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Is gravity just entropy rising? Long-shot idea gets another look

quantamagazine.org

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Re: Is gravity just entropy rising? Long-shot idea gets another look

#21

Post by MaxikCZ »

bravesoul2 wrote: post #9
john_moscow wrote: post #2

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.

> 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?

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?

Re: Is gravity just entropy rising? Long-shot idea gets another look

#22

Post by logicchains »

meindnoch wrote: post #15

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 fu…

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.

Re: Is gravity just entropy rising? Long-shot idea gets another look

#23

Post by willvarfar »

meindnoch wrote: post #15

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 fu…

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

Re: Is gravity just entropy rising? Long-shot idea gets another look

#24

Post by antonvs »

meindnoch wrote: post #15

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 fu…

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.

Re: Is gravity just entropy rising? Long-shot idea gets another look

#26

Post by mjburgess »

meindnoch wrote: post #15

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 fu…

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.

Re: Is gravity just entropy rising? Long-shot idea gets another look

#28

Post by refactor_master »

antonvs wrote: post #24
meindnoch wrote: post #15

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 fu…

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. Bol…

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.

Re: Is gravity just entropy rising? Long-shot idea gets another look

#29

Post by HelloNurse »

antonvs wrote: post #24
meindnoch wrote: post #15

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 fu…

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. Bol…

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.

Re: Is gravity just entropy rising? Long-shot idea gets another look

#30

Post by holowoodman »

bandrami wrote: post #27
holowoodman wrote: post #25

Earlier quoted context omitted.

Virtual Particles!

Was that de Broglie's thing? I always thought it didn't get a fair shake

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...

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