Gravity Seems Holographic. What Does That Mean for Reality?

(quantamagazine.org)

51 points | by ibobev 3 hours ago

18 comments

  • haitchfivee 1 hour ago
    My nitpick is with something the author said in passing about Hawking. Yes, around 1970 Hawking and the scientific community at large still used to believe nothing could escape a black hole, and between 1971 and 1973 Hawking along with Penrose and others expanded their evolving understanding and consequences of of Albert Einstein's breakthrough work.

    But then Hawking argued back the opposite case, which in simple terms means that some things can, indeed, escape an event horizon. In fact, name dropping Hawking just to mention his views as they stood before his 1973 work, and his 1974 model of Hawking radiation seems dangerously incomplete journalistic reporting.

    In 1974 Hawking formulated what we now know as Hawking Radiation, which is the *exact opposite* of what was previously believed about the impossibility of anything coming back from a black hole. Whilst still not conclusively proven as a physical fact, this did win him the Special Fundamental Physics Prize in 2013. specifically for his discovery of Hawking radiation from black holes and his deep contributions to quantum gravity and quantum aspects of the early universe.

    • Maxatar 1 hour ago
      Not sure I follow your comment exactly, perhaps I am misunderstanding it but Hawking radiation doesn't involve anything escaping a black hole.

      The radiation never originates from within the event horizon. Furthermore the radiation itself does not encode any information about what fell into the black hole apart from the electric charge, angular momentum, and mass (all of which must remain conserved).

      • pixl97 1 hour ago
        The only caveat that I'd ask about is the death of a black hole after it evaporates away too much mass. If that explosion does occur, is that matter/energy that was from inside the singularity itself?
        • nine_k 48 minutes ago
          AFAICT nobody has a consistent theory proven by observations. Some theories offer an explosion in which the singularity vanishes, but this has trouble with information / entropy. Some say a microscopic remnant stops radiating because the original assumptions of Hawking radiation mechanism do not apply at near-Planck scale. Some say that as the curvature grows with the diameter shrinking, the black hole pops off from "our" spacetime and forms a parallel universe, without an explosion.

          The current age of the Universe is way small compared to the time needed for evaporation, so observing anything like that happening (or not) is hardly possible.

      • arcticfox 53 minutes ago
        I don't know the slightest about this but... That list looks like it is supposed to be limited but that sounds like infinitely more information than zero?
      • nine_k 1 hour ago
        Indeed All Hawking radiation takes from a black hole is some mass. It's a bit like radiation resulting from annihilation of matter and antimatter: it does not "escape", it "gets born" in the process.
      • empath75 54 minutes ago
        The entire blackhole will eventually evaporate, so yes it is literally escaping from the black hole.
    • glenstein 1 hour ago
      I find myself not agreeing with a lot of nitpicks, but this is a good one! The article says "Contrary to what Stephen Hawking argued, black holes are not inescapable prisons." But information escaping black holes is named after him! He definitely, in the full scope of his career, was perfectly agreeable to the idea of information escaping black holes.
      • parineum 54 minutes ago
        Those claims are backwards.

        Hawking found that energy/mass can escape but the information remains destroyed. You can't run a black hole backwards in time and reconstruct the matter that created it and hawking radiation bears no resemblance to anything that was ever beyond the horizon.

    • EA-3167 25 minutes ago
      You’re missing a big issue here… Hawking Radiation doesn’t escape from within the event horizon, and there’s no physical process preventing that. It’s radiation from the surface of the black hole, not the interior.
    • metalliqaz 1 hour ago
      Please correct my understanding as I am not a scientist, but why do you assert that Hawking radiation "escapes" or "comes out of" a black hole? Nothing crosses the event horizon. Isn't it more correct to say that Hawking radiation is produced by the extreme warping of the spacetime very near the event horizon, and the black hole shrinks to conserve the energy? Black holes can also shrink as gravitational waves are produced, but we don't say that the waves "escape" the black hole.
  • phailhaus 2 hours ago
    > Holography implies that you can do that — reconstruct every fold, vessel, and neuron in three dimensions — without actually looking inside. Simply photographing the surface of the brain somehow suffices.

    Gah I am not a fan of pop-sci simplifications like this for the sake of a soundbite. The author goes onto explain how no, a picture is not enough, you need to actually measure the distortion of spacetime at the surface. Somebody is going to walk away thinking this stuff is possible, that maybe psychics really can detect something wrong with them.

    • glenstein 1 hour ago
      I know what you mean and I think you're right, but I take it as the cost of doing business when trying to turn frontier physics into layperson analogies. You're not going to use an analogy to successfully complete a calculation of black hole entropy, you're going to use it to convey the high level intuition that "stuff on inside = stuff on boundary".

      Because if we litigate the imperfections of analogies all day long, then you're going to react to videos titled "black holes described at five levels of difficulty" by saying the first four levels were all wrong, which may in a sense be technically true but not in the spirit of the exercise.

