18 ms·

Warp drive's best hope dies, as antimatter falls down

194 points by WithinReason 3y ago

perihelions 3y ago
Related thread: https://news.ycombinator.com/item?id=37679584 https://news.ycombinator.com/item?id=37679584 ("Observation of the effect of gravity on the motion of antimatter (nature.com)"; 68 comments)
esc861 3y ago
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 https://iopscience.iop.org/article/10.1088/1361-6382/abe692
- captn3m0 3y ago
  We’ve lost the “best hope”, not all hope.
dghughes 3y ago
>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?
- ben_w 3y ago
  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.
- arethuza 3y ago
  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 3y ago
    > 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 3y ago
      "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-bigger-boom/ https://blog.nuclearsecrecy.com/2012/09/12/in-search-of-a-bi... A 1Gt primary (Gnomon) igniting Sundial to give 10Gt.
      - NoMoreNicksLeft 3y ago
        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 3y ago
        I suspect that limit might be because a Sundial would be physically huge - 1500t or so.
    - lttlrck 3y ago
      "turducken" never heard of it and what a perfect word in this context LOL! https://en.m.wikipedia.org/wiki/Turducken https://en.m.wikipedia.org/wiki/Turducken
      - dboreham 3y ago
        The 3D version of turtles.
- pmarreck 3y ago
  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
  - WJW 3y ago
    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.
    - shiroiuma 3y ago
      Anything involving a Carnot cycle is a rather primitive usage of energy, so I'm not surprised that turbines are close to their peak efficiency since humans have been using them for at least a century now. More modern forms of energy usage will skip the whole heat-cycle skip and just directly produce electricity from some other energy source. We're still in early stages of much of that; just look at how much PV (solar) efficiency has improved in the last few decades. And we've barely even looked at what we can do with nuclear power[1]. 1. https://en.wikipedia.org/wiki/Fission_fragment_reactor https://en.wikipedia.org/wiki/Fission_fragment_reactor
      - WJW 3y ago
        PV has increased from a <10% percent efficiency in the 80s to 25-30% now for commercially available panels. They can grow another 3.3x in efficiency at most, hardly comparable to the doubling every few years that semiconductors have had. The wikipedia link you provided contains the following snippet: > and can achieve efficiencies of up to 90% instead of 40-45% attainable by efficient turbine-driven thermal reactors. A doubling of efficiency is extremely nice, don't get me wrong. But after you get to 90% there is simply not much further to go. On the other hand, semiconductor production has probably not even reached 1% of what is achievable. Non-flat structures are still seen as incredibly advanced, let alone true 3D chip manufacturing. Bulk energy production will never see improvements comparable to those found in semiconductor manufacturing, simply because the systems don't have nearly as much "efficiency space" left to grow into.
- NoMoreNicksLeft 3y ago
  That's just a scaling issue.
DonnyV 3y ago
No warp drive, no artificial gravity. You really want to kill my morning. :-(
- asah 3y ago
  Wait until you hear about the situation in the middle east... :-(
  - tomrod 3y ago
    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.
- FridgeSeal 3y ago
  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.
  - DonnyV 3y ago
    "It’s like we got stuck on the “no fun” setting" Thats gold my friend. LOL
  - charred_patina 3y ago
    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.
    - FridgeSeal 3y ago
      Yeah I’ve read the 3-body-problem books, didn’t enjoy them, but I’m well aware of the mechanic you’re speaking of.
davedx 3y ago
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 3y ago
  The author addresses this (in a very condescending way) in the last couple paragraphs. But yes, I tend to agree with you.
  - oldbbsnickname 3y ago
    It reminds me of NASA's EM Drive debacle from 2015.
phkahler 3y ago
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 3y ago
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.
- elil17 3y ago
  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 3y ago
    Hum, How can they be sure that what is hitting the plate is still antimatter? (Or only antimatter?)
    - ben_w 3y ago
      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.
- 3y ago
mr_mitm 3y ago
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 https://twitter.com/malcubierre/status/362011821277839360
- marcosdumay 3y ago
  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 3y ago
    >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
    - lawlessone 3y ago
      >The best you can do is drag the warp field behind your ship with normal thrusters. Ok we can build a warp trebuchet.
      - distract8901 3y ago
        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.
netbioserror 3y ago
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?
- Filligree 3y ago
  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.
- Khoth 3y ago
  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 3y ago
  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 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_antimatter https://en.wikipedia.org/wiki/Gravitational_interaction_of_a... - -- [1] https://profmattstrassler.com/articles-and-posts/largehadroncolliderfaq/whats-a-proton-anyway/ 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/largehadroncolliderfaq/whats-a-proton-anyway/proton-collisions-vs-quarkgluonantiquark-mini-collisions/ https://profmattstrassler.com/articles-and-posts/largehadron...>)
jackcosgrove 3y ago
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.
- zzzeek 3y ago
  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 3y ago
    > 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 3y ago
      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.
gs17 3y ago
>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.
- thsksbd 3y ago
  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 3y ago
    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.
    - Izkata 3y ago
      > 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.
    - thsksbd 3y ago
      "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.
- aetherson 3y ago
  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 3y ago
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 3y ago
  > 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.
pelorat 3y ago
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.
moomoo11 3y ago
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 3y ago
  Where do you get the energy to move that amount of mass?
  - Xymist 3y ago
