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Is gravity just entropy rising? Long-shot idea gets another look
- john_moscow 1y agoSpace exists around things with mass. Also, above-absolute-zero temperatures cause particles to jump around randomly. Now if there is "more space" around particle A, particle B will have a slightly higher statistical chance of randomly jumping closer to it, than farther. Rinse-repeat. Gravity as we know it.
- enriquto 1y agoSounds fun! Would this imply that cold objects have weaker gravity?
- psittacus 1y agoIsn't this something we already know from the mass–energy equivalence? In the same way that a nuclear reaction that produces heat must cost the object mass (and therefore gravitational pull)
- Quarrel 1y agoIt does, but because you have to divide the energy change by c^2, it is really really hard to detect it, and mostly overwhelmed by other effects of the heating/cooling.
- enriquto 1y agowhy do the units matter here? Under this theory, will a body at absolute zero have no observable mass? No attractive field around it, no inertia if you try to move it.
- Quarrel 1y agoI'm only now seeing this a week later, but for E = mc^2, m is the rest mass. rest mass = all the energies of the mass, not just its thermal energy. So, as it approaches 0 kelvin the thermal energy approaches 0 and the mass approaches its minimal possible energy (its kinetic energy approaches zero), but even at absolute zero, it still has the rest-mass of its fundamental particles (electrons, neutrons and protons) which have mass inherently. In practice, the scale of the mass of the particles massively outweighs the scale of the thermal mass, so while strictly true, it mostly doesn't matter. So, because the scaling factor is stupid stupid large, changing temperature from anything to absolute zero does lower the mass, which does lower the gravity, but it just doesn't matter.
- Woansdei 1y agosounds more like the reverse to me, movement away from denser areas (less space), so like water leaking out of a container.
- bravesoul2 1y ago> particle B will have a slightly higher statistical chance of randomly jumping closer to it, Why? Also how do you explain acceleration due to gravity with that model. How do you explain solid objects?
- MaxikCZ 1y agoMy guess would be the answer is right in the part before you quote? If theres more "space" (imagining more space coordinates possible) for me on the left than on the right, me jumping to a random location would statistically move me left. Repeating results in movement, getting closer to the object intensifies this effect, results in acceleration. Solid objects are products of electric charge preventing atoms/particles from hitting each other, I dont think that has to have to do anything with gravity in this example?
- bravesoul2 1y agoI don't understand the more space thing then. Is this more space due to spacetime curvature or something else. E.g. if we have earth and moon: O o Why is there more space from the moon towards earth than away?
- jblezo 1y agoSpacetime curvature. Like if you dropped the earth on a giant sheet, it would stretch the sheet more than what the moon would have.
- bravesoul2 1y agoIf you rely on spacetime curvature for your explaination then why not just use general relativity to explain the gravity?
- JPLeRouzic 1y agoIt sounds a bit like Le Sage's theory of gravity: https://en.wikipedia.org/wiki/Georges-Louis_Le_Sage https://en.wikipedia.org/wiki/Georges-Louis_Le_Sage
- meindnoch 1y ago>Also, above-absolute-zero temperatures cause particles to jump around randomly. Does it? A single free particle won't "jump around randomly". Thermal motion is plain Newtonian motion with an extremely high rate of collisions. There's nothing random about it (let's put quantum things aside for now).
- AlexandrB 1y agoThis made me think of Norton's Dome[1] and how a particle would choose a direction to move when warmed from absolute zero to above absolute zero. Though I guess, "warming" in this context would mean a collision with another particle and that would determine the initial direction? [1] https://en.wikipedia.org/wiki/Norton%27s_dome https://en.wikipedia.org/wiki/Norton%27s_dome
- strogonoff 1y agoIf space existed around things with mass, then what would you call the emptiness that replaces space the further you go away from things with mass?
