[HN Gopher] Is gravity just entropy rising? Long-shot idea gets ...
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Is gravity just entropy rising? Long-shot idea gets another look
Author : pseudolus
Score : 242 points
Date : 2025-06-16 00:36 UTC (22 hours ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| john_moscow wrote:
| Space 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 wrote:
| Sounds fun!
|
| Would this imply that cold objects have weaker gravity?
| psittacus wrote:
| Isn'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 wrote:
| It 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 wrote:
| why 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.
| bravesoul2 wrote:
| > 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 wrote:
| My 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 wrote:
| I 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 wrote:
| Spacetime curvature.
|
| Like if you dropped the earth on a giant sheet, it would
| stretch the sheet more than what the moon would have.
| bravesoul2 wrote:
| If you rely on spacetime curvature for your explaination
| then why not just use general relativity to explain the
| gravity?
| Woansdei wrote:
| sounds more like the reverse to me, movement away from denser
| areas (less space), so like water leaking out of a container.
| JPLeRouzic wrote:
| It sounds a bit like Le Sage's theory of gravity:
|
| https://en.wikipedia.org/wiki/Georges-Louis_Le_Sage
| meindnoch wrote:
| >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 wrote:
| This 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
| strogonoff wrote:
| If 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 wrote:
| We 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
| uncircle wrote:
| Your 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-...
|
| 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 wrote:
| I 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
| gattr wrote:
| It'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".)
| eru wrote:
| Yes, the main argument in the Emperor's New Mind seems to
| boil down to 'consciousness is weird, and quantum stuff
| is weird, so consciousness needs to be quantum'.
|
| If you can look past that, there's some good other
| material inside.
| im3w1l wrote:
| The universe was low entropy at the time of the big bang, and
| even though entropy is steadily rising, the universe is still
| pretty low entropy.
| mjanx123 wrote:
| The photons do not have entropy.
|
| The photons from Sun are hot, the space around Sun is cold, the
| system has a low entropy.
|
| If the space around Sun was as hot as the photons, the entropy
| would be high.
| aurareturn wrote:
| 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.
|
| From the Big Bang originally. We don't know what caused the Big
| Bang.
| gavinray wrote:
| The end of the previous Big Bang, a-la Big Bounce ;^)
|
| "It's turtles all the way down."
| riskable wrote:
| Based on the theory of gravity in the article it's
| actually, "Archimedes Principle all the way down."
|
| https://en.wikipedia.org/wiki/Archimedes%27_principle
| jerf wrote:
| One of the major challenges with "Big Bounce" that media
| coverage of it tends to overlook is that it is not entirely
| clear how the previous universe, which is presumably high
| entropy if it's supposed to be like ours, becomes the low
| entropy feedstock for the next universe. There's still a
| "And Here There Be Magic" step there.
|
| I'm not saying there's no solution; indeed, this is the
| sort of thing where the problem is that the profusion of
| proposed solutions is exactly the thing that shows there's
| a problem there. I think people tend to intuitively think
| that "lots and lots of possible solutions" is somehow
| better than "no solutions at all" but they're actually
| nearly the same thing.
| layer8 wrote:
| You'd have to explain how the steadily increasing entropy
| in our universe would revert to a low-entropy state again.
| dawnofdusk wrote:
| This is just a question about the origins of inhomogeneity in
| the universe. The prevailing theory is cosmic inflation, I
| believe: in the early universe a quantum field existed in a
| high entropy state and then the rapid expansion of space
| magnified small spatial inhomogeneities in the field into
| large-scale structures. What we see as "low entropy" structures
| like stars are actually just high entropy, uniform structures
| at a higher scale but viewed from up close so that we can see
| finer-scale structure.
| MathMonkeyMan wrote:
| Entropic 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 wrote:
| What are some of the most problematic assumptions in your
| opinion?
| nathan_compton wrote:
| I'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.
| gus_massa wrote:
| > _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,_
|
| I agree.
|
| > _and that the global and exquisitly weak force of gravity
| emerges from that theory as a sort of accounting error._
|
| Nah, it's probably just another weird family of bosons, just
| like the other forces.
|
| From the article:
|
| > _Entropic gravity is very much a minority view. But it's one
| that won't die, and even detractors are loath to dismiss it
| altogether._
| evanb wrote:
| Jacobson showed that thermodynamics + special relativity = GR.
| Those are very very general assumptions, so general that it's
| hard to even consider what else you might ask for.
| cryptonector wrote:
| Ooh, link?
| evanb wrote:
| https://arxiv.org/abs/gr-qc/9504004
| cryptonector wrote:
| Thank you!
| andyferris wrote:
| Interesting!
|
| > This perspective suggests that it may be no more
| appropriate to canonically quantize the Einstein equation
| than it would be to quantize the wave equation for sound
| in air.
|
| This seems like an odd sentence - what about phonons?
| layer8 wrote:
| From the article, they don't claim Einstein's field equations
| yet, just classical Newtonian gravity, at present.
| omeysalvi wrote:
| "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 wrote:
| Caloric. Dark matter. Cosmological constant.
|
| We like placeholders for the unknown.
| jstanley wrote:
| Don't forget phlogiston.
| holowoodman wrote:
| Virtual Particles!
| bandrami wrote:
| Was that de Broglie's thing? I always thought it didn't
| get a fair shake
| holowoodman wrote:
| Virtual 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/Zero-point_energy
|
| https://en.wikipedia.org/wiki/Virtual_particle
|
| 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...
| tsimionescu wrote:
| The Wikipedia article that you quote is quite explicit
| that, while virtual particles are a widely accepted
| mathematical tool, they're actual existence of elements
| of reality is very much not widely accepted, and
| definitely nowhere close to "experimentally verified".
| It's in fact considered impossible to verify
| experimentally, even in principle.
|
| Note that there are many very widely used physical
| theories that include mathematical elements that are not
| necessarily assigned any physical meaning. The Poynting
| vector in classical electrodynamics, for example, carries
| no widely accepted physical meaning, even though it
| appears in many well verified and used calculations. This
| doesn't make the theory suspect or anything, I'm not
| trying to imply that - simply that virtual particles
| being "real" or not is a mostly philosophical question
| that has no widely accepted consensus.
| holowoodman wrote:
| Those particles are virtual in that they don't really
| exist, so you are right that proving them isn't actually
| possible, because they are simply not there, just
| virtually, in our mathematical imagination. In quantum
| mechanics[1], this isn't really a "doesn't exist" kind of
| thing, rather it means that the wave function is there,
| leading to the (slim) possibility of existence through
| some kind of wave function collapse.
|
| What is proven is that e.g. vacuum energy / zero point
| energy exists (not actually in the StarGate sense of
| extractable energy, just that the lowest energy state of
| any physical system isn't zero), and that the Casimir
| effect exists. Vacuum energy directly leads to virtual
| particles through pair production (which is a proven
| mechanism, at high energies, for low energies we do
| suspect that there isn't a cutoff there), and also
| influences e.g. high-energy cosmic rays leading to an
| observed high-energy cutoff (although there are other
| possible explanations for that cutoff and lack of very-
| high-energy cosmic rays). The Casimir effect is most
| easily explained by virtual particles and vaccum energy.
|
| In Hawking radiation, the idea is actually that virtual
| particles through interaction with the gravity of the
| black hole become real particles. The event horizon
| actually makes those wave functions collapse such that
| real particles start to exist. Hawking radiation hasn't
| been observed yet, however.
|
| [1] non-Kopenhagen QM has the same consequences, it's
| just even harder to explain actually.
| griffzhowl wrote:
| You're probably thinking of the de Broglie-Bohm pilot
| wave theory, where there are actual particles with
| determinate trajectories at all times, which are
| probabilistically guided by a wave. I think they main
| problem with this idea is that it can't be made
| relativistically invariant, and so it can only be used
| for systems with low realtive velocities of its
| components.
