[HN Gopher] Warp drive's best hope dies, as antimatter falls down ___________________________________________________________________ Warp drive's best hope dies, as antimatter falls down Author : WithinReason Score : 134 points Date : 2023-10-09 10:52 UTC (12 hours ago) (HTM) web link (bigthink.com) (TXT) w3m dump (bigthink.com) | jedberg wrote: | It's ok, we still have 40 more years to figure it out. | nv2156 wrote: | Yeah once Dr Cochrane starts working on it :). | jedberg wrote: | Give him a break, he isn't even born yet! | WendyTheWillow wrote: | Maybe we should start naming every single person born as of | now-ish, Zefram Cochrane, just to be safe... | qingcharles wrote: | I tried with Beastmaster and Swampmonster with First Wife, | but I'm not Elon Musk so it didn't fly. I might be able to | sell Zefram Cochrane, though. Do you think it'll matter if | Cochrane is his middle name? :D | ruined wrote: | that's quite optimistic. i'd give us fifteen tops | stevula wrote: | It's a reference to the year warp drive will be invented by | Zefram Cochrane in the Star Trek universe. | OhNoNotAgain_99 wrote: | [dead] | davedx wrote: | The whole article feels like a strawman, I wasn't aware anyone | was presuming antimatter could lead to the negative energy | required for the warp drive metrics... | | Antimatter is not negative mass or energy. The experiment | verifying it falls down wasn't surprising | andrewflnr wrote: | The author addresses this (in a very condescending way) in the | last couple paragraphs. But yes, I tend to agree with you. | SkyMarshal wrote: | _> If any sort of mechanism could exist for circumventing the | limitations of conventional travel through spacetime -- | limitations set by the speed of light -- it must involve | leveraging the curvature of spacetime to create such a "short- | cut" between two otherwise disconnected points. Perhaps the most | famous instance in all of fiction to leverage this was the idea | of "warp drive" as developed by the Star Trek franchise._ | | Did Star Trek actually originate the warp drive idea? I always | assumed some scientist somewhere originated it first, then the ST | writers picked up on it and used it in their world-building. But | kind of mind-blowing if it was the ST writers who originally | conceived it. | | _> By expending a vast amount of energy, the idea was that space | could be severely curved, and in some sense, compressed. As the | space ship moved through the compressed space, it would take this | long-sought-after short-cut, enabling very rapid travel over | great distances, without causing the outside Universe to age | rapidly relative to the crew._ | | There are conflicting conceptions of warp drive accelerating time | outside the warp bubble (or decelerating it inside the bubble). | Star Trek's warp drives obviously don't accelerate external time | (or slow internal time). But in Cixin Lui's Three Body Series, | curvature propulsion (aka warp drive) does slow internal warp | bubble time. Which is correct? | Agathos wrote: | "Warp Drive" dates back to 1947 (John Barret, "Stellar | Snowball") according to sfdictionary.com (a resource I love for | this kind of question). | | Other phrases like "Space Warp" go back even further (Nat | Schachner, "The Son of Redmask", 1935). | johnchristopher wrote: | Side note: re-watched ST2 and 3 recently and switched to french | audio for a bit for giggles and nostalgia: warp speed got | translated to "exponential hyper-atomic". | phkahler wrote: | We still don't know if regular matter is gravitationally repelled | by antimatter. If so, we'd have violation of conservation of | momentum and some interesting things might be possible. But I'm | not holding my breath ;-) | data_monkey wrote: | I don't understand this result. How would this experiment be able | to detect the "antigravity" of antimatter? If the Earth is | curving space time in one direction and then antimatter is | curving space time in the opposite direction, would not relative | impact of the antimatter be so negligible to be undetectable? We | are talking about the ability to "unbend" space time of what a | particle or two relative to the mass of the earth? So what if it | falls, that just means its barely unbending space time. | | To use an analogy, Let's say I am on the Amazon river (fastest | river according to google). You want to detect which way I was | swimming. Would you even be able to detect the marginal effects | of me swimming upstream relative to the massively more impactful | force from the river? | | I am sure the problem here is me, so if someone can correct my | thinking. | dmurray wrote: | > To use an analogy, Let's say I am on the Amazon river | (fastest river according to google). You want to detect which | way I was swimming. Would you even be able to detect the | marginal effects of me swimming upstream relative to the | massively more impactful force from the river? | | Definitely yes! If you're even a reasonably competent swimmer | you should be able to outswim the Amazon and make headway | upstream at most points. | | I'm not sure what this says about your analogy, but I would | think the measurement devices are millions of times more | sensitive than needed to detect which way you were swimming. | mnw21cam wrote: | You're making a very interesting distinction between the | experimental result, which is that antimatter _follows_ the | same space-time curve as normal matter, and the dashed hope of | warp drives, which is that antimatter _causes_ the same space- | time curve as normal matter. | | However, if antimatter were to create a negative curvature but | follow positive curvature, then you would be able to put a lump | of normal matter next to a lump of antimatter, connect the two | together, and the whole mechanism would spontaneously | accelerate forever, breaking the laws of conservation of energy | and momentum. For that reason, I think this experiment also | gives us high confidence that antimatter causes exactly the | same space-time curvature as normal matter, even though we | haven't gathered enough antimatter to see it creating a normal | space-time curvature. In essence, gravity is _symmetrical_. | stromgo wrote: | Maybe it helps to consider all 4 possibilities for the sign | of the gravitational mass of antimatter, and the sign of the | inertial mass of antimatter? | | (-,-): antimatter would fall down, but we could break | conservation laws with a mechanism. | | (+,-): antimatter would fall up, but we could break | conservation laws with a mechanism using electrically charged | particles. | | (-,+): antimatter would fall up, but ruled out by the | experiment. | | So what remains is (+,+)? | [deleted] | elil17 wrote: | To my understanding, the researchers released antimatter | particles with detector plates above and below them. The | particles started out traveling in random directions. Some of | the particles hit the top, some hit the bottom. They saw that | more particles hit the bottom than the top. | | If the particles had "anti-gravity", they'd be repulsed by the | large mass of the earth (instead of attracted), and you'd have | expected more to hit the top plate than the bottom plate. | | The researchers also added a magnet to the top