- dist-epoch 1y agoWe all know that life on Earth gets it's energy from the Sun. But we also know that's an approximation we tell kids, really life gets low entropy photons from the Sun, does it's thing, and then emits high entropy infrared waste heat. Energy is conserved, while entropy increases. But where did the Sun got it's low entropy photons to start with? From gravity, empty uniform space has low entropy, which got "scooped up" as the Sun formed. EDIT: not sure why this is downvoted, is the explanation Nobel Physics laureate Roger Penrose gives: https://g.co/gemini/share/bd9a55da02b6 https://g.co/gemini/share/bd9a55da02b6
- uncircle 1y agoYour question fascinated me. Googling "where did the Sun got its low entropy" I also came across these explanations: "Solar energy at Earth is low-entropy because all of it comes from a region of the sky with a diameter of half a degree of arc." also, from another reply: "Sunlight is low entropy because the sun is very hot. Entropy is essentially a measure of how spread out energy is. If you consider two systems with the same amount of thermal energy, then the one where that energy is more concentrated (low entropy) will be hotter." https://physics.stackexchange.com/questions/796434/why-does-sunlight-have-low-entropy https://physics.stackexchange.com/questions/796434/why-does-... Probably it's a bit of both. I'm not sure I understand your hypothesis about the Sun scooping up empty, low-entropy space. Wasn't it formed from dusts and gases created by previous stellar explosions, i.e. the polar opposite of low entropy?
- dist-epoch 1y agoI read the gravity explanation for the sun low entropy in the "Road to Reality" book from Roger Penrose. Asked Gemini to summarize the argument (scroll to end) https://g.co/gemini/share/bd9a55da02b6 https://g.co/gemini/share/bd9a55da02b6
- gattr 1y agoIt's also in his previous book "The Emperor's New Mind: Concerning Computers, Minds and The Laws of Physics", along with a lot more. Strongly recommended (even though after reading a lot of Greg Egan, my views on consciousness somewhat shifted towards "classical computation can do it, too".)
- MathMonkeyMan 1y agoEntropic gravity is a compelling framework. I think that most Physicists admit that it would be nice to believe that the yet unknown theory of everything is microscopic and quantum mechanical, and that the global and exquisitly weak force of gravity emerges from that theory as a sort of accounting error. But there are so many potential assumptions baked into these theories that it's hard to believe when they claim, "look, Einstein's field equations."
- mr_mitm 1y agoWhat are some of the most problematic assumptions in your opinion?
- nathan_compton 1y agoI'm not an expert in this field but I think reproducing realistic gravitational interactions seems to require a lot of fiddly set up with heat baths etc.
- quantadev 1y agoGravity doesn't interact, other than to simply set the shape of the spacetime in which particles move.
- nathan_compton 1y agoI think that might oversimplify things, in addition to being a model-laden description. There are empty-space solutions to GR (and indeed many a physicist has found the intuition that there is nothing but empty space appealing, cf geometrodynamics) and in these situations spacetime itself interacts with itself, no particles at all. In any case, I would say this is a somewhat bold description of what we know about gravity.
- quantadev 1y agoYou can disprove my statement by naming something gravity does other than add a shape to spacetime, if you want. Saying "I think you're probably wrong, but I just can't say why" is not an argument.
- omeysalvi 1y ago"There’s some kind of gas or some thermal system out there that we can’t see directly" - The Ether is back on the menu boys
- whycome 1y agoCaloric. Dark matter. Cosmological constant. We like placeholders for the unknown.
- jstanley 1y agoDon't forget phlogiston.
- holowoodman 1y agoVirtual Particles!
- bandrami 1y agoWas that de Broglie's thing? I always thought it didn't get a fair shake
- holowoodman 1y agoVirtual particles and related effects are actually widely accepted and experimentally proven (at least partially). Current physics wouldn't really work without them, or at least something that looks the same. https://en.wikipedia.org/wiki/Casimir_effect https://en.wikipedia.org/wiki/Casimir_effect https://en.wikipedia.org/wiki/Zero-point_energy https://en.wikipedia.org/wiki/Zero-point_energy https://en.wikipedia.org/wiki/Virtual_particle https://en.wikipedia.org/wiki/Virtual_particle https://en.wikipedia.org/wiki/Hawking_radiation https://en.wikipedia.org/wiki/Hawking_radiation The gist of it is, that quantum mechanics prevents vacuum from really being empty. Any finite-size system or any system with some kind of influence/force/anything will have a lowest energy state that is not actually zero energy but slightly above. Which means that this non-zero can fluctuate and on occasion pair-produce and pair-annihilate particles (probability inversely depending on pair energy). And yes, this sounds like some kind of ether...