|
| OTOH de Broglie for one of the central ideas in the
| development of quantum mechanics: he inverted Einstein's
| idea about photons, which were previously thought to be
| waves but Einstein showed how they came in particle-like
| quanta. de Broglie realised you could apply the same
| thinking to matter, which had previously been thought of
| as particles, and describe them using waves. Subsequent
| observation of wavelike dynamics (diffraction) of
| electrons in the Davisson-Germer experiment got de
| Broglie the Nobel prize.
| killerstorm wrote:
| Isn't that how equations get solved?
|
| Pretty much anything known entered through such placeholder,
| it's just that equations could be connected more easily.
|
| It's not like Higgs field is something you can directly
| observe
| jstanley wrote:
| Maybe, (I don't know), but it's easy to accidentally come
| up with a theory of "mysterious stuff" that appears to
| explain something, but neither constrains your expectation
| nor provides predictions.
|
| Phlogiston is the classic example.
| https://www.lesswrong.com/posts/RgkqLqkg8vLhsYpfh/fake-
| causa...
| FrustratedMonky wrote:
| Its a process.
|
| You find some un-identified variables.
|
| Form some hypothesis, try to narrow it down.
|
| Sometimes it is a discovery, new particle, and sometimes
| it is nothing.
|
| But that is how science works.
|
| At some point in time, everything was an unknown, and
| people had to work with unknowns.
|
| This whole movement from the 'right' that all science has
| to know the answers ahead of time in order to justify
| spending money, is hindering progress. How can you know
| the results are worthwhile, in order to justify funding,
| before doing the research to know the results?
| mr_toad wrote:
| The Phlogiston theory made one crucial prediction - that
| the speed of light would vary depending on the observer's
| movement through the ether. That prediction turned out to
| be famously wrong.
| Keyframe wrote:
| Right, but you can push unknowns into tmp vars only so much
| before you have to introduce constraints, otherwise it's
| all downright undetermined. You have to inject a structure
| into the placeholder soup or you're just pushing ambiguity
| around with no real net gain.. which is also fun to play
| around, question is will you get a paper out of it or even
| paid if you play like that to no end.
| RGamma wrote:
| Primordial black holes.
| grumbelbart2 wrote:
| It has been back for a while in the form of quantum fields.
| cantor_S_drug wrote:
| What Causes Gravitational Time Dilation? A Physical
| Explanation.
|
| https://www.youtube.com/watch?v=DjwQsKMh2v8
|
| I like the river model which helps with the intuition.
| ThinkBeat wrote:
| 95% of the Universe is made up of dark matter and dark energy.
| These are words astronomers have come up with to give a name to
| the mysterious, invisible side of the Universe
| hoseja wrote:
| Like some sort of buoyancy?
| meindnoch wrote:
| I 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.
| logicchains wrote:
| Entropy 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 wrote:
| > 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 wrote:
| > 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?
| kgwgk wrote:
| Entropy is about the state - not about "outcomes".
|
| "All we can know" is the precise state - at least in
| principle - and entropy is zero in that case.
| mr_mitm wrote:
| Just look at the definition of entropy. Knowledge about a
| system never enters the equation.
|
| S := -k_B sum p_i ln (p_i)
| kgwgk wrote:
| p_i
|
| Edit to add lots of words:
|
| In the definition of entropy
|
| S := -k_B sum p_i ln (p_i)
|
| knowledge about the system enters the equation in the p_i
| terms.
|
| The other term is a constant so it's not like there are
| many other choices to link the entropy to the system!
| mr_mitm wrote:
| Please communicate in full sentences with me.
|
| I can only guess that your objection is something about
| probabilities. A microstate has a probability independent
| of my knowledge of the system just like the probability
| of having a royal flush doesn't change after drawing five
| cards. The probability of _me ending the game_ with a
| royal flush might, but that is not what we mean by these
| probabilities.
| kgwgk wrote:
| The same microstate will have different probabilities
| depending on what are the constraints or measurements
| used in _your_ description of the system.
|
| If you choose to describe the system using its microstate
| - and you know it - there are no probabilities anywhere.
|
| You can of course know something and choose to ignore it
| - the entropy is still a reflection of the uncertainty
| (actual or for the sake of a lower-resolution model).
| tsimionescu wrote:
| But the point is that, regardless of how you choose to
| describe or even measure the system, it will need exactly
| as much heat to raise its temperature by 1 degree (or it
| will need as much kinetic energy to increase the average
| velocity of the constituents by the same amount, in the
| microstate framework). So there is some objective nature
| to entropy, it's not merely a function of subjective
| knowledge of a system. Or, to put it another way, two
| observers with different amounts of information on the
| microstate of a system will still measure it as having
| the same entropy.
| kgwgk wrote:
| There is some objective nature to the operational
| definition of entropy based on an experimental setup
| where you fix the volume and measure the temperature or
| whatever.
|
| And this is related to the statistical mechanical
| definition of entropy based on the value of the
| corresponding state variables.
|
| But it's not a property of the microstate - it's a
| property of the macrostate which makes sense only in the
| context of the experimental constraints and measurements.
|
| If we relate entropy to work that can be extracted
| someone with a better understanding of the state of the
| system and operational access to additional degrees of
| freedom can extract additional work.
|
| Thermodynamics assumes the state variables provide a
| complete description of the system. Statistical mechanics
| assumes the state variables provide an incomplete
| description of the system - and work out what that
| entails.
| tsimionescu wrote:
| > But it's not a property of the microstate - it's a
| property of the macrostate which makes sense only in the
| context of the experimental constraints and measurements.
|
| The same can be said about the wavefunction then, right?
| You can't directly observe it, you can only use it to
| predict the statistics of a particular experimental
| setup. So, at worse, entropy is as real as wavefunction
| amplitudes.
|
| > If we relate entropy to work that can be extracted
| someone with a better understanding of the state of the
| system and operational access to additional degrees of
| freedom can extract additional work.
|
| Is this actually true? Per my understanding, if I give
| you three containers, two of which are filled with some
| kind of gas that you know nothing about, and the third
| with a mix of those same gases, you can measure their
| entropy using thermodynamic experiments and tell which of
| the three is a mix of the other two because it will have
| a higher entropy. So, you can extract more work from one
| of the boxes despite not knowing anything more about it.
| kgwgk wrote:
| > Per my understanding
|
| What's the source of that understanding? You cannot
| measure the entropy, only changes of entropy - which will
| be the same (for an ideal gas).
|
| Edit: we already had this discussion, by the way:
| https://news.ycombinator.com/item?id=42434862
| tsimionescu wrote:
| > You cannot measure the entropy, only changes of entropy
|
| You can measure the changes in entropy from a minimal
| state and integrate - and you'll get the "total" entropy.
|
| And thanks for looking it up! I remembered a very similar
| conversation and was wondering if you were the same
| person, but was a bit lazy to search :)
| kgwgk wrote:
| > You can measure the changes in entropy from a minimal
| state and integrate - and you'll get the "total" entropy
|
| That doesn't help with the following (at least if you
| keep those kinds of gas in gas state):
|
| > if I give you three containers [...] you can measure
| their entropy using thermodynamic experiments and tell
| which of the three is a mix of the other two because it
| will have a higher entropy
|
| But you can weight them, it's much easier.
| ajkjk wrote:
| As the other replier said, despite your dismissiveness,
| the knowledge about the system is in the probabilities,
| so it's right there in the equation.
|
| Suppose you flip a coin. Before flipping the coin, your
| knowledge is "heads or tails". After flipping it, your
| knowledge becomes one of either heads or tails. The
| amount of information you gained by resolving your
| imperfect knowledge is the entropy of the distribution.
|
| The same model works for physical entropy without much
| modification; the imperfect knowledge is the difference
| between knowing a macrostate versus the exact microstate.
| antonvs wrote:
| You're glossing over an important point: your knowledge
| of the _future_ state of the system is "heads or tails".