designed to | cancel out the downward force from gravity, and they hit the | top and bottom plate at even rates. | pvaldes wrote: | Hum, How can they be sure that what is hitting the plate is | still antimatter? (Or only antimatter?) | ben_w wrote: | Positrons react with electrons to produce a distinctive | pair of 511 keV photons travelling in opposite directions | in the frame of reference of their collision. | | There's also a much more complex mess that happens when | protons react with antiprotons. | mperham wrote: | Quanta and BigThink are such great sites, pumping out high | quality science journalism. | rilindo wrote: | BigThink, ironically, is sponsored by the Charles Koch | Foundation. | WendyTheWillow wrote: | Can you cite this? All I see is that BigThink is owned by | FreeThink [0], and FreeThink appears funded by Bedrock | Capital and MaC Venture Capital [1], neither of which I can | tell are associated with the Charles Koch Foundation [2][3]. | | That said, I've spent ~5 minutes on this, so I certainly | missed something. | | [0] https://bigthink.com/our-mission/ | | [1] https://www.crunchbase.com/organization/freethink- | media/comp... | | [2] https://www.linkedin.com/company/bedrockcap/ | | [3] https://www.linkedin.com/company/mac-venture-capital/ | esc861 wrote: | I was under the impression that there were potential positive- | energy solutions to this problem that don't require antimatter: | https://iopscience.iop.org/article/10.1088/1361-6382/abe692 | captn3m0 wrote: | We've lost the "best hope", not all hope. | pnpnp wrote: | Was this really its best hope? I still have my fingers crossed | for an Alcubierre drive using antimatter as an energy source. | | Hasn't work been done in this area recently? I remember seeing an | article saying it might technically be possible with a | hilariously large energy source, but I don't know if that has | been disproven. | aardvark179 wrote: | So what's going to provide your negative energy density, given | it isn't going to be antimatter now, and that was our best | candidate? | gs17 wrote: | >Also dying with this measurement is another sci-fi hope: | artificial gravity that works without rotation or acceleration. | If antimatter truly anti-gravitated, then simply by building a | spacecraft's floor out of normal matter and its ceiling out of | antimatter, we could create a spacecraft that had its own built- | in, automatic system for artificial gravity. | | I've never heard this idea, but that sounds hilariously | dangerous. | thereddaikon wrote: | I have never heard of antimatter being used in that way, even | in the most off the wall, science illiterate speculation. | Usually its as a power source. | andrewflnr wrote: | Yeah, because the idea of antimatter being anti-gravitational | is so obscure and silly that not even scifi authors use it. | db48x wrote: | The idea was mostly limited to really bad science fiction, the | kind that is really a fantasy with science-fictional set | dressing. | LeifCarrotson wrote: | Doesn't that proposal merely ~halve the amount of mass | required? | | I'm in an office right now that has a ceiling made out of | normal matter (gypsum, fiberglass, steel, and tar, probably a | couple thousand kg overhead) and a floor also made out of | normal matter (carpet, concrete, iron, silicon, oxygen, and a | bunch of other stuff adding up to 6x10^24 kg), which generates | artificial gravity at 1g. It happens to be rotating at 1/1440 | RPM, but that's only a 0.2% reduction in the acceleration. | | Sure, if antimatter caused anti-gravitational forces, you could | have achieved the same gravitational acceleration I experience | in my office using one 3x10^24 kg sphere of antimatter overhead | and one 3x10^24 kg sphere of matter beneath, but that's still | not a Starship Enterprise, much less an X-wing, with artificial | gravity generators. You're still stuck at: F | = G x m_matter / r^2 + G x m_antimatter / r^2 F = | 4 x pi / 3 x G x density x radius_matter + 4 x pi / 3 x G x | density x radius_antimatter | | with planet-sized masses and radii for both. | | And I'm not sure that "hilariously" is a sufficient modifier | for the danger level when standing in a 3m gap between planet- | sized spheres of matter and antimatter. | izzydata wrote: | What about building a circular ship around a micro black hole? | Or is that just real gravity and not anti-gravity? | Cthulhu_ wrote: | Note: armchair reply, I don't know enough astro whatnots to | substantiate this take: | | That implies that you can actually move the black hole; a | black hole producing 1G requires it to be as heavy (or, to | have as much attraction) as the earth itself. It would be a | lot more compact - a black hole as heavy as the earth is | about the size of a ping pong ball - but if my intuition is | correct, would require as much force to move as it would to | move the earth. | db48x wrote: | Yep, F=ma. For a given force, if mass is big then the | acceleration must be small. | | Also, I feel compelled to mention that to get an Earth-like | gravitational field near the event horizon of a non- | spinning black hole, it needs to mass more than the whole | galaxy. It would be about a light-year across, iirc, and if | you built a shell around it (which would not be easy) then | the surface area would be so large as to beggar | description. | | Small black holes are not very earth-like because of the | extreme tidal forces. Trying to stand on that ping-pong | ball would be extremely uncomfortable. | User23 wrote: | If it's an antimatter black hole you can dump normal | matter into it to release energy, assuming some way | exists to turn that into useful acceleration. | nyssos wrote: | An "antimatter black hole" is just a black hole. There | might still be something behind the event horizon to | annihilate with, there might not, the question might be | meaningless, but in any case you're not getting anything | back out again. | User23 wrote: | Don't have to get anything out just need to accelerate | the singularity. | ben_w wrote: | It doesn't, at least not within currently understood | physics: | | https://www.youtube.com/watch?v=cFslUSyfZPc | | You'll push the black hole with precisely the same | momentum (in the opposite direction) as you yourself got | from whatever device was pushing the matter towards the | black hole. | aetherson wrote: | And hilariously useless even if you wave away the costs and | catastrophic dangers. Yes, you can have a floor of normal | matter and a ceiling of antimatter and produce... like... maybe | 0.00001 m/s^2 of gravity? | thsksbd wrote: | And ludicrously energetically expensive. | | But that's science proposal writing, isn't it? Propose | something that would be ludicrous even if it were physical. | mr_mitm wrote: | Ludicrous barely begins to describe the idea. It would have | to be a mass on the order of magnitude of a moon that you | would have to a) create and b) carry with you so that you | would feel some gravity. Why not just build a rotating ring | instead? No one in scifi was even entertaining this idea | afaik. | thsksbd wrote: | "It would have to be a mass on the order of magnitude of a | moon" | | Here I am overcomplicating things in terms of E=mc2, and | you come and point