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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

#181

Post by AlexandrB »

meindnoch wrote: post #17
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.

>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).

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

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

#182

Post by vkou »

deadbabe wrote: post #153

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?

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.

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

#183

Post by colanderman »

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.

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

#184

Post by cwharris »

prophesi wrote: post #171
cwharris wrote: post #163

Earlier quoted context omitted.

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.

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.

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.

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

#185

Post by antonvs »

ajkjk wrote: post #113
mr_mitm wrote: post #64

Earlier quoted context omitted.

Just look at the definition of entropy. Knowledge about a system never enters the equation. S := -k_B sum p_i ln (p_i)

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. T…

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.

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

#186

Post by hellohello2 »

abetusk wrote: post #160

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 wh…

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."

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

#187

Post by the_sleaze_ »

evanb wrote: post #144
metalman wrote: post #18

gravity=time

whoa dude, that means gravity = money by transitivity. deep.

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.

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

#188

Post by layer8 »

MathMonkeyMan wrote: post #6

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, "…

From the article, they don’t claim Einstein‘s field equations yet, just classical Newtonian gravity, at present.

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

#189

Post by cwmoore »

franktankbank wrote: post #176
sim7c00 wrote: post #164

Earlier quoted context omitted.

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

No you are right. You can't invoke gravity in an analogy trying to explain gravity.

Not without a bridge for the metaphor to generalize. What parameters map to the nutjar’s selective force, size, and mass?

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

#190

Post by [deleted] »

echelon wrote: post #129
heyjamesknight wrote: post #106

Earlier quoted context omitted.

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.

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.

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