    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.
  - svachalek 3y ago
    Here's a proposal: https://www.youtube.com/watch?v=v3y8AIEX_dU https://www.youtube.com/watch?v=v3y8AIEX_dU
mst 3y ago
> our greatest science-fiction hope for achieving warp drive has completely evaporated Damnit, "was completely annihilated" was Right. There.
deafpolygon 3y ago
Looks like we're gonna have to bet on Spore drives.
- timbit42 3y ago
  What about jump drives in Battlestar Galactica?
pmarreck 3y ago
This has long been one of my justifications for the "maybe intelligent extraterrestrial pilot" theory of UFO's; now that theory is weakened...
distract8901 3y ago
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 3y ago
  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.
  - distract8901 3y ago
    >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
  - empath-nirvana 3y ago
    But we've seen anti matter and we already _know_ it doesn't have negative mass.
- jillesvangurp 3y ago
  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.
mperham 3y ago
Quanta and BigThink are such great sites, pumping out high quality science journalism.
- rilindo 3y ago
  BigThink, ironically, is sponsored by the Charles Koch Foundation.
  - WendyTheWillow 3y ago
    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/ https://bigthink.com/our-mission/ [1] https://www.crunchbase.com/organization/freethink-media/company_financials https://www.crunchbase.com/organization/freethink-media/comp... [2] https://www.linkedin.com/company/bedrockcap/ https://www.linkedin.com/company/bedrockcap/ [3] https://www.linkedin.com/company/mac-venture-capital/ https://www.linkedin.com/company/mac-venture-capital/
    - rilindo 3y ago
      It is on their web site: https://bigthink.com/people/charles-koch-foundation/ https://bigthink.com/people/charles-koch-foundation/
      - WendyTheWillow 3y ago
        That says nothing about sponsorship. At best, it implies a vague partnership, which is fundamentally different.
fabulous265 3y ago
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 3y ago
  If its intention was to illustrate realistic causal disconnection, Interstellar does a pretty poor job. What with the causal loops and so on.
  - outworlder 3y ago
    So you don't think it's realistic that 'love transcends dimensions of space and time'? :)
    - jameshart 3y ago
      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 3y ago
        > 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.
pnpnp 3y ago
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 3y ago
  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?
  - aldousd666 3y ago
    Antimatter was to be used to generate the energy required, by annihilation of regular matte, not the antigravity itself. "Exotic matter" is undefined as of yet in that it could still exist as something else. Some people are confusing the two ideas, even though some (few) people probably did actually think anywhere would anti-gravitate, as it were.
SkyMarshal 3y ago
> 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?
- johnchristopher 3y ago
  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".
- Agathos 3y ago
  "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).
jedberg 3y ago
It's ok, we still have 40 more years to figure it out.
- ruined 3y ago
  that's quite optimistic. i'd give us fifteen tops
  - stevula 3y ago
    It's a reference to the year warp drive will be invented by Zefram Cochrane in the Star Trek universe.
- nv2156 3y ago
  Yeah once Dr Cochrane starts working on it :).
  - jedberg 3y ago
    Give him a break, he isn't even born yet!
  - WendyTheWillow 3y ago
    Maybe we should start naming every single person born as of now-ish, Zefram Cochrane, just to be safe...
    - qingcharles 3y ago
      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
deleted 3y ago
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OhNoNotAgain_99 3y ago
[dead]
lend000 3y ago
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 https://www.youtube.com/watch?v=b_Lre3B6SUQ
- empath-nirvana 3y ago
  Wouldn't it be more interesting to learn real physics instead of made up stuff?
  - withinboredom 3y ago
    I enjoy fantasy physics more than regular physics by a pretty large margin.
  - lend000 3y ago
    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.
    - 3y ago
qingcharles 3y ago
At this rate it is going to be easier to simply emulate the entire universe (aka Devs) and just travel virtually around space-time that way. Then we can just stay home and eat cheese puffs.
- rpastuszak 3y ago
  The universe is just a matryoshka of recursive couch potatoes eating cheese puffs.
  - fsckboy 3y ago
    matryoshka's all the way down doesn't sound that great. OTOH, cheese puffs all the way down sounds pretty perfect.
  - oldbbsnickname 3y ago
    Don't forget that we also only drink Mountain Dew Zero because water is yucky, and we have obligatory pet turtles with recursive acronym names.
aldousd666 3y ago
I'm glad they settled this one; however, to my knowledge nobody thought Anti-Matter meant "Anti-gravity" w/rt Alcubierre warp drive. That's not what they meant by 'exotic matter.' But ok. sure. There was doubt that exotic matter could exist at all, and nobody had doubts that anti-matter could exist. I think there is something lost in the translation here. (No I'm not saying that warp drive still must be possible, I just think people, including the article writers, are conflating things.)
MR4D 3y ago
We can focus light waves , sound waves, x-rays, etc. Why can’t we figure out how to focus gravity waves?
- Frummy 3y ago
  We can do a lot of stuff with energy in various forms but gravity is just from mass which is quite difficult to control. Essentially we suck at fission and fusion at meaningful scales and we have a very narrow capability as well. I mean, to destroy mass equivalent to Mars in a short time frame is a cosmically cataclysmic nuke, then to not waste that energy, so you efficiently capture it and recreate the mass elsewhere in one huge fusion reaction. Maybe I talked past you and just daydreamed about Dr Manhattan stuff, maybe what it takes to emit gravity at will at some location, is much more difficult than just redirecting it which I dont have the tools to daydream about.
ls612 3y ago
Doesn’t dark energy mathematically manifest as “negative mass”? Or am I misunderstanding what physicists mean by that?
omneity 3y ago
My understanding as a non-physicist is that the specific requirement for a warp bubble Alcubierre-style is negative mass. Now this negative mass is theorized to come from some form of exotic matter, which could but doesn’t have to be antimatter. The jury is still out on this one. As a fan of space travel, it seems the prospect of a warp drive is still not budging much from 0 chance. But that’s okay, we’re also not worse off where we started.
nirav72 3y ago
It seems that the limits of physics are itself the great filter.