out the obvious. | Izkata wrote: | > No one in scifi was even entertaining this idea afaik. | | Yeah, this is the first I've heard of it too. If it's not | rotation it's usually left unexplained, and when it's not | it's usually something along the lines of an artificial | gravity generator that pulls things towards it, like in | Star Trek the floors contain "gravity plating" that does | that on a small scale. | mr_mitm wrote: | It's never wrong to confirm by experiment, but there was never | really any doubt among professional physicists that antimatter | falls down. Similar doubts are expressed about the feasibility of | the warp drive by Alcubierre himself: | https://twitter.com/malcubierre/status/362011821277839360 | OhNoNotAgain_99 wrote: | [dead] | marcosdumay wrote: | I don't think anybody expects a wrap driver to be possible. | It's just one of those odd things where the math says | something, and it's well work looking at just in case. (Just | like negative mass matter is something that nobody expects to | exist, but likes to appear on equations here and there.) | | That said, I don't follow it closely, but didn't somebody | recently worked out one that works without negative mass | matter? | distract8901 wrote: | >That said, I don't follow it closely, but didn't somebody | recently worked out one that works without negative mass | matter? | | Yes. There was recently a few papers published showing that a | static warp field is mathematically possible without negative | energy. However, the field doesn't move or impart | acceleration on its own. The best you can do is drag the warp | field behind your ship with normal thrusters. Such a field | seems to be pretty useless right now, but maybe that research | will lead to something else in a few years | stouset wrote: | What exactly _is_ this "warp field", then? | nathan_compton wrote: | spacetime. | lawlessone wrote: | >The best you can do is drag the warp field behind your | ship with normal thrusters. Ok we can build a warp | trebuchet. | distract8901 wrote: | The static warp field doesn't allow you to go faster than | light because it doesn't move relative to the generator. | You can drag the field around at sublight speeds but | that's about it. | | Though IIRC they played around with some different | geometries that did move, but the energy required was | many times more than the entire universe contains. | I_Am_Nous wrote: | Perhaps not useless, but definitely not as convenient as we | hope warp technology will be someday. Could such a device | be used as a way to improve thruster efficiency? If you can | drag a large enough warp bubble with conventional | thrusters, and it "slopes" space in front of you, could it | make moving in the direction of the slope easier so you use | less fuel? | delecti wrote: | It always seemed like a reasonable, but still big, assumption | that antimatter behaved the same way under gravity. Anti- | particles have opposite charge, so maybe it could have made | sense that they have opposite "gravitational charge"? But also | gravity doesn't _have_ "charge". | | So yeah, agreed. A good thing to confirm, even if (especially | if) they expected the result to be unexciting. | NoGravitas wrote: | Even among people who hold out hope that a warp drive is | physically possible (as opposed to merely mathematically | possible), I don't think _anyone_ ever suggested that | antimatter was a candidate for the negative mass required by | the equations. It 's always been some kind of unobtainium. | mst wrote: | Agreed, though also I really appreciate this sort of "obvious" | experiment, because the incentives really aren't set up to | encourage it and we've been surprised often enough over the | centuries that Actually Double Checking is probably something | we should do more of. | | (there's a parallel here to 'more negative results' and 'more | replications') | mr_mitm wrote: | Yes, nobody expected to find a positive cosmological constant | either. Well except Steven Weinberg kinda. | netbioserror wrote: | Why would anti-matter be theorized to produce anti-gravity? I | thought the "anti" part only amounted to charge or spin, with | mass still being positive? | Khoth wrote: | I don't think anyone really expected antimatter to produce | antigravity, but it had never been tested before so it was | worth doing the experiment. | raattgift wrote: | One of the questions in physical cosmology is, "why is there so | little antimatter/matter mixing in the cosmos?". We can measure | the mixing by looking for the annihilation spectrum (e.g. e+ e- | -> 511 keV/c^2, which for distant extragalactic sources should | redshift with the expansion of space). We can produce lots of | e+ (positrons) and other antimatter here in laboratories, and | so have a fair chunk of the total annihilation spectrum. We | also have the spectra of lots and lots of galactic objects | (stars, neutron stars, and so forth) and spectra from | extragalactic events large (neutral hydrogen clouds) to small | (supernovae). There is essentially no sign of known matter- | antimatter interaction. | | Our galaxy and other members of its cluster are, to high | confidence, made essentially entirely of matter. | | We have not yet totally precluded distant isolated galaxy | clusters made essentially of antimatter, but the cosmic ray | spectrum (we see lots of particles that originate at | cosmological distances) puts increasingly strong constraints on | the distribution and density of such galaxies: there aren't | many in total, there's no dense blob of them. The oldest | galaxies that we can obtain spectra are also closer together, | and each non-observation of annihilation spectral lines puts | ever-tighter constraints on other old galaxies' | antimatter/matter mix. It is fairly safe to bet that there is | simply no significant blob of antimatter in the observable | universe, and that what antimatter there is comes from nuclear | decays and high-energy astrophysical processes, and all of this | antimatter quickly annihilates spatially near where it's | produced. | | However, that raises a trio of questions. (1) Did some process | strongly disfavour the production of antimatter in the early | universe, when hydrogen and helium was being produced in | abundance? (2) if (1) is true, what is the nature of that | process, and how could we see it experimentally? (3) if (1) is | not true, where did all the antimatter go? There is an | inversion of (3) as well: why didn't the disappearing | antimatter take all the matter with it too? | | The above is the essence of "the missing antimatter problem" or | "the matter-antimatter asymmetry problem" or "baryon asymmetry" | <https://en.wikipedia.org/wiki/Baryon_asymmetry> (that last | name is for technical reasons, including that there are lots of | antineutrinos, anti-photons (which are just photons), and | (somewhat complicatedly) anti-gluons and antiquarks [endnote 1] | in our universe) and there is a substantial academic literature | by experimentalists and theorists. | | A family of that literature explores the idea of _segregation_ | : matter and antimatter had similar abundances but were driven | apart by some process in the early universe. The result is that | there will be large (observable-universe-size-or-bigger) | regions dominated by antimatter, and large regions (like ours) | dominated by matter. But what is the nature of the process? | | A subfamily exploring that last question considers the | possibility that the segregating interaction is gravitational; | a sub-sub-family considers that a change of sign of quantum | spin can generate a gravitational difference. One approach to | this is to treat quantum spin as a generator of the spin tensor | in a modification of General Relativity in which the spin | tensor generates the torsion tensor. In General Relativity | there is no spacetime torsion at all, so in "semiclassical | gravity" where one adds quantum fields to General Relativity | (e.g. as in Stephen Hawking's famous 1974 "Black hole | explosions?") matter and antimatter gravitate identically. | Introducing non-vanishing spacetime torsion can change the | nature of black holes enough that black hole evaporation could | be very different. And if one couples particle spin to torsion, | one could distinguish a black hole created by significant | antimatter from a black hole created by practically no | antimatter, and we would expect that to show up in the spectra | of active galactic nuclei (generated by supermassive black | holes) and in the gravitational wave detections of black hole | mergers and black hole-neutron star collsions. | | Apart from the lack of observational support (which one could | sidestep by saying that there is basically no antimatter | available to large black holes because it was all chased out of | the observable universe by spacetime torsion effects), this | quantum spin = spacetime torsion approach runs into a number of | theoretical problems. The anti-hydrogen experiment that's the | subject here adds a further problem that would need solving. | Why would antimatter-matter gravitation today work differently | from antimatter-matter gravitation in the early universe? If | they work the same, then this experiment makes it unlikely that | gravitational repulsin from torsion could solve the missing | antimatter problem via _early segregation_. | | This antihydrogen result also imperils proposals for theories | of quantum gravity wherein quantum spin (other than that of the | graviton or its string equivalent) is gravitationally relevant | (but not necessarily arising in that family of string theories | especially to solve the missing antimatter problem, i.e., "our | theory has a gravitational spin-antispin term in the action | which we don't mind because maybe it's too small to matter or | maybe if it's big at high energies (like in the hot dense early | universe) it can solve a big problem like the missing | antimatter problem", essentially). | | Finally, wikipedia has a so-so page which is at least | reasonably accessible and equipped with a good references | section: | https://en.wikipedia.org/wiki/Gravitational_interaction_of_a... | | - -- | | [1] https://profmattstrassler.com/articles-and- | posts/largehadron... | | "The standard shorthand, "the proton is made from two up quarks | and one down quark", is really a statement that the proton has | two more up quarks than up antiquarks, and one more down quark | than down antiquarks. To make the glib shorthand correct you | need to add the phrase "plus zillions of gluons and zillions of | quark-antiquark pairs." Without this phrase, one's view of the | proton is so simplistic that it is not possible to understand | the LHC at all." (for which see a later followup, | <https://profmattstrassler.com/articles-and- | posts/largehadron...>) | Filligree wrote: | People have tossed the idea around, and it makes sense to | check, but I'm not aware of anyone who seriously thought it | might have negative mass. | pmarreck wrote: | This has long been one of my justifications for the "maybe | intelligent extraterrestrial pilot" theory of UFO's; now that | theory is weakened... | thsksbd wrote: | Why did they think it would have negative gravitational | attraction? I always thought it would be attractive mass and | didn't realize that was to be proven. | | EDIT: now that I think about it, what are the implications for | the "arrow of time" arguments? | nyssos wrote: | > Why did they think it would have negative gravitational | attraction? | | They didn't. There are very strong theoretical reasons (among | them, CPT symmetry) to expect antimatter to gravitate normally. | But it's still good to actually check. | mst wrote: | > our greatest science-fiction hope for achieving warp drive has | completely evaporated | | Damnit, "was completely annihilated" was Right. There. | lend000 wrote: | Take the following with a huge grain of salt: | | The controversial scientist Bob Lazar, the guy who made Area 51 a | household name, put out a video when he first went public that, | regardless of whether you think he's full of shit or not, is | pretty interesting and better than most sci-fi in terms of | explaining how an advanced vehicle might travel without | propulsion and not be limited by the speed of light [0]. | | His premise is that the strong nuclear force is a purely | attractive sub-force of gravity that affects spacetime in the | same way, and that there are heavier elements that were created | in star systems with much more energy than our sun and its | predecessors. These stable, high atomic weight elements | (specifically element 115, which was synthesized and added to the | periodic table much later) have large nuclei past a certain size | threshold, in which the strong (gravitational) force reaches | nonlinearly beyond the nucleus and can be amplified and focused | (somehow?) into a gravitational wave that distorts spacetime. He | claims that antimatter annihilation, also fueled by the same | element, is the source of power for that amplification. | | [0] https://www.youtube.com/watch?v=b_Lre3B6SUQ | empath-nirvana wrote: | Wouldn't it be more interesting to learn real physics instead | of made up stuff? | ben_w wrote: | Real physics requires ten simultaneous partial differential | equations for the gravity, and 17 space filling complex- | valued fields for the particles in the standard model, and | they don't even work right with each other. | | Interesting to me, sure, but I'm enough of a nerd than in the | team building exercise today where we all had to write a one- | word summary of ourselves on a post-it note in secret, then | guess which post-it corresponded to which person, even though | we were all nerds and I wrote "nerd" on my post-it, everyone | else immediately knew it was mine without any debate. | withinboredom wrote: | I enjoy fantasy physics more than regular physics by a pretty | large margin. | lend000 wrote: | It's not like you or I are actually going to do anything | based on our limited understandings of particle physics, so | fortunately it's irrelevant. But I'm not one of those people | who says every year that we understand everything (until next | year when some updates come out and they reiterate their | position). | | Contemplating why anything exists at all is much more | interesting than inaccessible and incomplete particle physics | anyway. | moffkalast wrote: | The only thing that real physics is good for is telling | enthusiastic people that "ackchyually that's not possible | because of these equations I won't bother explaining, trust | me bro". Made up stuff wins every time. | [deleted] | DonnyV wrote: | No warp drive, no artificial gravity. You really want to kill my | morning. :-( | FridgeSeal wrote: | We truly live in the universe with most boring set of physical | laws. | | Hard light speed cap, no anti-gravity, entanglement can't be an | information channel, no warp drives. It's like we got stuck on | the "no fun" setting hahaha. | charred_patina wrote: | If you like sci-fi, you should read the Three Body Problem | series. I won't post any spoilers but the "no fun" setting is | a plot point. | asah wrote: | Wait until you hear about the situation in the middle east... | :-( | tomrod wrote: | I mourn that the sectoral conflict has resulted in yet more | violence. People can live pluralistically -- it's been proven | many times over to work well and in the best interest of all | people involved. | | That said, it's pretty far removed from a conversation on | antimatter. | fabulous265 wrote: | Even mathematically it doesn't make any sense: we would need to | go to a causally disconnected region of spacetime to be able to | go faster than the speed of light, but that's just not feasible. | Once you go to that causally disconnected region of spacetime, | the only outcome is to go to a singular point in space (even | though you can go back and forth in time, theoretically at least) | : if that sounds familiar to you, it's because it is well | represented into the movie <<interstellar>> and indeed he goes to | a region causally disconnected to ours: a black hole. | jameshart wrote: | If its intention was to illustrate realistic causal | disconnection, _Interstellar_ does a pretty poor job. | | What with the causal loops and so on. | outworlder wrote: | So you don't think it's realistic that 'love transcends | dimensions of space and time'? :) | jameshart wrote: | Or that the only thing standing between humanity and the | ability to build space craft capable of colonizing other | planets is getting the right numbers to plug into a | 'gravity equation'? | | Having been sold on the movie by people telling me the | science was "realistic"... the reality was disappointing. | lordfrito wrote: | > getting the right numbers to plug into a 'gravity | equation' | | Those are what I like to call "load-bearing" numbers. :) | | There's so much science _daydreaming_ in what passes for | the science press that people think all of our problems | will be solved once the smart people (or quantum | computers) find the magic formula and those elusive load- | bearing numbers. | | Half the people here understand physics, and the sheer | impossibility of the task due to the relative magnitudes | involved, and have resigned themselves to "we better | learn to live on this ball together as it's all we're | ever going to have". The other half daydream about | magical solutions that marvel movies tell us exist, we're | just waiting for an Elon Musk or Tony Stark to discover | it and then humanity enters a golden age. | perihelions wrote: | Related thread: | | https://news.ycombinator.com/item?id=37679584 ( _" Observation of | the effect of gravity on the motion of antimatter (nature.com)"_; | 68 comments) | moomoo11 wrote: | We should just build spaceships that are "tied" to a small planet | or moon. Then just yeet that over massive distances. | | Imagine being an alien species and humans roll up pulling a small | star or something. | eppp wrote: | Where do you get the energy to move that amount of mass? | Xymist wrote: | Start with a big planet. Orbit a gas giant, burn most of it | for fuel to get up to sufficient speed that your relativistic | mass exceeds that of what is left (and to stop yourself | zooming off in the meantime) and then pull the remainder | along with you. | jackcosgrove wrote: | I know there are a lot of hopes for warp travel, but doesn't it | make more sense to decouple (most of) space travel from moving | matter? | | To do this you need to decouple consciousness from bodies, which | isn't possible with humans given that our consciousness grows | along with our brains and everyone's structures are unique. But | it is possible with artificial intelligence. Once consciousness | has been digitized, you can beam it at the speed of light to a | receiver. | | You still need to physically install the receiver somewhere, | which is why I said only most of space travel could be non- | physical. But once that receiver is in place, you can beam | information to it and construct bodies onsite at minimal cost. | | This just seems like the kind of space travel the universe | _prefers_ , since it minimizes action. Energy is for travel, and | matter is for staying put. | | The stupendous amounts of energy required for warp travel just | seem wasteful, when instead of adapting the universe to life we | could adapt life to the universe. | jvanderbot wrote: | We need to let go of the "Ship full of brave men" meme of space | exploration. | | It'll have to be robots, probably very small robots, some kind | of solar sail / exogenous energy source (or maaaaaybe fusion?), | and probably either a copy of some human's consciousness in a | machine, or a bunch of fertilized frozen embryos, or both. | | And even then only after a lot of gene / tree bombing of the | target planet to have any hope of making it liveable. | Cthulhu_ wrote: | A very believable theory is that this is how life on earth | started - another ancient civilization shooting the building | blocks of life everywhere and hoping something sticks. | (panspermia?) | | But while this is cute, given the inexorable passage of time | and entropy, any evidence that life was planted by ancient | aliens has long gone. If it was e.g. a spaceship or meteor, | it's been swallowed up by the earth and into the mantle by | now. | | Unless there's a new source - like aliens making contact - it | will remain unknowable. | Maken wrote: | You are essentially describing Clarke's Rama spaceship. | jvanderbot wrote: | Yeah - I don't think it's so clever that nobody has thought | of it. It just seems obvious when you look enough into how | hard inter-stellar travel will be. | | But making machines that operate for 100 years seems doable | if we try. | zzzeek wrote: | how are you so sure that anyone else besides you is actually | conscious ? you might be the only conscious being in the | universe. the whole universe is yours. you've already traveled | the entire thing. | | I'm conscious too but that's in my own universe, running in | parallel to yours. | | the "once consciousness has been digitized" step would have | many hurdles of similar complexity to meet before simplistic | 21st century manipulation techniques would ever apply. | tomrod wrote: | > how are you so sure that anyone else besides you is | actually conscious ? you might be the only conscious being in | the universe. the whole universe is yours. you've already | traveled the entire thing. | | Because other's express things that I in my wildest dreams | couldn't have imagined. | | I think solipsism dies when epistemic humility comes into the | picture. | zzzeek wrote: | i never really get