- hoseja 1y agoLike some sort of buoyancy?
- meindnoch 1y agoI don't get it. To me, entropy is not a physical thing, but a measure of our imperfect knowledge about a system. We can only measure the bulk properties of matter, so we've made up a number to quantify how imperfect the bulk properties describe the true microscopic state of the system. But if we had the ability to zoom into the microscopic level, entropy would make no sense. So I don't see how gravity or any other fundamental physical interaction could follow from entropy. It's a made-up thing by humans.
- bmitc 1y ago> It's a made-up thing by humans. All of physics is made up by humans.
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- logicchains 1y agoEntropy isn't a function of imperfect knowledge. It's a function of the possible states of a system and their probability distributions. Quantum mechanics assumes, as the name implies, that reality at the smallest level can be quantised, so it's completely appropriate to apply entropy to describing things at the microscopic scale.
- kgwgk 1y ago> Entropy isn't a function of imperfect knowledge. It's a function of the possible states of a system and their probability distributions. There are no probability distributions over possible states when there is perfect knowledge of the state. > Quantum mechanics Entropy is also zero for a pure quantum state. You won’t have entropy without imperfect knowledge.
- whereismyacc 1y ago> There are no probability distributions over possible states when there is perfect knowledge of the state. I know very little about physics but I thought that the leading interpretations of quantum physics say that the probability distribution is all we can know about a system. The entropy is not due to due to a lack of information about the quantum state, but because the outcomes are inherently stochastic?
- metalman 1y agogravity=time
- evanb 1y agowhoa dude, that means gravity = money by transitivity. deep.
- the_sleaze_ 1y agoAnd that means gravity is the root of all evil. And what is a root? The bottom of something. Therefore gravity is the distilation of pure evil. This is proved by the question Could there be evil without gravity? Nope. And where do we find the most gravity? Yep. Black holes. Gravity is high entropy evil and Black holes are entrances to Hell.
- layer8 1y agoSo can we make hoverboards by losing money?
- pif 1y agoAs an experimental physicist, I refuse to get excited about a new theory until the proponent gets to an observable phenomenon that can fix the question.
- lewdwig 1y agoThe problem with emergent theories like this is that they _derive_ Newtonian gravity and General Relativity so it’s not clear there’s anything to test. If they are able to predict MOND without the need for an additional MOND field then they become falsifiable only insofar as MOND is.
- JPLeRouzic 1y agoPlease, how is the article related to MOND's theories?
- lewdwig 1y agoIn general, they’re not. But if the only thing emergent theories predict is Newtonian dynamics and General Relativity then that’s a big problem for falsifiability. But if they modify Newtonian dynamics in some way, then do we have something to test.
- westurner 1y agoFrom https://news.ycombinator.com/item?id=43738580 https://news.ycombinator.com/item?id=43738580 : > FWIU this Superfluid Quantum Gravity [SQG, or SQR Superfluid Quantum Relativity] rejects dark matter and/or negative mass in favor of supervaucuous supervacuum, but I don't think it attempts to predict other phases and interactions like Dark fluid theory? From https://news.ycombinator.com/item?id=43310933 https://news.ycombinator.com/item?id=43310933 re: second sound: > - [ ] Models fluidic attractor systems > - [ ] Models superfluids [BEC: Bose-Einstein Condensates] > - [ ] Models n-body gravity in fluidic systems > - [ ] Models retrocausality From https://news.ycombinator.com/context?id=38061551 https://news.ycombinator.com/context?id=38061551 : > A unified model must: differ from classical mechanics where observational results don't match classical predictions, describe superfluid 3Helium in a beaker, describe gravity in Bose-Einstein condensate superfluids , describe conductivity in superconductors and dielectrics, not introduce unoobserved "annihilation", explain how helicopters have lift, describe quantum locking, describe paths through fluids and gravity, predict n-body gravity experiments on earth in fluids with Bernoulli's and in space, [...] > What else must a unified model of gravity and other forces predict with low error?
- brador 1y agoAnti matter is created and repulsed and expelled, leaving a vacuum, things get sucked into that vacuum, creating the illusion of gravity, that’s my novel theory.