194 points by WithinReason 3y ago

Related thread: https://news.ycombinator.com/item?id=37679584 https://news.ycombinator.com/item?id=37679584 ("Observation of the effect of gravity on the motion of antimatter (nature.com)"; 68 comments)

esc861 3y ago

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 https://iopscience.iop.org/article/10.1088/1361-6382/abe692

captn3m0 3y ago
We’ve lost the “best hope”, not all hope.

dghughes 3y ago

>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?

ben_w 3y ago
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.
arethuza 3y ago
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 3y ago
  > 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 3y ago
    "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-bigger-boom/ https://blog.nuclearsecrecy.com/2012/09/12/in-search-of-a-bi... A 1Gt primary (Gnomon) igniting Sundial to give 10Gt.
    - NoMoreNicksLeft 3y ago
      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 3y ago
        I suspect that limit might be because a Sundial would be physically huge - 1500t or so.
  - lttlrck 3y ago
    "turducken" never heard of it and what a perfect word in this context LOL! https://en.m.wikipedia.org/wiki/Turducken https://en.m.wikipedia.org/wiki/Turducken
    - dboreham 3y ago
      The 3D version of turtles.
pmarreck 3y ago
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
- WJW 3y ago
  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.
  - shiroiuma 3y ago
    Anything involving a Carnot cycle is a rather primitive usage of energy, so I'm not surprised that turbines are close to their peak efficiency since humans have been using them for at least a century now. More modern forms of energy usage will skip the whole heat-cycle skip and just directly produce electricity from some other energy source. We're still in early stages of much of that; just look at how much PV (solar) efficiency has improved in the last few decades. And we've barely even looked at what we can do with nuclear power[1]. 1. https://en.wikipedia.org/wiki/Fission_fragment_reactor https://en.wikipedia.org/wiki/Fission_fragment_reactor
    - WJW 3y ago
      PV has increased from a <10% percent efficiency in the 80s to 25-30% now for commercially available panels. They can grow another 3.3x in efficiency at most, hardly comparable to the doubling every few years that semiconductors have had. The wikipedia link you provided contains the following snippet: > and can achieve efficiencies of up to 90% instead of 40-45% attainable by efficient turbine-driven thermal reactors. A doubling of efficiency is extremely nice, don't get me wrong. But after you get to 90% there is simply not much further to go. On the other hand, semiconductor production has probably not even reached 1% of what is achievable. Non-flat structures are still seen as incredibly advanced, let alone true 3D chip manufacturing. Bulk energy production will never see improvements comparable to those found in semiconductor manufacturing, simply because the systems don't have nearly as much "efficiency space" left to grow into.
NoMoreNicksLeft 3y ago
That's just a scaling issue.