the notion people sometimes have that | consciousness arises from a specific, physically | identifiable structure in the brain, where a person | actually seems to have a "self", looking out of their eyes | from inside their heads, and furthermore is "atomic" in | that sense; it can't be split in half (because which half | would the "self" be present in then?), yet there can exist | no structure that produces the same output without the | "they are looking out of their eyes from inside their | heads" part. | | "self looking outside of my head" strikes me as so | completely paradoxical that explanations such as each | consciousness is its own universe seem just as plausible as | any other. it does not mean the person you are talking to | is not conscious, just that their consciousness is playing | out in a parallel copied universe. | I_Am_Nous wrote: | In the past, this was understood to be the soul and you | are correct when you describe it as atomic, though | depending on which tradition is describing the soul it | can have further attributes. My username is based on such | a tradition -- the Nous (pronounced like noose) is | considered the eye of the soul. Extrapolating that | further, we focus the eye of our soul on whatever we want | to, which can be ourselves, worldly aspirations, or | spiritual aspirations. | | This would be considered the free will we are given at | the basest level - we get to choose what we focus our | soul on, and that can be changed at any moment. Such a | tradition would say that since we are a body/soul | composite, whatever we focus our soul on, our body | willingly and immediately focuses on as well, for good or | ill. | tomrod wrote: | I actually really enjoyed some of Sam Harris' "Waking Up" | meditation series for this. Not a usual activity for me. | However, I greatly enjoyed reflecting on the notion of | "there is no self." | | [0] https://www.youtube.com/watch?v=CN-_zzHpcdM | zzzeek wrote: | Yes the "self" is an illusion, but at least for me, | there's an _emergent_ illusion /whatever of "hey im | inside this head looking out", which we claim arises from | a physical brain structure. if this structure were | divided in some way, does my current "self" vanish and | two new consciousnesses arise? do those new | consciousnesses have memory, so one is on one side of the | room, the other is on the other ? at what point is my | current "self" no longer viable such that it vanishes? | | edit: looks like HN is throttling me again. hmm but not | edits. well that's fun | tomrod wrote: | Weird. Your comment came through just fine. | | I see your thought on emergence of self. Almost like self | is equivalent to consciousness. Without a notion of self, | you are part of a larger system with will. | | Stemming the claim that there is no free will, I know the | argument, but don't agree to it as what we observe (that | people make choices at least some of the time) goes | against claimed theory (that our choices are random | chemistry-driven outcomes based on state of the world). | I'm not terribly deep in the area, though, and welcome | correction or thoughts. | dghughes wrote: | Sounds like The Egg by Andy Weir | http://www.galactanet.com/oneoff/theegg_mod.html | bloopernova wrote: | Never read that before, thank you for sharing, it's a great | little story! | dghughes wrote: | Yeah it's a blast goes well with Isaac Asimov's The Last | Question. | | Andy Weir also wrote The Martian. | bloopernova wrote: | I've just recently been reading Project Hail Mary, and | enjoyed so much I'm on my 2nd re-read! | | The Martian is also great. | qingcharles wrote: | Two of my favorite sci-fi books of all time. | | Just found out Project Hail Mary movie is in pre- | production... | eternityforest wrote: | We don't know for sure that AI would be conscious. Teleporting | super intelligent zombies around isn't all that interesting. | I_Am_Nous wrote: | Here's the existentialism I was looking for :) | | I'm not sure how we can verify that empirically. Current LLM | AI will hallucinate about the feelings it "has" and argue why | it is a person, but only because it was trained on human | language. The more human we make something seem, the more we | blur the line until we might have a day where people upload | their consciousness permanently without knowing if "they" | will wake up inside the computer or just some copy of | themselves that answers all the "don't kill me, I'm a real | person" questions will wake up in the computer. | | Human software is still intrinsically tied to human hardware, | so this seems like it would be far easier to create zombies | than true humans, even if the checksum matches after an | interstellar transmission. | bluecheese452 wrote: | Having my consciousness be trapped in a computer sounds | terrifying. Like being completely paralyzed but still | conscious. | I_Am_Nous wrote: | From a "future harm" perspective, if I have a full, | functional backup of me somewhere, who's to say someone | doesn't hack it down the line and torture copies of me? | What's stopping an AI from torturing my backup because I | didn't help fund AI research? | | Me never getting uploaded in the first place - that's | what's stopping it :) | moffkalast wrote: | Well can you prove you're conscious? I'm just gonna assume | you're not otherwise. That's the kind of benefit of the doubt | we'll be giving AI apparently. | leereeves wrote: | > and construct bodies onsite at minimal cost. | | Once established, perhaps, but microchips aren't easy to build. | You'd have to send a lot of infrastructure before you could | create AI brains on another planet. | zaptrem wrote: | This is how interstellar travel worked in Altered Carbon. | salawat wrote: | I was a Traveller once, then I suffered a qbit flip in | transmission the checksums couldn't compensate for. Now, I | just love Coca-Cola brand Mango Fantastic soda, and hunting | indigents for sport! | jfengel wrote: | A lot of people seem weirdly aggrieved by the limit of the | speed of light. It's not really the reason we can't go to space | -- if you had magic energy density you could go to the stars in | as little time as you wish, due to relativity. (Weird stuff | happens when you try to come back, but nobody ever seems to | care about that anyway.) | | I think people hear "Einstein said you can't go faster than the | speed of light" and think, "Surely I can figure out how to be | smarter than Einstein". It appears to be parallel to the ones | who get cranky when being told that Newton says you can't make | a perpetual motion machine. | | I suspect that they don't spend as much time thinking about the | brain-in-a-box version is that it opens up too many scenarios | that are hard to think about. If you decouple consciousness | from bodies, who are you? Why not make multiple copies? Why go | anywhere at all, when you could just stick the sensors there? | | People really want the cowboys in space, and get aggrieved that | somebody told them they can't. So they focus on overcoming a | limit that seems like it can be solved just by thinking really | hard, and leave the engineering details to the peons with | calculators. | api wrote: | Agreed. Thing is we can still have our cowboys in space. The | solar