      • phailhaus 33 minutes ago
        It's okay as long as they call it out, but the author doesn't and instead states it like a fact. They could have easily caveated it with "but a magical camera that can see magnetic and gravitational fields" or something. The analogy is fine, but it's not presented as one, so it's not clear how far the analogy actually goes. So the takeaway is "wow technically it's possible!"
    • groby_b 57 minutes ago
      It is Quanta, the home of sensationalist oversimplifcations. What did you expect, solid science?
      • phailhaus 35 minutes ago
        Yes, the rest of the article is pretty good.
  • VyseofArcadia 26 minutes ago
    Mathematician, not physicist, but it seems reasonable to me that you could encode a sufficiently constrained 3D space on a 2D boundary. And if you have such an encoding, it also doesn't seem insane that some things might be more easily modeled on the 2D boundary than the 3D space.

    If you can convert back and forth between a 2D representation and a 3D representation, and different phenomena are more easily modeled in each, does it matter which is "real"? Unless of course you can come up with a specific prediction and experiment to test it.

  • glenstein 2 hours ago
    As a non expert who's just curious about science but also tries to talk like a normal person, from what I can tell holography really seems like it's now the leading candidate to be the next big conceptual revolution in physics.

    There's not necessarily any breakthrough right around the corner and we shouldn't rush to coronation preemptively, but there's a lot of physics "voting with their feet" for holography as the article says, and I think it's officially time to start getting hyped. It could have sanity-restoring answers to questions of quantum weirdness, albeit at the rather expensive cost of giving up even more on our day to day intuitions about space and time in favor of an apparently informational substrate.

    String theory had a generation of great science communicators writing its books and singing its praises, but holography doesn't yet have equivalent public champions, and I hope that's something that changes sooner than later.

    • auntienomen 1 hour ago
      I don't think the distinction between holography and string theory is as clean as you're making it. The vague idea of holography predates string theory, but most of the working examples we have of holography come from string theory. That's what AdS/CFT is: It's an explicitly holographic description of superstring theory in an anti-Desitter space. It's frankly bizarre that the author of this article doesn't mention that fact. I suspect we are seeing a popular science rebranding of string theory without the word strings.
      • glenstein 1 hour ago
        I didn't intend to assert a clean distinction, you're exactly right about its connection to string theory. What I mean is that String Theory Writ Large enjoyed a lot of popular esteem in the 00s and 2010s in public communication as being our potential new framework for what lies beneath the quantum world, but string theory is huge in and of itself.

        It's more a difference of emphasis (holography in particular) than something that's outside the scope of string theory.

    • ck2 1 hour ago
      isn't holographic universe a similar concept to string theory in that they both propose higher dimensions projecting into lower dimensions

      string theory, 11 dimensions, is bonkers though, it's what happens when people are too smart for their own good imho lol

  • Sharlin 54 minutes ago
    > With gravity, mass plays the role of charge. It bends space-time around it, and it is always positive. There is no negative mass, so you can always infer the one real arrangement of stuff inside from the warping of space-time at the surface of your box.

    This is a simplification to the point of just being wrong. Gauss’s law works for gravity; if you put a shell around Earth you have no way of knowing whether it’s a planet or an Earth-mass black hole inside. Assuming spherical symmetry of density, anyway.

    • subtlepseudonym 31 minutes ago
      > This is a simplification to the point of just being wrong.

      Is it? If you project a "3D" singularity onto a surface, it's still a point. If you project a roughly spherical object, it's roughly circular.

      Gauss' law in this case would apply to the total force of gravity exerted by the mass within the shell, not its distribution across the surface of the shell.

  • zkmon 23 minutes ago
    If 3D space can be packed into a 2D hologram, then, can that 2D data be packed into a 1D hologram and so on?
  • tananaev 53 minutes ago
    I think the box explanation is misleading. There isn't literally a box whose surface you measure. The idea is that the state of a higher-dimensional gravitational system can, in some cases, be completely described by a theory in one fewer dimension.
  • jumploops 1 hour ago
    > “You can ‘compress all of the three-dimensional world into two dimensions.’”

    Would this imply that time is the third dimension?

    • stronglikedan 1 hour ago
      Wouldn't time be one of the two resulting dimensions - the other being space?
  • toddmorey 1 hour ago
    Aside: Quanta magazine always has excellent design & visuals.
  • hughw 1 hour ago
    When I read "But holography really starts to bite only after..." my LLM-dar goes off. Everything I read up to that point was comprehensible, but man, I have developed a shudder reaction to any language suggesting AI was involved ibn its creation.
    • burnte 1 hour ago
      I find AI written stuff to be hard to read. Part of my career is being a writer and I take great pride in my outout. AI written materials is a slog because you can see how it's pumping out words to hit various metrics rather than what's needed for the task.
  • ck2 1 hour ago
  • Razengan 1 hour ago
    <Layperson>

    Just as acceleration through space causes [the same effect as] gravity, could regular gravity be the movement through TIME?

    Could gravity be a facet of time as electricity is to magnetism and vice versa? and the reason we cannot "isolate" gravity is because it's interwoven with time?

    But then it would be weird that photos who don't experience time are affected by gravity..