DonnyV 3y ago

No warp drive, no artificial gravity. You really want to kill my morning. :-(

asah 3y ago
Wait until you hear about the situation in the middle east... :-(
- tomrod 3y ago
  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.
FridgeSeal 3y ago
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.
- DonnyV 3y ago
  "It’s like we got stuck on the “no fun” setting" Thats gold my friend. LOL
- charred_patina 3y ago
  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.
  - FridgeSeal 3y ago
    Yeah I’ve read the 3-body-problem books, didn’t enjoy them, but I’m well aware of the mechanic you’re speaking of.

davedx 3y ago

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 3y ago
The author addresses this (in a very condescending way) in the last couple paragraphs. But yes, I tend to agree with you.
- oldbbsnickname 3y ago
  It reminds me of NASA's EM Drive debacle from 2015.

phkahler 3y ago

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 3y ago

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.

elil17 3y ago
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 3y ago
  Hum, How can they be sure that what is hitting the plate is still antimatter? (Or only antimatter?)
  - ben_w 3y ago
    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.
3y ago

mr_mitm 3y ago

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 https://twitter.com/malcubierre/status/362011821277839360

marcosdumay 3y ago
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 3y ago
  >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
  - lawlessone 3y ago
    >The best you can do is drag the warp field behind your ship with normal thrusters. Ok we can build a warp trebuchet.
    - distract8901 3y ago
      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.

netbioserror 3y ago

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?

Filligree 3y ago
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.
Khoth 3y ago
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 3y ago
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 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_antimatter https://en.wikipedia.org/wiki/Gravitational_interaction_of_a... - -- [1] https://profmattstrassler.com/articles-and-posts/largehadroncolliderfaq/whats-a-proton-anyway/ 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/largehadroncolliderfaq/whats-a-proton-anyway/proton-collisions-vs-quarkgluonantiquark-mini-collisions/ https://profmattstrassler.com/articles-and-posts/largehadron...>)

jackcosgrove 3y ago

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.

zzzeek 3y ago
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 3y ago
  > 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 3y ago
    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.

gs17 3y ago

>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.

thsksbd 3y ago
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 3y ago
  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.
  - Izkata 3y ago
    > 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.
  - thsksbd 3y ago
    "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.
aetherson 3y ago
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 3y ago

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 3y ago
> 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.

pelorat 3y ago

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.

moomoo11 3y ago

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 3y ago
Where do you get the energy to move that amount of mass?
- Xymist 3y ago
  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.
- svachalek 3y ago
  Here's a proposal: https://www.youtube.com/watch?v=v3y8AIEX_dU https://www.youtube.com/watch?v=v3y8AIEX_dU

mst 3y ago

> our greatest science-fiction hope for achieving warp drive has completely evaporated Damnit, "was completely annihilated" was Right. There.

deafpolygon 3y ago

Looks like we're gonna have to bet on Spore drives.

timbit42 3y ago
What about jump drives in Battlestar Galactica?

pmarreck 3y ago

This has long been one of my justifications for the "maybe intelligent extraterrestrial pilot" theory of UFO's; now that theory is weakened...

distract8901 3y ago

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 3y ago
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.
- distract8901 3y ago
  >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
- empath-nirvana 3y ago
  But we've seen anti matter and we already _know_ it doesn't have negative mass.
jillesvangurp 3y ago
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.

mperham 3y ago

Quanta and BigThink are such great sites, pumping out high quality science journalism.

rilindo 3y ago
BigThink, ironically, is sponsored by the Charles Koch Foundation.
- WendyTheWillow 3y ago
  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/ https://bigthink.com/our-mission/ [1] https://www.crunchbase.com/organization/freethink-media/company_financials https://www.crunchbase.com/organization/freethink-media/comp... [2] https://www.linkedin.com/company/bedrockcap/ https://www.linkedin.com/company/bedrockcap/ [3] https://www.linkedin.com/company/mac-venture-capital/ https://www.linkedin.com/company/mac-venture-capital/
  - rilindo 3y ago
    It is on their web site: https://bigthink.com/people/charles-koch-foundation/ https://bigthink.com/people/charles-koch-foundation/
    - WendyTheWillow 3y ago
      That says nothing about sponsorship. At best, it implies a vague partnership, which is fundamentally different.