|
| One of the things entropy tells us how a system is likely
| to evolve in future. But looking at this another way,
| entropy actually helps dictate how it will evolve in
| future. And we can prove that mathematically.
| aurareturn wrote:
| If we knew the exact state of all particles in an enclosed
| system, we can calculate what future states will be exactly.
| No need to calculate possible states.
| IAmBroom wrote:
| Since that's not possible in any physical system of one or
| more particles, it's irrelevant.
| mensetmanusman wrote:
| Quantum uncertainty actually says no to this. There is an
| 'error' in any propagating probability field.
| willvarfar wrote:
| The way we use the word 'entropy' in computer science is
| different from how its used in physics. Here is a really good
| explanation in a great talk! https://youtu.be/Kr_S-
| vXdu_I?si=1uNF2g9OhtlMAS-G&t=2213
| antonvs wrote:
| Your perspective is incorrect.
|
| Physical entropy governs real physical processes. Simple
| example: why ice melts in a warm room. More subtle example: why
| cords get tangled up over time.
|
| Our measures of entropy can be seen as a way of summarizing, at
| a macro level, the state of a system such as that warm room
| containing ice, or a tangle of cables, but the measure is not
| the same thing as the phenomenon it describes.
|
| Boltzmann's approach to entropy makes the second law pretty
| intuitive: there are far more ways for a system to be
| disordered than ordered, so over time it tends towards higher
| entropy. That's why ice melts in a warm room.
| refactor_master wrote:
| I think original post is confused exactly because of "tangled
| chords" analogies. Something being "messy" in our daily lives
| can be a bit subjective, so using the same analogies for
| natural forces may seem a tad counterintuitive actually.
|
| Maybe it would be more fitting to say that it just so happens
| that our human definition of "messy" aligns with entropy, and
| not that someone decided what messy atoms look like.
|
| I'd say a bucket of water is more neat than a bucket of ice,
| macroscopically.
| HelloNurse wrote:
| But "disordered" and "ordered" states are just what we define
| them to be: for example, cords are "tangled" only because we
| would prefer arrangements of cords with less knots, and knots
| form because someone didn't handle the cords carefully.
|
| Physical processes are "real", but entropy is a figment.
| dekken_ wrote:
| I believe you are correct.
|
| Entropy is not a physical quantity, it is a measure of how
| far a system is from equilibrium.
|
| Lots of people talk about order/disorder or macro and micro
| states, not realizing these are things we've invented and
| aren't physical in nature.
| kgwgk wrote:
| > Entropy is not a physical quantity, it is a measure of
| how far a system is from equilibrium.
|
| That's funny because the original thermodynamic entropy
| is defined only for systems in equilibrium.
| dekken_ wrote:
| from who? Clausius?
|
| It doesn't make a lot of sense to me because a system at
| equilibrium, cannot go undergo any further diffusion, so
| there's no potential "entropy increase"
|
| Maybe the issue, is that, like an ideal gas, a perfect
| equilibrium just doesn't occur.
| ludwik wrote:
| > there are far more ways for a system to be disordered than
| ordered
|
| I'm a complete layman when it comes to physics, so forgive me
| if this is naive -- but aren't "ordered" and "disordered"
| concepts tied to human perception or cognition? It always
| seemed to me that we call something "ordered" when we can
| find a pattern in it, and "disordered" when we can't.
| Different people or cultures might be able to recognize
| patterns in different states. So while I agree that "there
| are more ways for a system to be disordered than ordered," I
| would have thought that's a property of how humans perceive
| the world, not necessarily a fundamental truth about the
| universe
| hackinthebochs wrote:
| Think minimum description length. Low entropy states
| require fewer terms to fully describe than high entropy
| states. This is an objective property of the system.
| amelius wrote:
| In a deterministic system you can just use the time as a
| way to describe a state, if you started from a known
| state.
| sat_solver wrote:
| You're thinking of information entropy, which is not the
| same concept as entropy in physics. An ice cube in a warm
| room can be described using a minimum description length
| as "ice cube in a warm room" (or a crystal structure
| inside a fluid space), but if you wait until the heat
| death of the universe, you just have "a warm room" (a
| smooth fluid space), which will have an even shorter mdl.
| Von Neuman should never have repurposed the term entropy
| from physics. Entropy confuses a lot of people, including
| me.
| nick__m wrote:
| And somewhat surprisingly the heat death of the universe
| is the maximal entropy state.
|
| Because there are an infinite number of microstates (all
| the particles are interchangeable) that lead to the same
| macrostate: nothing happening for ever!
| hackinthebochs wrote:
| Maxwell's demon thought experiment implies they are the
| same concept. Given a complete knowledge of every
| particle of gas you can in principle create unphysical
| low entropy distributions of the particles. This[1] goes
| into more detail.
|
| [1] https://en.wikipedia.org/wiki/Entropy_in_thermodynami
| cs_and_...
| bavell wrote:
| A fun visual explanation:
| https://youtu.be/8Uilw9t-syQ?si=D9sR2YAm40SPFG3a
| zmgsabst wrote:
| "Number of terms" is a human language construct.
| hackinthebochs wrote:
| No, it's a representation construct, i.e. how to describe
| some system in a given basis. The basis can be
| mathematical. Fourier coefficients for example.
| zmgsabst wrote:
| Mathematics is a human language. It being a formal
| language doesn't change that.
|
| Further, it's not objective: you're choosing the basis
| which causes the complexity, but any particular structure
| can be made simple in some basis.
| hackinthebochs wrote:
| Mathematical notation is a human invention, but the
| structure that mathematics describes is objective. The
| choice of basis changes the absolute number of terms, but
| the relative magnitude of terms for a more or less
| disordered state is generally fixed outside of degenerate
| cases.
| zmgsabst wrote:
| The structure that most words describe is objective, so
| you haven't distinguished math as a language. (Nor is
| mathematics entirely "objective", eg, axiom of choice.)
| And the number of terms in your chosen language with your
| chosen basis isn't objective: that's an intrinsic fact to
| your frame.
|
| The complexity of terms is not fixed -- that's simply
| wrong mathematically. They're dependent on our chosen
| basis. Your definition is circular, in that you're
| implicitly defining "non-degenerate" as those which make
| your claim true.
|
| You can't make the whole class simplified at once, but
| for any state, there exists a basis in which it is
| simple.
| hackinthebochs wrote:
| This is getting tedious. The point about mathematics was
| simply that it carries and objectivity that natural
| language does not carry. But the point about natural
| language was always a red-herring; not sure why you
| introduced it.
|
| >You can't make the whole class simplified at once
|
| Yes, this is literally my point. The further point is
| that the relative complexities of two systems will not
| switch orders regardless of basis, except perhaps in
| degenerate cases. There is no "absolute" complexity, so
| your other points aren't relevant.
| mr_mitm wrote:
| You only hear these terms in layman explanations. Physics
| has precise definitions for these things. When we say
| "ordered", we mean that a particular macrostate has only
| few possible microstates.
|
| Check this Wikipedia article for a quick overview: https://
| en.wikipedia.org/wiki/Microstate_(statistical_mechan...
|
| Details can be found in any textbook on statistical
| mechanics.
| Gravityloss wrote:
| Exactly. The coin flipping example is a very nice way to
| put it. It works since the coins are interchangeable, you
| just count the number of heads or tails.
|
| If the coins were of different color and you took that
| into account, then it wouldn't work.
|
| It's not intuitive to me what gravity has to do with
| entropy though, as it's classically just a force and
| completely reversible (unlike entropy)? Ie if you saw a
| video of undisturbed objects only affected by gravity,
| you couldn't tell if the video was reversed.
| floxy wrote:
| > Ie if you saw a video of undisturbed objects only
| affected by gravity, you couldn't tell if the video was
| reversed.
|
| How does that work with things like black holes? If you
| saw an apple spiral out of a black hole, wouldn't you
| suspect that you were watching a reversed video? Even if
| you take account the gravitational waves?