system is insanely huge and can be traversed in human | time scales with technology based on known physics. The | baseline world of The Expanse (minus the alien stuff) is | entirely feasible. | | Interstellar travel is entirely possible too as long as you | are okay with it being effectively a one way trip. Suspended | animation is probably possible; we can do it to some animals | and individual organs. So you go to sleep for a very long | time and wake up in another star system. It would make the | most sense to send a bunch of robots to build yourself a | settlement first. Or alternatively send sentient AI which | would find it much easier than humans to simply turn itself | off for the duration of the trip. | tgv wrote: | Why would you put an AI on another planet? It's easier to | transfer images and other data back here for everyone and | everything to perceive. | | > construct bodies onsite at minimal cost | | That requires a bit more than a receiver. You'd have to build a | robot factory, which requires energy production which requires | mining which requires heavy machinery, which etc. | btilly wrote: | Reaction time and autonomy. | | Driving on Mars is incredibly slow in part because the signal | has to get to and from us for every decision. And if | communication is blocked for any reasons, the vehicle is | stuck. | | AI on Mars fixes both problems. | lloeki wrote: | > the signal has to get to and from us for every decision. | And if communication is blocked for any reasons, the | vehicle is stuck | | Curiosity and Perseverance have a limited form of autonomy | to work around that, as both can AutoNav: the former | alternating standstill thinking and movement, the latter | "thinking while driving". | | https://mars.nasa.gov/news/8980/nasas-self-driving- | persevera... | moffkalast wrote: | That by itself isn't all that clever, since any half | versed roboticist can do the same with some trial and | error. | | What's seriously impressive about it is that it works in | real time on an absolute brick of a 233 MHz PowerPC from | the 90s. Like, an ESP32 probably outperforms it. | ptha wrote: | Apparently the Perseverance Mars Rover has some self- | driving capability: | | _With the help of special 3D glasses, rover drivers on | Earth plan routes with specific stops, but increasingly | allow the rover to "take the wheel" and choose how it gets | to those stops. Perseverance's auto-navigation system, | known as AutoNav, makes 3D maps of the terrain ahead, | identifies hazards, and plans a route around any obstacles | without additional direction from controllers back on | Earth._ [1] | | The mission has used AI not just for driving the rover, but | also landing and targeting instruments. [2] | | [1] https://phys.org/news/2022-04-nasa-self-driving- | perseverance... [2] | https://www.enterpriseai.news/2021/02/19/perseverance- | rover-... | salawat wrote: | >Perseverance's auto-navigation system, known as AutoNav, | makes 3D maps of the terrain ahead, identifies hazards, | and plans a route around any obstacles without additional | direction from controllers back on Earth. | | ...in spite of this autonomy, Perseverence has a few | major problems. It is famous for the severity of it's | road rage and intolerance for human drivers, bicyclists, | parked emergency vehicles, and pedestrians. Tests show a | disturbing tendency toward "eliminating the human | element" from it's driving environment to simplify route | planning. The lengths the system will go to to achieve | this were a major frustrator in early development, and | initially attracting the interest of [REDACTION] for | [REDACTION] due to [REDACTION] with an effective [THE | REDACTION MACHINE IS BROKEN, FURTHER INQUIRIES SHOULD BE | ROUTED THROUGH TOM]. | | Mission planners at NASA found the risk involved with | deployment to the Red Planet agreeable, but note that any | ongoing colonization efforts will involve having to put | the system down for the safety of any eventual colonists. | ptha wrote: | That's a slightly extreme route planning optimisation, | but reminded me of UPS removing _left turns_ (in Right | Hand Side driving countries like US) from their route | planning to save fuel, lives, C02 emissions [1] | | [1] https://edition.cnn.com/2017/02/16/world/ups-trucks- | no-left-... | idiotsecant wrote: | Our local system has a definite cap on processing power. | Eventually it would be necessary to find more power to do | more thinking. | breuleux wrote: | > But it is possible with artificial intelligence. Once | consciousness has been digitized, you can beam it at the speed | of light to a receiver. | | That may not remain true. The ability to serialize | consciousness does not come for free, it requires extra wiring | to carry all information out of the system or to stream it in, | which is an intrinsic inefficiency. All other things kept | equal, a brain's performance ceiling is higher if you only | locally connect the units/neurons that need to be connected and | nothing else, but in doing so you give up digitizability. It is | entirely possible that future AI, in order to be performant | enough, will lose the ability to be transmitted in the way that | you describe. | quickthrower2 wrote: | Speed of light limit is a big problem though. How do you | explore the universe if you can't catch up with it? Even with a | Googol of human lifeforms running as AI spread out across it in | a mesh, it is still expanding too fast! | Udo wrote: | This is a good argument for transhumanism. People seem to have | a problem with the speed of light since without FTL, unmodified | humans cannot meaningfully travel interstellar distances - and | pop culture entertainment has surreptitiously sold us on this, | if only because otherwise the timeframes and types of bodies | involved would not be "relatable" anymore for the common types | of drama we consume. | | _> Once consciousness has been digitized, you can beam it at | the speed of light to a receiver._ | | In principle yes, however, the energy required is still | dramatic and bandwidth would probably still be a problem. It | seems to me the default option would be to physically send non- | aging transhumans, or virtualized/uploaded brains, or people in | stasis (or a combination of these) using non-relativistic | speeds. | jackcosgrove wrote: | > virtualized/uploaded brains | | That's a good point. Something about "never underestimate the | bandwidth of a U-Haul carrying a bunch of tape drives." | distract8901 wrote: | It's been really weird seeing all these warp drive and | antigravity people crawling out of the woodwork in response to | this result. | | I have _never_ heard of antimatter proposed for _anything_ other | than an energy source /storage. Not even in the oldest SciFi | stories. Where did this idea even come from? It seems to have | just appeared from nowhere as a way to feel bad about an | otherwise inconsequential result. | | Very strange | scionthefly wrote: | Theoretical warp physics -- the real kind, like Alcubierre, not | the Wesley Crusher kind -- proposes that a source of negative | mass would be critical to the creation of a warp field. | | Antimatter as part of an energy storage system for propulsion | is still a good idea. They'll