fabulous265 3y ago

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 3y ago
If its intention was to illustrate realistic causal disconnection, Interstellar does a pretty poor job. What with the causal loops and so on.
- outworlder 3y ago
  So you don't think it's realistic that 'love transcends dimensions of space and time'? :)
  - jameshart 3y ago
    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 3y ago
      > 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.

pnpnp 3y ago

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 3y ago
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?
- aldousd666 3y ago
  Antimatter was to be used to generate the energy required, by annihilation of regular matte, not the antigravity itself. "Exotic matter" is undefined as of yet in that it could still exist as something else. Some people are confusing the two ideas, even though some (few) people probably did actually think anywhere would anti-gravitate, as it were.

SkyMarshal 3y ago

> 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?

johnchristopher 3y ago
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".
Agathos 3y ago
"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).

jedberg 3y ago

It's ok, we still have 40 more years to figure it out.

ruined 3y ago
that's quite optimistic. i'd give us fifteen tops
- stevula 3y ago
  It's a reference to the year warp drive will be invented by Zefram Cochrane in the Star Trek universe.
nv2156 3y ago
Yeah once Dr Cochrane starts working on it :).
- jedberg 3y ago
  Give him a break, he isn't even born yet!
- WendyTheWillow 3y ago
  Maybe we should start naming every single person born as of now-ish, Zefram Cochrane, just to be safe...
  - qingcharles 3y ago
    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

deleted 3y ago

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OhNoNotAgain_99 3y ago

[dead]

lend000 3y ago

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 https://www.youtube.com/watch?v=b_Lre3B6SUQ

empath-nirvana 3y ago
Wouldn't it be more interesting to learn real physics instead of made up stuff?
- withinboredom 3y ago
  I enjoy fantasy physics more than regular physics by a pretty large margin.
- lend000 3y ago
  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.
  - 3y ago

qingcharles 3y ago

At this rate it is going to be easier to simply emulate the entire universe (aka Devs) and just travel virtually around space-time that way. Then we can just stay home and eat cheese puffs.

rpastuszak 3y ago
The universe is just a matryoshka of recursive couch potatoes eating cheese puffs.
- fsckboy 3y ago
  matryoshka's all the way down doesn't sound that great. OTOH, cheese puffs all the way down sounds pretty perfect.
- oldbbsnickname 3y ago
  Don't forget that we also only drink Mountain Dew Zero because water is yucky, and we have obligatory pet turtles with recursive acronym names.

aldousd666 3y ago

I'm glad they settled this one; however, to my knowledge nobody thought Anti-Matter meant "Anti-gravity" w/rt Alcubierre warp drive. That's not what they meant by 'exotic matter.' But ok. sure. There was doubt that exotic matter could exist at all, and nobody had doubts that anti-matter could exist. I think there is something lost in the translation here. (No I'm not saying that warp drive still must be possible, I just think people, including the article writers, are conflating things.)

MR4D 3y ago

We can focus light waves , sound waves, x-rays, etc. Why can’t we figure out how to focus gravity waves?

Frummy 3y ago
We can do a lot of stuff with energy in various forms but gravity is just from mass which is quite difficult to control. Essentially we suck at fission and fusion at meaningful scales and we have a very narrow capability as well. I mean, to destroy mass equivalent to Mars in a short time frame is a cosmically cataclysmic nuke, then to not waste that energy, so you efficiently capture it and recreate the mass elsewhere in one huge fusion reaction. Maybe I talked past you and just daydreamed about Dr Manhattan stuff, maybe what it takes to emit gravity at will at some location, is much more difficult than just redirecting it which I dont have the tools to daydream about.

ls612 3y ago

Doesn’t dark energy mathematically manifest as “negative mass”? Or am I misunderstanding what physicists mean by that?

omneity 3y ago

My understanding as a non-physicist is that the specific requirement for a warp bubble Alcubierre-style is negative mass. Now this negative mass is theorized to come from some form of exotic matter, which could but doesn’t have to be antimatter. The jury is still out on this one. As a fan of space travel, it seems the prospect of a warp drive is still not budging much from 0 chance. But that’s okay, we’re also not worse off where we started.

nirav72 3y ago

It seems that the limits of physics are itself the great filter.