| kgwgk wrote:
| If you saw a comet coming from the sun, or a meteorite
| coming from the moon, etc. you would also find that
| suspicious.
| immibis wrote:
| That's the question of why time only goes forwards. It
| seems to be that the universe started in an extremely
| low-entropy state. It will go towards high entropy. In a
| high entropy state (e.g. heat death, or a static black
| hole), there's no meaningful difference between going
| forwards or backwards in time - if you reverse all the
| velocities of the particles, they still just whizz around
| randomly (in the heat death case) or the black hole stays
| a black hole.
| meindnoch wrote:
| >Simple example: why ice melts in a warm room.
|
| Ice melting is simply the water molecules gaining enough
| kinetic energy (from collisions with the surrounding air
| molecules) that they break the bonds that held them in the
| ice crystal lattice. But at the microscopic level it's still
| just water molecules acting according to Newton's laws of
| motion (forgetting about quantum effects of course).
|
| Now, back on the topic of the article: consider a system of 2
| particles separated by some distance. Do they experience
| gravity? Of course they do. They start falling towards the
| midpoint between them. But where is entropy in this picture?
| How do you even define entropy for a system of 2 particles?
| ccozan wrote:
| Let me try to answer. Let's say the particles are
| experiencing gravity as a natural entropy phenomena. They
| will attract until they become so close that they are now
| seen as a single particle. The new system has a lower
| entropy and a higher gravity than before.
|
| Explanation seems very rudimentary but that is the gist of
| the theory.
|
| From my point of view, I might add the layer of information
| density. Every quantum fluctuation is an event and the more
| particles the more information is produced in a defined
| space volume. But there is no theory of information that is
| linked to the physics so ...that let me leave as that :).
| stephenitis wrote:
| Can you define quantum fluctuation?
| tsimionescu wrote:
| > But where is entropy in this picture? How do you even
| define entropy for a system of 2 particles?
|
| The answer is that this doesn't happen in a system with
| only 2 particles. The idea of gravity as an entropic
| phenomenon is that you introduce some other kind of
| particle that permeates spacetime, so there is no system
| that only contains 2 particles. You may use some idea like
| virtual particles from quantum field theory, or you may
| define "quanta of space time" as something that is not
| technically a particle but basically works like one in a
| handwavy sense.
|
| But the basic point of these entropy based theories is to
| explain gravity, and typcilaly spacetime itself, as an
| emergent result of a collection of numerous objects of some
| kind. This necessarily means that they don't make sense if
| applied to idealized systems with very few objects - which
| is why they typically posit such isolated systems simply
| can't actually exist in reality.
| aeonik wrote:
| My take, for what it's worth,
|
| Entropy isn't always the driver of physical change, sometimes
| it's just a map.
|
| Sometimes that map is _highly isomorphic_ to the physical
| process, like in gas diffusion or smoke dispersion. In those
| cases, entropy doesn 't just describe what happened, it
| _predicts_ it. The microstates and the probabilities align
| tightly with what's physically unfolding. Entropy is the
| engine.
|
| But other times, like when ice melts, entropy is a _summary_
| , not a cause. The real drivers are bond energies and phase
| thresholds. Entropy increases, yes, but only because the
| system overcame physical constraints that entropy alone can't
| explain. In this case, entropy is the receipt, not the
| mechanism.
|
| So the key idea is this: entropy's usefulness depends on how
| well it "sees" the real degrees of freedom that matter. When
| it aligns closely with the substrate, it feels like a law.
| When it doesn't, it's more like coarse bookkeeping after the
| fact.
|
| The second law of thermodynamics is most "real" when entropy
| _is_ the process. Otherwise, it's a statistical summary of
| deeper physical causes.
| lumost wrote:
| What makes entropy interesting is that you can describe
| _many_ physical processes through analysis of the systems
| degrees of freedom. This pattern repeats regularly despite
| the systems being radically different.
|
| So you can interpret entropy as being about as real as
| potential energy or newtons laws. Very useful for
| calculation, subject to evolution laws which are common
| across all systems - but potentially gives way as an
| approximation under a finer grained view (although the
| finer grained view is also subject to the same rules)
| geon wrote:
| It has been suggested that time too is derived from entropy.
| At least the single-directionality of it. That'd make entropy
| one of the most real phenomena in physics.
| kgwgk wrote:
| > Physical entropy governs real physical processes
|
| > the measure is not the same thing as the phenomenon it
| describes.
|
| There is some tension between those claims.
|
| The latter seems to support the parent comment's remark
| questioning whether a "fundamental physical interaction could
| follow from entropy".
|
| It seems more appropriate to say that entropy follows from
| the physical interaction - not to be confused with the
| measure used to describe it.
|
| One may say that pressure is an entropic force and physical
| entropy governs the real physical process of gas expanding
| within a piston.
|
| However, one may also say that it's the kinetic energy of the
| gas molecules what governs the physical process - which
| arguably is a more fundamental and satisfactory explanation.
| mjburgess wrote:
| Even if we take that view, gravity is still basically a similar
| case. What we call "gravity" is really an _apparent_ force,
| that isnt a force at all when seen from a full 4d pov.
|
| Imagine sitting outside the whole universe from t=0,t=end and
| observing one whole block. Then the trajectories of matter,
| unaffected by any force at all, are those we call
| gravitational.
|
| From this pov, it makes a lot more sense to connect gravity
| with some orderly or disorderly features of these trajectories.
|
| Inertia, on this view, is just a kind of hysteresis the matter
| distribution of the universe has -- ie., a kind of remembered
| deformation that persists as the universe evolves.
| tsimionescu wrote:
| > From this pov, it makes a lot more sense to connect gravity
| with some orderly or disorderly features of these
| trajectories.
|
| On the contrary, entropic gravity works pretty well for the
| Newtonian view of gravity as a force, and not the GR view of
| gravity as a deformation of space time and analogous to
| acceleration. Acceleration is a very elementary concept, one
| you find even in microscopic descriptions. Gravity being
| essentially the same thing makes it far more elementary than
| a concept like entropy, which only applies to large groups of
| particles.
|
| So, if the GR picture is the right one, if gravity and
| acceleration are essentially the same thing, its very hard to
| see how that aligns with gravity being an emergent phenomenon
| that only happens at large scales. However, if gravity is
| just a tendency for massive objects to come together, as in
| the Newtonian picture, that is perfectly easy to imagine as
| an entropic effect.
| prof-dr-ir wrote:
| Good question. You are absolutely right that entropy is always
| fundamentally a way to describe are our lack of perfect
| knowledge of the system [0].
|
| Nevertheless there is a distinct "reality" to entropic forces,
| in the sense that it is something that can actually be measured
| in the lab. If you are not convinced then you can look at:
|
| https://en.wikipedia.org/wiki/Entropic_force
|
| and in particular the example that is always used in a first
| class on this topic:
|
| https://en.wikipedia.org/wiki/Ideal_chain
|
| So when viewed in this way entropy is not _just_ a "made-up
| thing", but an effective way to describe observed phenomena.
| That makes it useful for effective but not fundamental laws of
| physics. And indeed the wiki page says that entropic forces are
| an "emergent phenomenon".
|
| Therefore, any reasonable person believing in entropic gravity
| will automatically call gravity an emergent phenomenon. They
| must conclude that there is a new, fundamental theory of
| gravity to be found, and this theory will "restore" the
| probabilistic interpretation of entropy.
|
| The reason entropic gravity is exciting and exotic is that many
| other searches for this fundamental theory start with a (more
| or less) direct quantization of gravity, much like one can
| quantize classical mechanics to arrive at quantum mechanics.
| Entropic gravity posits that this is the wrong approach, in the
| same way that one does not try to directly quantize the ideal
| gas law.
|
| [0] Let me stress this: there is no entropy without probability
| distributions, even in physics. Anyone claiming otherwise is
| stuck in the nineteenth century, perhaps because they learned
| only thermodynamics but not statistical mechanics.