just have to look elsewhere for | that property, or modify the theory to work on different | principles. Eric Lentz is working in that direction and doesn't | think negative mass/energy is needed. | empath-nirvana wrote: | But we've seen anti matter and we already _know_ it doesn't | have negative mass. | distract8901 wrote: | >Theoretical warp physics -- the real kind, like Alcubierre, | not the Wesley Crusher kind -- proposes that a source of | negative mass would be critical to the creation of a warp | field. | | Well, yes, that's always been the crucial missing component | from Alcubierre's design, but I've never seen anyone suggest | antimatter would have negative mass or energy before now. The | talk has always been about some hypothetical exotic matter | jillesvangurp wrote: | Not weird, just irrational. If warp drives were possible, | aliens might be traveling to us before we'd invent them. That | doesn't seem to be the case. There are a lot of explanations | for that, including a few that involve conspiracy theories | where this did in fact happen but we are being kept in the dark | about it. But the easiest one would be that it hasn't happened | because it isn't possible. Faster than light travel not being | possible, it's unlikely for there to be a coincidence of any | other intelligent species to exist within tens/hundreds of | light years of our tiny little corner of the universe exactly | at the moment where we hit enlightenment, steam machines, and | rocketry in the time frame of about 250 years. Never say never | of course but it does sound astronomically unlikely when you | put it like that. | | In the absence of any nearby aliens to travel to, what exactly | is the value of traveling at warp speed to some desolate bit of | universe? We'd get nowhere a lot faster is about the most | positive thing you could say about that. Most sci-fi is | premised on the notion that we're not alone and that there is | this wealth of interactions (good and epically bad) to be had | on the far side of any worm hole that we travel through at warp | speed. But we have zero proof of that nor a way to travel in | such a fashion. Or even the confirmation of the possibility of | being able to do so. Fantasy and reality are not really aligned | here. | deafpolygon wrote: | Looks like we're gonna have to bet on Spore drives. | timbit42 wrote: | What about jump drives in Battlestar Galactica? | pelorat wrote: | Well, yeah, anti-matter is not negative matter, it's more like | mirror-matter. Negative energy and negative matter probably | doesn't exist in our universe. Negative matter would require an | anti-photon that could in theory cause energy to be destroyed if | it interacted with a regular photon. | | There are four types of matter, of which two are theoretical: | positive-matter, positive-anti-matter, negative-matter, negative- | anti-matter. Only the first two exist in our universe as far as | we know. | dghughes wrote: | >the only requirement was something that anti-gravitated: | something like "negative energy" | | A bit more than that. Didn't it also require the energy | equivalent to the output of a small star? | pmarreck wrote: | Honestly, this does sound like an intimidatingly high amount of | energy, but look at the progress of computational power since, | say, 1973, 50 years ago. If the same advances in physical | control of energy had taken place, who knows where we'd be | today | ben_w wrote: | I'm not sure how many USD/GFLOPS you could get in '73, but in | '84 they were Cray X-MP/48 costing $15,000,000 / 0.8 GFLOPS | (inflation adjusted $600B/TFLOP); today we get RX 7600 | costing $269/21.5 TFLOPS ($12.51/TFLOP). | | If energy prices changed that much while spending per year | remained constant, your usage would go up by a factor of | about 48 billion. This might happen if we develop Von Neumann | probes and disassemble a planet to turn it into energy | collecting satellites, and some not-even-crazy estimates | suggest this is indeed possible over 50 years. | WJW wrote: | The problem with that comparison is that we are not even | close to the theoretical limits for computational density, | while we are quite close to the limits for efficiency in | things like turbines. | arethuza wrote: | The Tsar Bomba (5.3YW) managed about 2% of the power output of | the Sun (384YW) - admittedly not for very long though... | | So Teller's _Sundial_ design was aimed at 10Gt so ~200 times | more than the Tsar Bomba as tested. | | So Sundial's peak power output would perhaps have been roughly | 1RW? | | Edit: Maybe you power the Warp drive with a sequence of | Sundials.... in a sort of Orion like approach? :-) | | Edit2: So about a billion Sundials a second and you're good to | go? | | Edit3: Usual upper limit of yield per mass is about 6Mt per t - | so a Sundial would be about 1500t. So that would be burning | about 1.5 Tt of bombs a second? | api wrote: | > The Tsar Bomba (5.3YW) managed about 2% of the power output | of the Sun (384YW) | | TIL | | You know what's even more amazing/frightening? There is no | power limit for hydrogen bombs. You could take a bomb like | the Tsar Bomba or Castle Bravo and _use that as a blasting | cap to trigger an even larger fusion stage_. ... and on, and | on, in a vast nested turducken of kaboom. | | One of the ideas to deflect a planet killer asteroid would, | if we had time, be to land there and build a base and | assemble such a mega-bomb deep underground. | arethuza wrote: | "There is no power limit for hydrogen bombs" | | Edward Teller (who else) got there first! | | https://blog.nuclearsecrecy.com/2012/09/12/in-search-of-a- | bi... | | A 1Gt primary (Gnomon) igniting Sundial to give 10Gt. | NoMoreNicksLeft wrote: | Can you only bump it an order of magnitude per stage | though? Seems inefficient. | | Sounds like one of the defense contractor MBAs got ahold | of the plan. | arethuza wrote: | I suspect that limit might be because a Sundial would be | physically huge - 1500t or so. | lttlrck wrote: | "turducken" never heard of it and what a perfect word in | this context LOL! | | https://en.m.wikipedia.org/wiki/Turducken | dboreham wrote: | The 3D version of turtles. | CamperBob2 wrote: | _One of the ideas to deflect a planet killer asteroid | would, if we had time, be to land there and build a base | and assemble such a mega-bomb deep underground._ | | Problem: Giant-sized asteroid on collision course with | Earth | | Solution: Build giant bomb and nuke it | | Problem: 843 medium-sized radioactive asteroids on | collision course with Earth | ben_w wrote: | Hawking wrote in A Brief History of Time: | | > John Wheeler once calculated that if one took all the | heavy water in all the oceans of the world, one could build | a hydrogen bomb that would compress matter at the center so | much that a black hole would be created | ben_w wrote: | Depending on the model, anything from the mass-energy of a few | tons to several times the universe. | | Apparently a few models work with positive mass, but I'm | reading headlines for that, I can't follow field equations. | NoMoreNicksLeft wrote: | That's just a scaling issue. ___________________________________________________________________ (page generated 2023-10-09 23:00 UTC)