- IAmBroom 1y agoVacuums don't suck; high pressure repels. Similarly, umbrellas aren't places to stand under when it's not raining.
- cwharris 1y agoThis seems backwards. Entropy is a dispersive force — it favors distribution and disorder. But the universe clumps. Planets, stars, galaxies — all of them are low-entropy configurations. So how did scattered dust particles form the planet we’re standing on… through entropy? If gravity is just emergent from entropy, then it should be fighting against planet formation, not causing it. There’s a missing piece here — maybe coherence, resonance, or field attraction. But “just entropy”? That doesn’t explain formation. It explains dissolution.
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- konschubert 1y agoThis is not a philosophical discussion
- cwharris 1y agoThis paper is literally physical philosophy. To be science, it would require recursive experimentation, observation, and adjustment to hypothesis, until the model it proposes becomes a stable, reliable, and (most importantly) useful interpretation. It does none of that, and so I have no responsibility to do so prior to discussing it.
- heyjamesknight 1y agoEntropy isn't a force. It doesn't "favor" anything. Its a property of statistics, information, and distributions. Also why does this have that particular ChatGPT social media post rhythm to it? Please, Lord, tell me we haven't reached the point where people are writing HN comments w/ AI.
- bee_rider 1y agoWe’ve definitely reached that point. I’ve seen responses that are essentially, Well, here’s what ChatGPt has to say: <begin massive quote> If folks are doing that, then I assume they are also quoting it without citation—although, I have no idea about this case. It looks sort of rambling for ChatGPT, doesn’t it?
- neuroelectron 1y agoThe speed of light is C, a constant. Mass is composed of these particles that are bound by C. Because they are vibrating, a lot of that speed is being wasted in brownian motion. So the denser it is, the more your average vector is going to be toward more dense brownian motion as the particles interact and induce more brownian motion. The gradient has a natural sorting effect. Seems pretty intuitive to me. The question remains though, what is this density made of since gravity exists in a vacuum? Quantum fluctuations popping in and out of reality? Does this infer that quantum fluctuations are affected by mass as well? It would seem so since in Bose Einstein Condensate, what is "communicating" the state across the BEC if the particles are no longer interacting?
- ajkjk 1y agoDoesn't sound intuitive at all really...
- neuroelectron 1y agoYou can see it in action with a simple random walk program. Allow the steps to decrease in size toward one side of the screen and they will statistically be sorted toward the shorter steps.
- steamrolled 1y ago> Because they are vibrating, a lot of that energy is being wasted in brownian motion. So the denser it is, the more your average vector is going to be toward more dense brownian motion as the particles interact and induce more brownian motion ... Seems pretty intuitive to me. So this is why warm objects weigh more?
- parineum 1y agoThis reads like a sarcastic quip so, sorry if it wasn't but, they do. Solve for m in E=mc^2 and see what happens when objects have more energy.
- deleted 1y ago
- Caelus9 1y agoIt's a fascinating idea that gravity could be an emergent result of how information works in the universe. I feel like we still don't have that clear piece of evidence where this model predicts something different from general relativity. For now it is one of those theories that are fun to explore but still hard to fully accept.
- deadbabe 1y agoCouldn’t it be a byproduct of frame dragging? Any massive object that spins is pulling stuff into it by forcing things to rotate in some kind of space time whirlpool? This means if something massive doesn’t spin, it would have no gravity, but isn’t everything large enough to have gravity in space pretty much spinning?
- nathias 1y agoDescartes had a similar idea, but as far as I remember, it requires ether.
- ang_cire 1y agoNo, many asteroids have detectable, "functional" (e.g. they pull dust towards them) gravitational fields, but are not spinning like planets.
- vkou 1y agoGiven that we can experimentally observe the gravitational attraction between two non-spinning objects in a lab, I don't think that's the answer.