| meindnoch wrote:
| Sure, I'm not denying that entropy exists as a concept, that
| can be used to explain things macroscopically. But like you
| said, it's origins are statistical. To me, temperature is
| also a similar "made up" concept. We can only talk about
| temperature, because a sufficiently large group of particles
| will converge to a single-parameter distribution with their
| velocities. A single particle in isolation doesn't have a
| temperature.
|
| So if they say gravity might be an entropic effect, does that
| mean that they assume there's something more fundamental
| "underneath" spacetime that - in the statistical limit -
| produces the emergent phenomenon of gravity? So it isn't the
| entropy of _matter_ that they talk about, but the entropy of
| something else, like the grains of spacetime of whatever.
| spacecadet wrote:
| Im an idiot, let's get that out of the way first. I think
| that your temperature analogy answered your own question.
|
| I guess my question in turn is, if we imagine a universe at
| the end of time(?), one that maybe dominated by a few black
| holes and not much else. Would an observer experience
| gravity if place sufficiently far enough way? Or even
| further, if nothing is left in the universe at all.
| Assuming that doesn't cause a big crunch, rip, or
| whatever...
| flufluflufluffy wrote:
| Yes, exactly. The model is based on (in the first approach)
| a "lattice" of some type of undiscovered particle-like
| thing (what they refer to as "qubits" in the article, which
| is unfortunate because it is NOT the same "qubit" from
| quantum computing) permeating space time. Or maybe more
| aptly, it is that lattice from which spacetime emerges. And
| what we observe as the force of gravity emerges from the
| entropic forces happening in this lattice.
| simiones wrote:
| > You are absolutely right that entropy is always
| fundamentally a way to describe are our lack of perfect
| knowledge of the system [0].
|
| > [0] Let me stress this: there is no entropy without
| probability distributions, even in physics.
|
| The second item doesn't entail the first. Probabilities can
| be seen as a measure of lack of knowledge about a system, but
| it isn't necessarily so. A phenomenon can also be
| inherently/fundamentally probabilistic. For example, wave
| function collapse is, to the best of our knowledge, an
| inherently non-deterministic process. This is very relevant
| to questions about the nature of entropy - especially since
| we have yet to determine if it's even possible for a large
| system to be in a non-collapsed state.
|
| If it turns out that there is some fundamental process that
| causes wave function collapse even in perfectly isolated
| quantum systems, then it would be quite likely that entropy
| is related to such a process, and that it may be more than a
| measure of our lack of knowledge about the internal state of
| a system, and instead a measurement of the objective
| "definiteness" of that state.
|
| I am aware that objective collapse theories are both
| unpopular and have some significant hurdles to overcome - but
| I also think that from a practical perspective, the gap
| between the largest systems we have been able to observe in
| pure states versus the smallest systems we could consider
| measurement devices is still gigantic and leaves us quite a
| lot of room for speculation.
| mjanx123 wrote:
| Entropy is the opposite of potential
| echelon wrote:
| Entropy is complicated beyond just a Rankine or Carnot cycle.
|
| Biology thrives at the ebbs, flows, and eddies of entropy.
| Predation. Biochemical flux. There are arrows flowing every
| which way, and systems that keep it finely tuned.
|
| This theory, based on my surface level reading and
| understanding, is that the aggregate particle-level entropy
| within sub light speed systems creates gravity.
| whereismyacc wrote:
| It sounds like you're talking about information entropy which
| to my understanding is analogue to but not the same as entropy
| in physics?
| ajkjk wrote:
| It pretty much is the same, except that entropy in physics
| usually has a constant in front of it.
| IsTom wrote:
| If you want to only have one possible past (i.e. can't destroy
| information) then when you end up in one branch of quantum
| state you need to "store" enough information to separate you
| form other branches and you really do need to have multiple
| possible microstates to differentiate them. If you look post-
| factum obviously you did end up in a specific state, but
| statistics do their work otherwise.
| bmitc wrote:
| > It's a made-up thing by humans.
|
| All of physics is made up by humans.
| sixo wrote:
| This comment thread is exhibit N-thousand that "nobody really
| understands entropy". My basic understanding goes like this:
|
| In thermodynamics, you describe a system with a massive number
| of microstates/dynamical variable according to 2-3 measurable
| macrostate variables. (E.g. `N, V, E` for an ideal gas.)
|
| If you work out the dynamics of those macrostate variables, you
| will find that (to first order, i.e. in the thermodynamic
| limit) they depend _only_ on the form of the entropy function
| of the system `S(E, N, V)`, e.g. Maxwell relations.
|
| If you measured a few more macrostate variables, e.g. the
| variance in energy `sigma^2(E)` and the center of mass `m`, or
| anything else, you would be able to write new dynamical
| relations that depend on a new "entropy" `S(E, N, V,
| sigma^2(E), m)`. You could add 1000 more variables, or a
| million--e.g every pixel of an image--basically up until the
| point where the thermodynamic limit assumptions cease to hold.
|
| The `S` function you'd get will capture the contribution of
| every-variable-you're-marginalizing-over to the relationships
| between the remaining variables. This is the sense in which it
| represents "imperfect knowledge". Entropy dependence arises
| _mathematically_ in the relationships between macrostate
| variables--they can only couple to each by way of this function
| which summarizes all the variables you don 't know/aren't
| measuring/aren't specifying.
|
| That this works is rather surprising! It depends on some
| assumptions which I cannot remember (on convexity and
| factorizeabiltiy and things like that), but which apply to most
| or maybe all equilibrium thermodynamic-scale systems.
|
| For the ideal gas, say, the classical-mechanics, classical-
| probability, and quantum-mechanic descriptions of the system
| all reduce to the same `S(N, V, E)` function under this
| enormous marginalization--the most "zoomed-out" view of their
| underlying manifold structures turns out to be identical, which
| is why they all describe the same thing. (It is surprising that
| seemingly obvious things like the size of the particles would
| _not_ matter. It turns out that the asymptotic dynamics depend
| only on the information theory of the available "slots" that
| energy can go into.)
|
| All of this appears as an artifact of the limiting procedure in
| the thermodynamic limit, but it may be the case that it's more
| "real" than this--some hard-to-characterize quantum decoherence
| may lead to this being not only true in an extraordinarily
| sharp first-order limit, but actually physically _true_. I
| haven 't kept up with the field.
|
| No idea how to apply this to gravity though.
| immibis wrote:
| Entropy can be defined as the logarithm of the number of
| microstates in a macrostate. Since transition between
| microstates is reversible, and therefore one-to-one (can't
| converge on any particular microstate, can't go in cycles, have
| to be something like a random walk) we're more likely to end up
| in a macrostate that holds a larger number of microstates.
|
| For example, there are many more ways your headphone cord can
| be tangled than untangled, so when you pull it out of your
| pocket, and it's in a random state, then it's very likely to be
| tangled.
|
| If entropy causes gravity, that means there are more somehow
| more microstates with all the mass in the universe smooshed
| together than microstates with all the mass in the universe
| spread apart.
| Ma8ee wrote:
| Entropy is certainly a physical "thing", in the sense that it
| affects the development of the system. You can equally well
| apply your argument that it isn't a physical thing because it
| doesn't exist on a microscopic scale to temperature.
| Temperature doesn't exist when you zoom in on single particles
| either.
|
| There's no reason to involve our knowledge of the system.
| Entropy is a measure of the number of possible micro states for
| a given system, and that number exists independently of us.
| kgwgk wrote:
| > Entropy is a measure of the number of possible micro states
| for a given system, and that number exists independently of
| us.
|
| That number also exists independently of the system! I can
| imagine any system and calculate the corresponding number.
|
| (And for an even more philosophical question, does the
| "system" really exist independently of us? What separates the
| "system" from anything else? Is every subset of the universe
| a "system"?)
| tsoukase wrote:
| For years I thought the same for entropy. But now I believe it
| is fundamentaly impossible to know each micro state,
| irrespective our tools and methods. And this happens like and
| due to Heisenberg's uncertainty principle.
