1]: Think it was this show https://en.wikipedia.org/wiki/Sci_Fi_Science:_Physics_of_the_Impossible https://en.wikipedia.org/wiki/Sci_Fi_Science:_Physics_of_the... [2]: To be fair, Alcubierre suggested it himself first [3]: https://en.wikipedia.org/wiki/Casimir_effect#Relativistic_van_der_Waals_force https://en.wikipedia.org/wiki/Casimir_effect#Relativistic_va...
- ben_w 8y agoEven if your [3] doesn’t apply, I believe the Casimir effect doesn’t scale fast enough — even a cavity made from proton-sized parts will never exclude more vacuum energy than the mass energy of those protons: https://kitsunesoftware.wordpress.com/2017/04/20/can-a-casimir-cavity-be-used-to-construct-true-negative-mass-metamaterials/ https://kitsunesoftware.wordpress.com/2017/04/20/can-a-casim...
- EastLondonCoder 8y agoThis is very true, it’s also worth mentioning that all ways of faster than light travel means travel back in time in some reference frame which in breaks causality.
- magicalhippo 8y agoHere's a good (IMHO) video showing how this works out, by looking Minkowski diagrams for different observers. https://www.youtube.com/watch?v=HUMGc8hEkpc https://www.youtube.com/watch?v=HUMGc8hEkpc
- computerfriend 8y agoBreaking causality is allowed, though.
- garmaine 8y agoBreaking causality is allowed by the laws of physics.
- zamalek 8y agoYou don't travel faster than light with the Alcubierre Drive, you circumvent travel entirely. Spacetime does the traveling, not the ship.
- Razengan 8y ago> If we could ever produce such matter then we could start some spacetime engineering. Imagine the exotic "pollution" caused by civilizations which are advanced enough to tinker with the fabric of spacetime, but not advanced enough to understand (or care about) the long-term consequences of that tinkering. Destabilizing solar systems or even entire galaxies, maybe even violating causality.. Imagine the home (and only) planets of younger, insignificant civilizations being caught up in those cataclysms, all traces of their existence wiped from cosmic history in what might amount to the equivalent of a traffic accident or "oil spill" of a greater civilization. ..maybe that has already happened and some of the leviathanic voids we've observed were a result of that? :) [0] https://en.wikipedia.org/wiki/Void_(astronomy) https://en.wikipedia.org/wiki/Void_(astronomy)
- SiempreViernes 8y agoWell, there was that time Earth was demolished to make room for a bypass. I'm not sure I recall all the details but I think the universe ended as a convoluted consequence?
- Razengan 8y agoYep, that is exactly what I was thinking about. :)
- golergka 8y agoThat sounds like some great sci fi, actually.
- Razengan 8y agoEver since I played the awesome old RPG called Planet's Edge [0] and the better-known Star Control II, I've been taken to muse about cosmic coincidences. Popular sci-fi like Star Wars or Star Trek etc. don't really touch on those possibilities in a convincing way. As in, very few fiction truly conveys the ..indifference.. of the universe, and all the actors in it going about their own businesses and interacting only incidentally, even if to monumental consequences to each other, but without a lot of conscious intent or an overarching plan. Kind of like how most of Earth's history has played out, even if it may all seem interconnected and purposeful due to the much more relatable scales involved. [0] https://en.wikipedia.org/wiki/Planet%27s_Edge https://en.wikipedia.org/wiki/Planet%27s_Edge
- Hydraulix989 8y agoIs there nothing interesting within the constraint of a reasonable stress energy tensor?
- Eochei5h 8y agoBlack holes and possibly topological defects.
- exoesquitur 8y ago.... But you make one warp drive....
- JumpCrisscross 8y ago> all the interesting spacetimes (such as the Alcubierre drive) require exotic matter Does it have to be matter? Or could we coax the vacuum into behaving as if it were occupied by exotic matter?
- ailideex 8y agoMatter is just excitation in the vacuum. But excitation with positive energy. What is needed is excitation with negative energy.
- light_hue_1 8y ago> I heard that Alcubierre somewhat regrets having his name on this spacetime as he gets contacted by all kinds of Star Trek fans and other people who believe they can produce the drive. He has done all kinds of other quality research in General Relativity, but this is what he will be famous for. This is untrue, it's really offensive to a person that's dedicated years of his life to this research, and it set a terrible tone for the rest of the comments. He gives talks all the time to groups that are interested in developing a "warp drive". He puts up photos of Star Trek in his talks! He even refers to his own work as potentially developing a "warp drive". Look at one of his recent talks https://www.youtube.com/watch?v=5q_z8BjiYng https://www.youtube.com/watch?v=5q_z8BjiYng and please stop spreading negative rumors about scientists.
- warent 8y agoAs an aside, I'm loving this talk (the YouTube video). Thank you for sharing
- geraltofrivia 8y agoIssac arthur has a fascinating video on the topic, that I recommend to anyone who's interested in the idea: https://youtu.be/yCCsmxGjEV0 https://youtu.be/yCCsmxGjEV0
- russdill 8y agoHe ties it in well with his Fermi paradox videos. If such a thing is possible, it makes the stakes of the Fermi paradox much higher. We aren't just wondering why we don't see other intelligent life in our galaxy, but why we don't see it in a much larger region of the Universe.
- paulhallett 8y agoThe frame shift drive in the ELITE video game series is based on this technology: https://www.reddit.com/r/EliteDangerous/comments/2nqtzp/frame_shift_drive_science/ https://www.reddit.com/r/EliteDangerous/comments/2nqtzp/fram...
