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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

#111

Post by danparsonson »

neuroelectron wrote: post #105

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 questio…

> 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

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

#112

Post by ajkjk »

whereismyacc wrote: post #54
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…

It sounds like you're talking about information entropy which to my understanding is analogue to but not the same as entropy in physics?

It pretty much is the same, except that entropy in physics usually has a constant in front of it.

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

#113

Post by ajkjk »

mr_mitm wrote: post #64
kgwgk wrote: post #52

Earlier quoted context omitted.

> 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.

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.

The same model works for physical entropy without much modification; the imperfect knowledge is the difference between knowing a macrostate versus the exact microstate.

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

#114

Post by mr_toad »

jstanley wrote: post #34
killerstorm wrote: post #32

Earlier quoted context omitted.

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

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...

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.

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

#115

Post by tsimionescu »

kgwgk wrote: post #100
tsimionescu wrote: post #83

Earlier quoted context omitted.

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,…

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…

> 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.

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

#116

Post by neuroelectron »

ajkjk wrote: post #108
neuroelectron wrote: post #105

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 questio…

Doesn't sound intuitive at all really...

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.

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

#117

Post by parineum »

steamrolled wrote: post #109
neuroelectron wrote: post #105

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 questio…

> 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?

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.

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

#118

Post by [deleted] »

parineum wrote: post #117
steamrolled wrote: post #109

Earlier quoted context omitted.

> 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?

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.

[deleted]

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

#119

Post by Xcelerate »

steamrolled wrote: post #109
neuroelectron wrote: post #105

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 questio…

> 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?

Warm objects actually do weigh more than their counterfactual cold versions haha. The stress energy tensor is the quantity to look at here.

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

#120

Post by jblezo »

bravesoul2 wrote: post #98
MaxikCZ wrote: post #21

Earlier quoted context omitted.

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/particle…

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?

Spacetime curvature.

Like if you dropped the earth on a giant sheet, it would stretch the sheet more than what the moon would have.

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