|
| So all events are irreversible and entropy is always
| increasing. Perfection is only theoretical.
| metalman wrote:
| gravity=time
| evanb wrote:
| whoa dude, that means gravity = money by transitivity. deep.
| the_sleaze_ wrote:
| And 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 wrote:
| So can we make hoverboards by losing money?
| pif wrote:
| As 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 wrote:
| The 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 wrote:
| Please, how is the article related to MOND's theories?
| lewdwig wrote:
| In 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 wrote:
| From 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 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 :
|
| > _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?_
| andrewflnr wrote:
| They both have to do with very weak gravitational fields.
| cryptonector wrote:
| u/lewdwig's point was that if an emergent gravity theory
| made the sorts of predictions that MOND is meant to, _then_
| that would be a prediction that could be tested. The MOND
| thing is just _an example_ of predictions that an emergent
| theory might make.
| dawnofdusk wrote:
| Deriving existing theories of gravity is an important test of
| the theory, it's not a problem at all. It's only a problem if
| you can only do this with more free parameters than the
| existing theory and/or the generalized theory doesn't make
| any independent predictions. Seems like in the article the
| former may be true but not the latter.
| cryptonector wrote:
| If such a theory makes no new predictions but is simple /
| simpler than the alternative, then it is a better theory.
| cantor_S_drug wrote:
| Sometimes I wonder, imagine if our physics never allowed for
| Blackholes to exist. How would we know to stress test our
| theories? Blackholes are like standard candles in cosmology
| which allows us to make theoretical progress.
| mycatisblack wrote:
| And each new type of candle becomes a source of fine-tuning
| or revision, progressing us with new ways to find the next
| candles - cosmological or microscopic.
|
| Which kinda points to the fact that we're not smart enough to
| make these steps without "hints". It's quite possible that
| our way of working will lead to a theory of everything in the
| asymptote, when everything is observed.
| the__alchemist wrote:
| This is why I'm skeptical of theories like Wolfram's: It feels
| like an overfit based on this: It produces all sorts of known
| theories (special relativity, parts of QM, gravity etc), but
| doesn't make new testable predictions, or new fundamentals.
| When I see 10 predictions emerge from the theory, and they all
| happen to be ones we already known of... Overfit.
| emtel wrote:
| Jonathan Gorard goes through a handful of testable
| predictions for the hypergraph stuff here:
| https://www.youtube.com/watch?v=XLtxXkugd5w
| ojo-rojo wrote:
| But that means we'd prefer whichever theory our species had
| landed on first. Basing our preference for a theory on that
| timing seems kind of arbitrary to me. If they're the same in
| other respects, I'd take a look at both sides to see if there
| are other compelling reasons to focus on one or the other,
| such as which is simpler. Of course if they make different
| predictions that'd be even better, time to get to testing :)
| generalizations wrote:
| A positive example would be the periodic table - the
| pattern to the elements made sense, but also exposed
| 'holes' in the table which were later filled in as we
| discovered additional elements. Wolfram may be closer to
| inventing epicycles to explain orbits - which is interesing
| and technically challenging and probably tickles his mind,
| but doesn't actually generate new knowledge.
| elyase wrote:
| Between two models the one with the shorter Minimum Description
| Length (MDL) will more likely generalize better
| nitwit005 wrote:
| But, think of all the fun math we get to do before someone
| shows it's an unworkable idea.
| brador wrote:
| Anti 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 wrote:
| Vacuums don't suck; high pressure repels.
|
| Similarly, umbrellas aren't places to stand under when it's not
| raining.
| cwharris wrote:
| This 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.
| konschubert wrote:
| This is not a philosophical discussion
| cwharris wrote:
| This 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 wrote:
| Entropy 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 wrote:
| We'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?
| cwharris wrote:
| You're right. the cadence is written by ChatGPT. I'm pretty
| terrible at keeping my thoughts cohesive, so I often use it
| as a post processor. I'll try not to do that.
|
| Because you had the decency to respond, I'll spent some more
| time thinking about this and see if I can come up with a more
| well rounded response that incorporates more of the
| traditional language of physics. But to your point about
| entropy not being a "force", you're probably right. Someone
| got to choose what that word means, and I'm probably not
| using their definition. But let me ask you this... would you
| rather have a book that explains everything and not know how
| to read it, or trust your own eyes ears and hands, and not be
| able to share it?
| prophesi wrote:
| > would you rather have a book that explains everything and
| not know how to read it, or trust your own eyes ears and
| hands, and not be able to share it?
|
| Maybe use AI to help you understand TFA instead of writing
| gut reactions to the title.
| cwharris wrote:
| I... Do... With quite a lot of articles... And I build
| semiconductors in my garage using what I learn.
|
| I just don't see how this particular article would be
| beneficial, even if it _were_ correct.
| prophesi wrote:
| Are these the very same semiconductors writing your
| comments? NGL, a 9 year old account with 0 posts that
| suddenly starts posting AI-assisted comments is very
| suspicious.
| cwharris wrote:
| The problems I wanted to solve couldn't be solved with
| software, so I started researching ceramic
| semiconductors, starting with positive temperature
| coefficient ceramics as fail-safe heating elements. The
| geometry I needed to manufacture for that project wasn't
| scalable in a way that solved the problem for enough
| people, so I switched to working on DC cold atmospheric
| plasma. Saw enough progress there to convince myself it's
| possible, but wasn't happy with the current HV supplies
| on the market, so I'm working on making my own based on
| converting compressed argon in to a high voltage source
| that self-regulates based on plasma generation in an
| attempt to not exceed metastable argon charge levels,
| which would produce NOx and Ozone at completely harmless
| levels (unless maybe you're using it during surgery) but
| are heavily regulated.
|
| It's uhh... been a ride.
|
| But yes, posting to hacker news is a new thing. Because
| I'm seeing the limitations of the world we live in
| through the lens of someone who's gone through industry
| long enough to know how slowly controlled progress is,
| and beginning to see what happens when you apply
| semiconductors to more than just microprocessors on your
| own terms. The world is stagnating, not because we don't
| have what it takes to bring about the future... but
| because 1) we do, 2) the people in control don't care to
| make it happen, and 3) everyone has their hands tied up
| in corperate profits while we wait for someone to make a
| move that makes things better.
|
| I'm just... done waiting.
| echelon wrote:
| Because it has emdashes and ellipses that Chrome, Firefox,
| Mac, Linux, and Android text input controls do not natively
| produce.
|
| I don't know about iPhone.
|
| If you see these artifacts, it was authored in some other
| software (be it an editor or LLM) and pasted over.
| cryptonector wrote:
| iPhone definitely turns `--` into `--`, at least sometimes.
| trealira wrote:
| Android does let you produce em dashes. I'm typing this
| with Google Keyboard right now.
|
| If you hold the hyphen button, you get options for an
| underscore, an em dash (--) an en dash (-), and the dot
| symbol (*). The ellipsis (...) can be written by holding
| the period button.
|
| But yeah, the commenter admitted it was authored by AI. But
| even if you converted all the em dashes to "--", it would
| still have a ChatGPT cadence.
|
| > There's a missing piece here -- maybe coherence,
| resonance, or field attraction. But "just entropy"? That
| doesn't explain formation. It explains dissolution.
|
| Even ignoring the em dash, it just screams ChatGPT.
| cwharris wrote:
| I like how people are recognizing "OH THIS IS TOKEN
| OUTPUT", and that's like... the only thing you can come up
| with to refute the argument?
|
| Like not the actual content or meaning of the text, which I
| chose to post, but the mere fact that it wasn't typed in to
| a keyboard directly in a hacker news text box, but rather
| pasted after using a tool to refine the verbiage.
|
| Honestly? Great test for most posts. We live in a world
| surrounded by people who are just copy and pasting ChatGPT
| answers like a magic 8 ball, and I respect your instinct to
| try to avoid those.