- abetusk 1y agoEntropic gravity is like the "brazil nut effect" [0] [1]. The idea is that if you shake a glass full of different sized nuts, the large ones will rise to the top. From what I understand, this is because larger objects have more mass, moving slower when shaked, so as the larger (brazil nuts) don't move as much relative to the smaller ones (peanuts), and because of gravity, there's a cavity left under the brazil nut which gets filled in with peanuts. For entropic gravity, the idea is that there's a base density of something (particles? sub-atomic particles?) hitting objects in random ways from all directions. When two large massive objects get near each other, their middle region will have lower density thus being attracted to each other from particles hit with less frequency from the lower density region. They sort of cast a "shadow". I'm no physicist but last time I looked into it there were assumptions about the density of whatever particle was "hitting" larger massive objects and that density was hard to justify. Would love to hear about someone more knowledgeable than myself that can correct or enlighten me. As an aside, the brazil nut effect is a very real effect. To get the raisins, you shake the raisin bran. To get gifts left from your cat, you shake the kitty litter. It works surprisingly well. [0] https://en.wikipedia.org/wiki/Granular_convection https://en.wikipedia.org/wiki/Granular_convection [1] https://www.youtube.com/watch?v=Incnv2CfGGM https://www.youtube.com/watch?v=Incnv2CfGGM
- sim7c00 1y agobut these nuts move by gravity do they not? and what in the universe is exactly up and down? and why would that matter? are all celestial bodies then a local up and 'away from them' down? this analogy hurts my brain. please tell me how to make the hurting stop
- jvanderbot 1y agoYou need to reread the middle only. It's a kind of "vacuum" effect.
- sim7c00 1y agobut where in nature is then this vacuum? is it just higher and lower energy density or something? like high and low pressure systems in weather pushing and pulling? that would or might imply gravity is electromagnetic? (sorry if this seems really off the charts / missing your point!)
- fourthark 1y ago> "The ontology of all of this is nebulous"
- amai 1y agoSo entropy can curve spacetime? My fridge locally lowers entropy, does that mean inside my fridge gravity is lower than outside?
- raindeer2 1y agoWonder if this perspective is compatible with Wolframs physics model based on hypergraphs? Gravity, in this framework, is an emergent property arising from the statistical behavior of the hypergraph's evolution, suggesting that gravity is an "entropic force" arising from the tendency of the system to minimize its computational complexity
- colanderman 1y agoSee also: emergent fox-treasure gravity in Skyrim: https://www.eurogamer.net/skyrims-myth-of-the-treasure-fox-finally-explained https://www.eurogamer.net/skyrims-myth-of-the-treasure-fox-f... TLDR: areas around treasure have higher entropy by a measure relevant primarily to stochastic movement of foxes. Since there are thus on average more ways for a fox to walk toward treasure than away, they tend to gravitate toward treasure.
- bawana 1y agothe statistical mechanical definition of entropy relies on the number of possible arrangements of particles in a system. In a closed system entropy approaches an equilibrium which has been sensationally described as the 'heat death of the universe'. But since we know our universe is expanding, the number of possible arrangements is also increasing so entropy may never reach equilibrium. If the universe is expanding faster than its components redistribute, then entropy could be decreasing. With this in mind, any theory involving entropy as a component of gravity would suggest a changing gravity over time
- almosthere 1y agoI think it's magnetism. Been saying this for years. Mostly non-aligned fields, the net effect leans just slightly towards a pull.
- fnordpiglet 1y agoI’ve been a believer in entropic gravity for a long time and believe it’s due to quantum foam. In a region of space with nothing in it the quantum foam in that space would be perfectly uniformly random. With mass and energy the state of the space would be biased and less random. This creates an entropic gradient. Further this doesn’t just explain gravity but explains why the space between galaxies seems to demonstrate negative energy and space expansion. I’m glad to see more research into the idea of entropic gravity as it’s IMO a more reasonable explanation than most other gravity theories I’ve heard.
- MintNow 1y agonice product
- the__alchemist 1y agoThis effect reminds me of the "hydrophobic interactions" used when modelling biological systems. E.g. The tendency for hydrophobic residudes to be on the inside of a protein.
- uticus 1y agoreally enjoyed this article from a few years ago. looks like the domain is no longer active but the content is a good intro and most of the external links still work https://web.archive.org/web/20211215122133/https://an0maly.co/why-is-gravity-so-strange/ https://web.archive.org/web/20211215122133/https://an0maly.c...