- no1youknowz 8y agoAsteronX is an awesome channel and goes into the mechanics of space travel [0] and then two videos on the Alcubierre-Froning Warp drive [1], [2]. [0]: https://www.youtube.com/channel/UC2kkCGRqZWaSIK3BmLC8vaw/videos https://www.youtube.com/channel/UC2kkCGRqZWaSIK3BmLC8vaw/vid... [1]: https://www.youtube.com/watch?v=n38aP2tROBo https://www.youtube.com/watch?v=n38aP2tROBo [2]: https://www.youtube.com/watch?v=M3fw2wQlWL4 https://www.youtube.com/watch?v=M3fw2wQlWL4
- nabla9 8y agoTemplate for discussion: A: It requires hypothetical exotic matter. It's just theoretical thought experiment. B: counterargument: The existence of exotic matter is not theoretically ruled out, so it could be real. A: That's not a good argument. Something completely hypothetical invented so that it allows what you want to happen not ruled out is not good argument for relevance. B: platitude counterargument: "If an elderly but distinguished scientist says that something is possible, he is almost certainly right; but if he says that it is impossible, he is very probably wrong." - Arthur C. Clarke. MOT.
- bvinc 8y agoI'm not a physicist, but my understanding is that exotic matter isn't strictly required. They say that because what's needed is a sort of negative energy/mass to cause an anti-gravity effect. But even that isn't accurate. What's really required is a lower energy density than a vacuum. This can be achieved in some cases, for example, in the casimir effect. When you look at it that way, it opens up some possibility, that we could achieve this in some sort if fashion, at least on a small scale, right? Can someone more knowledgeable than me weigh in on this?
- trhway 8y agothe best counterargument for me is that remote galaxies run away from us with the speeds larger than c. So space expansion and the speed faster than c as a result is possible. Without exotic matter, etc. Now there is just an engineering task of implementing it as a practical space ship drive. The arguments against FTL are based on fixed spacetime frames of references. Which is obviously not-applicable to the situation where the spacetime is what you actively manipulate. Spacetime manipulating approaches don't violate SR as nothing is moving faster than c wrt. local space. The same like with those remote galaxies - while running faster than c from us they don't move faster than c wrt. their local space.
- raattgift 8y ago> space expansion and the speed faster than c as a result is possible. Without exotic matter, etc. Except that in order to get the observables right, dark energy is required to keep the galaxy clusters running away from each other faster over time. It's a heavy price that no physical cosmologist is really happy about, but the concordance cosmology gets its name from how it is explicitly constructed to match ("concord with") observation (and it is consequently updated from time to time). It is not really surprising that some energy is required to keep the warp bubble from dissipating away from its compact region of spacetime, particularly since the Alcubierre model is a vacuum spacetime, so there's no mass in the middle to keep the bubble local to it (or source it, or however you want to look at it). He says so at the end of his paper[1]. It's important to remember that there is no observational evidence supporting Alcubierre's metric; it concords with nothing. However, one can still attempt to answer the questions he himself raised, and Lobo & Visser do just that in their 2004 paper[2], where they note that the geometry of the Alcubierre metric requires an even-more-unusual-than-dark-energy stabilizing term even at arbitrarily low warp-bubble velocities. - -- [1] https://doi.org/10.1088/0264-9381/11/5/001 https://doi.org/10.1088/0264-9381/11/5/001 https://arxiv.org/abs/gr-qc/0009013 https://arxiv.org/abs/gr-qc/0009013 (short, not especially difficult, fewer than 20 equations, 4 refs) See the text bracketing eqns (18) & (19) [2] https://doi.org/10.1088/0264-9381/21/24/011 https://doi.org/10.1088/0264-9381/21/24/011 https://arxiv.org/abs/gr-qc/0406083 https://arxiv.org/abs/gr-qc/0406083 (twice as long, but mostly developed through more than 120 equations, 38 refs incl. [1])
- jlebrech 8y agohow about we just figure out how to get as close as possible to 1C?
- Xophmeister 8y agoWe already know how to get arbitrarily close to 1C: just keep adding energy to the system to produce enough thrust to overcome the additional mass of said energy's source and the relative mass increase from getting closer to 1C. It's just not practical and the laws of physics forbid it from ever being practical.
- jlebrech 8y agobut if we keep trying there should be a spacefaring equivalent of Moores law? what if instead of formula 1 we had races in orbit? this would push the boat out.
- 3rdAccount 8y agoNo. Moore's law is about making things smaller for speedups. We can't shrink Relativistic Physics like that to lower the energy required to reach 1c (infinite). Of course, it is possible that there is a better standard model of physics which does a better job of explaining things and which does say we can do so. Another space race or space F1 would definitely make our engineering better and more reliable, but at massive cost and we still won't get FTL.
- avian 8y agoI doubt any metric in Formula 1 doubles every 2 years. To get something like Moore’s law you need a breakthrough that opens up possibilities for many orders of magnitude in improvements. Baring new physics there’s just nothing like that available for rocketry.
- logfromblammo 8y agoNearly all racing formats have banned certain technologies. For instance, swimming banned LZR Racer swimsuits as "technology doping". Formula 1 has banned a variety of technologies, some just for increasing risk to spectators. America's Cup banned pedal power and cyborgs. Most human-powered races ban performance enhancing drugs. I could easily see space racing banning negative mass.
- pcnix 8y agoFor anyone interested in fiction based on ideas like this, check out the Three Body Problem series. I'll avoid talking about it further to keep from spoiling it.
- deepnotderp 8y agoDidn't they propose to elide the use of exotic matter with a Casimir vacuum. EDIT: it says that in the wikipedia article too
- yannk 8y agoIt reminds me of Hyperion's Cantos' "Hawking drive"