|
| But that's not how I use ChatGPT, because I understand how
| language models work and choose to use them intentionally
| to help me nagivate ideas and learn new concepts (as well
| as write memos after-the-fact). Not just take a hollow
| "sounds good" response and post it to take up people time.
|
| :shrug:
| cwharris wrote:
| Here's the non-ChatGPT rant that I was attempting to not spew
| all over the internet.
|
| > "There's some kind of gas or some thermal system out there
| that we can't see directly," >
|
| Posit that there's something we don't know about, and we're
| supposing it's gas-like. This is what I like to refer to as
| "imagination", and it's a great way to start thinking about
| problems. The fact that it's showing up in an article
| suggests they didn't get much further than imagination, but
| I'll keep reading...
|
| > "But it's randomly interacting with masses in some way,
| such that on average you see all the normal gravity things
| that you know about: The Earth orbits the sun, and so forth."
| >
|
| Cool. We're back on everything being "random" again. Modern
| interpretations of quantum mechanics has really torn a hole
| in the idea of causality by replacing it with the idea that
| we can't explain why things happen, but we CAN model it
| statistically, so we'll assume the model is right and stop
| looking for causal relationships entirely." It's lazy
| pessimistic psuedo-science, and I don't buy it. I don't
| outright REFUTE it, but I'm not basing my understanding of
| nature on it just because a bunch of smart people decided to
| stop looking.
|
| On the paper the article refers to:
|
| > Consider a pair of massive pistons with a non-interacting
| gas between them, as in Fig. 1. >
|
| Cool. Happy to consider it. But I am curious... Are there
| existing examples of particles that do not interact with
| particles of like kind? Neutrinos and Photons come to mind.
| But has anyone proven that they don't interact, or are we
| just assuming they don't interact because we haven't put the
| effort in to try and detect interactions? But sure, let's
| consider the possibility.
|
| > What this exercise demonstrates is that the two pistons
| feel an effective force between them, namely the pressure,
| which is mediated by the gas rather than some fundamental
| quantized field. >
|
| Honestly? I love this. I don't care about "fields" at all,
| personally. I feel like it's more intuitive to think of
| fields as reinforcement of particle interactions over time
| and space. An electon moves? So do all of the others. A lot
| of them move the same way? The others feel that combined
| movement at distance according to C. Magnetic flux? Interplay
| of electron inertia reinforcment delayed by the time it takes
| for the repulsive forces to make their way around a coil (or
| whatever other medium according to it's influence) and allow
| spin to align. Falsifiable? Yes. Relevant intuitive
| observation? Yes. Taken the time to write out the math myself
| in languages I don't know? No.
|
| > <... lot's of math that proves individual hypothetical
| (sorry, theoretical) particle interactions can explain how
| gravity emerges...> >
|
| Cool. I'm almost certain that if I took the time to check
| their math, it would be _meaningfully accurate_ and
| absolutely show that this _is_ a way you can view gravity.
|
| But let me ask you... Why the hell would anyone want to think
| about gravity like that, and why are we trying to explain
| things in terms of entropy when it clearly has no
| applications outside of "well, I guess everything is left up
| to chance, and there's nothing left to be discovered." I
| reject this hypothesis. I reject the idea that everything we
| see, feel, hear, and know was at one point non-existant, and
| somehow emerged at this level of complexity such that we are
| capable of not only cognition but also direct observation of
| physical phenomena while simultaneously _being_ physical
| phenomena ourselves. There is something else. And no, it's
| not "God". But it sure as hell isn't "everything's just
| falling apart in interesting ways". And I _get_ that that's
| not the "full idea" behind entropy, but it _is_ entropy's
| brand identity, and it _is_ the implication behind entropy as
| the driving force of nature (sorry, I used force again. I
| forget we 're not allowed to say that about the thing we're
| using to explain how all of the real forces emerge. my bad).
| Heat death of the universe as a result of entropy? I'm
| onboard. Red shift? I get it. Entropy is a great "welp I
| guess that's the reason again", but the mental gymnastics it
| takes to represent gravity as a result of this? Give me a
| freaking break.
|
| There's a simpler explanation for all of this that models
| well across domains, and nobody is willing to admit it
| because it doesn't fit the narrative. Phase-lock. Waveforms
| that mesh together in torsional space time reinforce each
| other, sometimes purely locally through identity changes
| (fusion), and sometimes via interdependant standing waves
| (non-fundamental particles, atoms, molecules, etc etc).
| Entropy is just what happens when coherence fails to resolve
| locally and must resolve non-locally (chemical interactions,
| fission, dielectric breakdown, photoelectric effect). Most
| things can be modelled this way: as stable geometric
| configurations of quantum wave functions representing self-
| reinforcing torsional spacetime harmonics. And if you take a
| second to consider it, maybe this single paragraph _is_ a
| more intuitive explanation of gravity, too.
| ajkjk wrote:
| There is a whole article explaining it... if you don't read the
| article, how do you expect to know the idea?
| cantor_S_drug wrote:
| Actually Roger Penrose also had this line of thinking if my
| memory serves right.
| cryptonector wrote:
| You have it backwards. The lowest entropy state of the universe
| would be if there were no attractive forces, only repellent
| forces, as then all particles would be forced into something of
| an expanding lattice, but with all particles equidistant from
| all nearest neighbors (of the same type).
|
| It is gravity which disrupts this and causes clumping, and
| _that_ _increases_ entropy.
|
| I know it's confusing because normally one would think of a
| cloud of gas as more disordered than the star it might collapse
| into, but that is not so. For one the star would be much
| hotter, and the motions of every particle in the star much more
| chaotic.
| neuroelectron wrote:
| The 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 wrote:
| Doesn't sound intuitive at all really...
| neuroelectron wrote:
| You 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 wrote:
| > 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 wrote:
| This 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.
| Xcelerate wrote:
| Warm objects actually do weigh more than their counterfactual
| cold versions haha. The stress energy tensor is the quantity
| to look at here.
| neuroelectron wrote:
| I didn't know this, thanks for sharing.
|
| https://herebeanswers.com/things-weigh-heavier-or-lighter-
| wh...
| patcon wrote:
| I feel like you have somehow found the least
| authoritative source for the wonderful new information
| provided...
|
| why did you choose that one? serious question, because
| I'm trying to understand your process (and yes, maybe
| gently challenging it, but unsure if I should, bc you are
| clearly knowledgeable in specific ways about this)
| neuroelectron wrote:
| Thanks, I appreciate it
| UncleSlacky wrote:
| Relevant paper: https://iopscience.iop.org/article/10.1088/
| 0143-0807/8/2/006...
|
| Abstract: "According to the weak form of the equivalence
| principle all objects fall at the same rate in a
| gravitational field. However, recent calculations in
| finite-temperature quantum field theory have revealed that
| at T>0 heavier and/or colder objects actually fall faster
| than their lighter and/or warmer counterparts. This
| unexpected result is demonstrated using elementary quantum
| mechanical arguments."
|
| Downloadable here:
| https://www.academia.edu/download/109363694/download.pdf
| danparsonson wrote:
| > Seems pretty intuitive to me
|
| OK, but it's nonsense. Apart from whatever-you're-talking-
| about-with-C, quantum fluctuations are not Brownian motion;
| Brownian motion is the visible effect of a lot of invisible
| particles interacting kinetically with macroscopic particles
| like dust, making those macroscopic particles appear to vibrate
| of their own accord. Atoms that cannot be seen in a microscope
| flying around in straight lines and randomly bumping into dust
| particles that can be seen.
|
| https://en.m.wikipedia.org/wiki/Brownian_motion
| Caelus9 wrote:
| It'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 wrote:
| Couldn'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 wrote:
| Descartes had a similar idea, but as far as I remember, it
| requires ether.
| ang_cire wrote:
| No, many asteroids have detectable, "functional" (e.g. they
| pull dust towards them) gravitational fields, but are not
| spinning like planets.