    Or maybe space, time and gravity are a trinity?

    (no I'm not high, but maybe I should be)

    • condour75 1 hour ago
      is this why i increase in mass and volume every year?
      • Razengan 1 hour ago
        Do you also attract more things?
  • ltbarcly3 42 minutes ago
    This article seems to repeatedly blur the distinction between 'having space' to encode all the states inside a volume on it's surface and an actual theory of correspondence of states.

    "Having space" is just a consequence of black holes. If you have more information in a volume than can be encoded on its surface in theory, you have enough mass inside the volume to make it a black hole and the event horizon then has enough space to encode the information even if the original surface did not.

    The correspondence between information, thermodynamics, and mass that causes black holes to 'make it possible' to holographically encode all the information inside is what makes this theory so tempting. What if everything is information, and black holes aren't an expression of 'too much mass', but rather just a result of 'too much information to store'. This theory, if it existed, would demonstrate a key result of both relativity and quantum theory based on a very simple premise, and suggests it might then be possible to base both General Relativity and Quantum Theory on top of a simpler theory.

    > That’s a violation of logic and geometry. It asks us to erase the categorical difference between square meters and cubic meters.

    No, that's sheer nonsense.

    > There is no negative mass, so you can always infer the one real arrangement of stuff inside from the warping of space-time at the surface of your box.

    Positive mass does not make this argument work. Two bodies in GR can have different distributions of mass but identical exterior geometry. A counterexample is two spherically symmetric, uncharged bodies with the same total gravitational mass but different radial density profiles. By Birkhoff’s theorem, their exterior vacuum geometries are identical.

  • captainbadass33 1 hour ago
    [dead]
  • yepyoukno 2 hours ago
    Gravity is half spin hyperdimensional vector torsion. I have decided to accept “half spin torsion” as “vortex” and see gravity as the torsion interference along a G <timespace> dimensionality.

    There are other dimensionality!

    The dimensions are like origami, not parallel universes, however the relationships are as though such (all origami pieces then hyperdimensionality relate.)

    If we call the underlying “universal potential” and whatever we think our universe as, is a plane for hyperdimensional coordinates, much of this will begin to make sense.

    Gravity (and space time) is a “universal field” that “falls” Around the distributed mass (vector torsions of mass particles) and mass particles are universal potential (same stuff as measured energy in a photon) is half spin vector locked discrete amounts.

    Sub-atomic particles may then be discrete spin lock configurations and not distinct in any other way.

    This would make the Higgs particle a lie, and the Higgs field this deformation of gravitational surface area.

    Just what I’ve come up with. Existential reality (universal potential distributing) is holographic and gravity is half spin vector torsion on a plane of universal existence.

    • done_lurking 1 hour ago
      This is an interesting theory, but I think it has less explanatory power than the Sugon framework for gravity.
      • ltbarcly3 49 minutes ago
        This is not a theory.
        • done_lurking 25 minutes ago
          You are half spin torsioning my subatomic particles right now
    • Den_VR 2 hours ago
      What if you half spin the other direction?
      • pixl97 1 hour ago
        Like matter verses anti-matter? If so I think this has actually been considered by physicists hence we tested to ensure that anti-matter responds to gravity in the same way as matter.

        If anit-matter had shown anti-gravity effects then gravity may have been just some imbalance of forces in the universe, but it doesn't appear to be that way.

      • yepyoukno 1 hour ago
        Why would it matter?

        A torsion to the right, a torsion to the left mate in circular momentum.

        Sounds like complementary spins.

    • krapp 2 hours ago
      Physics threads on HN can be so entertaining.
      • copperx 2 hours ago
        Any HN thread where real thought is required devolves into insanity quickly.
      • yepyoukno 1 hour ago
        How is your pedophile America crusade going?

        Get to the bottom of who is running it all yet?

    • classified 1 hour ago
      > Sub-atomic particles may then be discrete spin lock configurations and not distinct in any other way.

      Using a spin lock is wasteful and not the best move in times of rising energy prices. Use a mutex to put the waiting thread to sleep.

      • yepyoukno 1 hour ago
        Spin lock traps potential, requiring more energy than available to release.

        That trapped potential in time and space is mass rather than radial propagation.

  • qsera 1 hour ago
    > space maybe an illusion..

    space is an illusion...The only thing that is absolute is consciousness, on top of which all illusions stand.

    • jjk7 58 minutes ago
      Consciousness is the greatest illusion of them all.
      • qsera 40 minutes ago
        Get a load of this. You can have only consciousness and still have a sensation of a full universe.

        Tell me again how Consciousness is an illusion..

    • psunavy03 58 minutes ago
      This doesn't make sense. Which consciousness is absolute? Yours or mine? Because I can't see your consciousness; I can only infer its existence. You can't see my consciousness; you can only infer its existence.
      • qsera 42 minutes ago
        >Yours or mine?

        Ours. Or every ones..We can easily accept that we inhabit the same spacetime. Why is it hard to imagine the same for consciousness?

    • captainbadass33 1 hour ago
      [dead]