| vkou wrote:
| Given 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 wrote:
| Entropic 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
|
| [1] https://www.youtube.com/watch?v=Incnv2CfGGM
| sim7c00 wrote:
| but 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 wrote:
| You need to reread the middle only. It's a kind of "vacuum"
| effect.
| franktankbank wrote:
| No you are right. You can't invoke gravity in an analogy
| trying to explain gravity.
| cwmoore wrote:
| Not without a bridge for the metaphor to generalize. What
| parameters map to the nutjar's selective force, size, and
| mass?
| dudeinjapan wrote:
| The same effect could be replicated in a zero-gravity
| environment using an alternative background force
| (centrifugal force, vacuum suction, electromagnetism, etc.)
| nitwit005 wrote:
| This problem of explaining gravity with gravity is a bit
| pervasive, and it frustrated the heck out of me as a kid.
| hcarvalhoalves wrote:
| In other words, gravity would be explainable by statistical
| mechanics (like heat)?
| abetusk wrote:
| That's the allure, that gravity is a derived effect from
| statistical mechanics. Thus the name 'entropic attraction'.
| ndriscoll wrote:
| Aren't more massive particles smaller though (in terms of de
| Broglie wavelength, at least), so they'd have a smaller
| "shadow"? Or do different forces have different cross-sections
| with different relationships to mass, so a particle's "size" is
| different for different interactions (and could be proportional
| to mass for gravity)?
|
| Actually this is currently blowing my mind: does the (usual
| intro QM) wavefunction only describe the probability amplitude
| for the position of a particle _when using photon interaction
| to measure_ , and actually a particle's "position" would be
| different if we used e.g. interaction with a Z boson to define
| "position measurement"?
| bobbylarrybobby wrote:
| The momentum wavefunction (or more properly, the wavefunction
| in the momentum basis) completely determines the position
| wavefunction (wavefunction in the position basis). And we can
| probe the momentum wavefunction with any particle at all, by
| setting up identical (say) electrons and seeing the momentum
| they impart on a variety of test particles. That is to say,
| the probability distribution of momentum of a particle does
| not depend on what we use to probe it.
|
| As the position wavefunction is now completely determined in
| a probe-agnostic matter, it would be hard to justify calling
| a probe that didn't yield the corresponding probability
| distribution a "position measurement".
| Someone wrote:
| > 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)
|
| That doesn't make sense to me. If larger objects move slower,
| don't they move faster relative to the (accelerating) reference
| frame of the container?
|
| Also, conventional wisdom has it that shaking (temporarily)
| creates empty spaces, and smaller objects 'need' smaller such
| spaces to fall down, and thus are more likely to fall down into
| such a space.
| abetusk wrote:
| > That doesn't make sense to me. If larger objects move
| slower, don't they move faster relative to the (accelerating)
| reference frame of the container?
|
| Yes? But so what? The relevant interaction is between the
| peanuts and the Brazil it's.
|
| > Also, conventional wisdom has it that shaking (temporarily)
| creates empty spaces, and smaller objects 'need' smaller such
| spaces to fall down, and thus are more likely to fall down
| into such a space.
|
| Right, but preferentially under the larger Brazil nuts.
| hellohello2 wrote:
| Not a physicist either but this passage from the Feynman
| lectures seem related to what you are describing:
| https://www.feynmanlectures.caltech.edu/I_07.html
|
| "Many mechanisms for gravitation have been suggested. It is
| interesting to consider one of these, which many people have
| thought of from time to time. At first, one is quite excited
| and happy when he "discovers" it, but he soon finds that it is
| not correct. It was first discovered about 1750. Suppose there
| were many particles moving in space at a very high speed in all
| directions and being only slightly absorbed in going through
| matter. When they are absorbed, they give an impulse to the
| earth. However, since there are as many going one way as
| another, the impulses all balance. But when the sun is nearby,
| the particles coming toward the earth through the sun are
| partially absorbed, so fewer of them are coming from the sun
| than are coming from the other side. Therefore, the earth feels
| a net impulse toward the sun and it does not take one long to
| see that it is inversely as the square of the distance--because
| of the variation of the solid angle that the sun subtends as we
| vary the distance. What is wrong with that machinery? It
| involves some new consequences which are not true. This
| particular idea has the following trouble: the earth, in moving
| around the sun, would impinge on more particles which are
| coming from its forward side than from its hind side (when you
| run in the rain, the rain in your face is stronger than that on
| the back of your head!). Therefore there would be more impulse
| given the earth from the front, and the earth would feel a
| resistance to motion and would be slowing up in its orbit. One
| can calculate how long it would take for the earth to stop as a
| result of this resistance, and it would not take long enough
| for the earth to still be in its orbit, so this mechanism does
| not work. No machinery has ever been invented that "explains"
| gravity without also predicting some other phenomenon that does
| not exist."
| AnotherGoodName wrote:
| It also doesn't account for time dilation in a gravity well
| however i still think the general idea has some merit if you
| think of it as being bombarded by massless 'action
| potentials' on all sides with mass absorbing that field to
| some to enable translation in space time.
|
| I get this is vague spitballing but essentially an 'action
| potential' would allow mass to move. Higher temperature mass
| interacts more, lower temperature interacts less. Mass with
| momentum would be biased to absorb more from one side so it
| travels in a specific direction in space more than others
| (the idea i'm getting at is that all movement in space only
| occurs with interaction with this field), this also would
| counteract issues with moving mass interacting more on a
| specific side - the very bias of mass with momentum to absorb
| more on one side means that from that masses point of view it
| has the same action potentials interacting from all sides.
| Mass shielded behind mass receives fewer action potentials so
| experiences exactly the effect that you can call time
| dilation. Mass shielding other mass from action potentials
| also means that mass accelerates towards other mass.
|
| Essentially its the above but instead of a massive particle
| hitting other mass from all sides it's a field that allows
| mass to experience a unit of time.
| FilosofumRex wrote:
| This is a better YouTube video describing granular physics and
| shows the speed (amplitude) of vibrations can cause
| counterintuitive arrangements of particles.
|
| At lower speeds you get something akin to Newtonian gravity but
| at higher velocities you get something resembling MOND gravity
| where galaxies clusters and large voids appear - no dark matter
| needed.
|
| https://www.youtube.com/watch?v=HKvc5yDhy_4
| abetusk wrote:
| Thanks for the link, very interesting. I'll have to check out
| the paper but just watching the video it seems all these
| counter intuitive effects can be described from the
| oscillations being related to the size of the chamber.
|
| For example if I were to roll the chamber at a very low
| frequency, I would expect the particles to clump on one side,
| then the other and so on. This is not really so surprising
| and the frequency will depend on the chamber dimensions.
| hatsunearu wrote:
| My interpretation of entropy is that if you have X states that
| are equally probable, but not all states are distinct from each
| other in some sense, then the next state will likely be one
| where the states satisfying that condition is most numerous.
|
| For example, if you flip N coins, there are 2^N states
| available once the flip is done. Each outcome has an 1/2^N
| probability of outcome. There's only one state where all of the
| states show all heads. While there's only one state where coins
| numbers 1-N/2 are heads, and N/2-N are tails, so that
| particular outcome is 1/2^N, if all we care is the macroscopic
| behavior of "how many heads did we get"--we'll see that we got
| "roughly" N/2 heads especially as N gets larger.
|
| Entropy is simply saying there's a tendency towards these
| macroscopically likely groups of states.
| collaborative wrote:
| You had lost me until you mentioned the kitty litter. I am now
| enlightened, thanks
| fourthark wrote:
| > "The ontology of all of this is nebulous"
| amai wrote:
| So entropy can curve spacetime? My fridge locally lowers entropy,
| does that mean inside my fridge gravity is lower than outside?
| raindeer2 wrote:
| Wonder 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 wrote:
| See also: emergent fox-treasure gravity in Skyrim:
| 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.
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