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

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

#231

Post by buggyipadmettoo »

aeonik wrote: post #60
antonvs wrote: post #24

Earlier quoted context omitted.

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…

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,…

Just swap out "my take, for what it's worth" For "according to ChatGPT"

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

#232

Post by quantadev »

pif wrote: post #40

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.

An observable is always the strongest evidence but there's also the improbability of a mathematical coincidence that can serve as almost as strong evidence. For example the fact that the Bekenstein-Hawking entropy of an Event Horizon comes out to exactly be the surface area divided by plank-length-square units, seems to me almost a proof that nothing really falls into EHs. They only make it to the surface. I'm not saying Holographic Theory is correct, but it's on the right track.

My favorite conjecture is that what happens is things effectively lose a dimension when they reach the EH surface, and become like a "flatlander" (2D) universe, having only two degrees of freedom on the surface. For such a 2D universe their special "orthogonal" dimension they'd experience as "time" is the surface normal vector. Possibly time only moves forward for them when something new "falls in" causing the sphere to expand.

This view of things also implies the Big Bang is wrong, if our universe is a 3D EH. Because if you roll back the clock on an EH back to when it "formed" you don't end up at some distant past singularity; you simply get back to a time where stuff began to clump together from higher dimensions. The universe isn't exploding from a point, it's merely expanding because it itself is a 3D version of what we know as Event Horizons.

Just like a fish can't tell it's in water, we can't tell we're on a 3D EH. But we can see 2D versions of them embedded in our space.

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

#233

Post by quantadev »

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…

Bekenstein-Hawking entropy goes up when an Event Horizon increases in radius. That means some mass "falling onto" an EH. So this implies, if our universe is actually a 3D EH, both time and increasing entropy can be explained by one thing: Increasing size of our EH. That is, mass falling onto our EH from outside our universe. It also happens to elegantly replace the Big Bang nonsense theory with something that makes sense. It explains the universe expansion as well. Assuming our universe is a 3D EH makes lots of things make sense that don't otherwise make sense.

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

#234

Post by ratorx »

npunt wrote: post #223
ojo-rojo wrote: post #205

Earlier quoted context omitted.

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 :…

Not quite apples to apples tho because you have to take into consideration what was known at the time each theory was developed (the input), not just the output. Theory A: fits 7 known predictions but also makes a not-yet-verified prediction Theory B: fits 8 known predictions and offers no new ones In this example wouldn't Theory A be better, because all else equal it is less likely the product of overfitting and req…

> requires fewer predictions to discover

I don’t think that is implied. It was discovered first, but that doesn’t mean it is necessarily simpler or required less data to discover. Take Newton/Leibniz calculus for example as a clear example of similar discovery time, leading to the same result but using different approaches. Leibniz started after Newton technically, and yet is the preferred way.

Especially if theory B is equivalent to theory A, then using it as a replacement for theory A seems perfectly fine (well as long as there are other benefits).

In some cases it might be pointless though from a scientific standpoint because the goal is “not-yet-known” predictions, but if viewed through a mathematical lens, then it seems like a valid area of study.

Maybe the process behind creating theory A is more generalisable towards future scientific discovery, but that would make the process worthwhile, not the theory.

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

#236

Post by aeonik »

buggyipadmettoo wrote: post #231
aeonik wrote: post #60

Earlier quoted context omitted.

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,…

Just swap out "my take, for what it's worth" For "according to ChatGPT"

I don't like your comment, it's pretty low effort, and your tearing down a lot of effort that I have put into learning about physics and entropy over the years.

I came up with the psuedonym Aeonik Chaos circa 2010 because my studies of Chaos Theory and Entropy left a very deep impact on me.

I've been thinking about entropy ever since my dad, a biochemist, embryologist, and doctor told me he thought that entropy was behind the secret of life. That event was over 30 years ago.

I've been thinking about this stuff very deeply for a very long time.

So no, it's not according to ChatGPT, it's just my current take, but I don't to come out and say "this is how it is", because entropy has a way of being sneaky, I've been wrong about theories of entropy way too many times to pretend to be some authority on the matter.

Hence, this is my take, take it or leave it.

By the way, I love using ChatGPT to learn more about science and math, and have it act as sounding board for ideas. It's great for learning and diving deeper into this stuff.

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

#237

Post by raattgift »

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…

No, here "entropic" is as in the entropic force that returns a stretched rubber band to its unstretched condition, which (as it tends to be scrunched a bit) is at a higher entropy.

https://en.wikipedia.org/wiki/Rubber_band_experiment

"The stretching of the rubber band is an isobaric expansion (A → B) that increases the energy but reduces the entropy"

[apologies for any reversed signs below, I think I caught them all]

In Verlinde' entropic gravity, there is a gravitational interaction that "unstretches" the connection between a pair of masses. When they are closer together they are at higher entropy than when they are further apart. There is a sort of tension that drags separated objects together. In Carney et al's approach there is a "pressure mediated by a microscopic system which is driven towards extremization of its free energy", which means that when objects are far apart there is a lower entropy condition than when they are closer together, and this entropy arises from a gas with a pressure which is lower when objects are closer together than when objects are further apart. Pressure is just the inverse of tension, so at a high enough level, in both entropic gravity theories, you just have a universal law -- comparable to Newton's -- where objects are driven (whether "pulled" or "pushed") together by an entropic force.

This entropic force is not fundamental - it arises from the statistical behaviour of quantum (or otherwise microscopic) degrees of freedom in a holographic setting (i.e., with more dimensions than 3+1). It's a very string-theory idea.

The approach is very hard to make it work unless the entropic force is strictly radial, and so it's hard to see how General Relativity (in the regime where it has been very well tested) can emerge.

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

#238

Post by mhh__ »

emtel wrote: post #158
the__alchemist wrote: post #149

Earlier quoted context omitted.

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.

Jonathan Gorard goes through a handful of testable predictions for the hypergraph stuff here: https://www.youtube.com/watch?v=XLtxXkugd5w

gorard is one to watch

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

#239

Post by analog31 »

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…

Something to consider is that entropy has units of measure. Why would a purely philosophical concept be given units of Joules per Kelvin?

I'm only reminded about this because, though I'm a physicist, I've been out of school for more than 3 decades, and decided that I owed myself a refresher on thermodynamics. This coincided with someone on HN recommending David Tong's textbook-quality lecture notes:

https://www.damtp.cam.ac.uk/user/tong/statphys.html

I think at least the first few pages are readable to a layperson, and address the issue of our imperfect knowledge of the precise configuration of a system containing, say, 1e23 particles.

But if we knew all of those relationships, the system would still have entropy.

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

#240

Post by kgwgk »

Gravityloss wrote: post #221
kgwgk wrote: post #197

Earlier quoted context omitted.

If you saw a comet coming from the sun, or a meteorite coming from the moon, etc. you would also find that suspicious.

Comets are in elliptical orbits around the sun so literally half the time they're traveling away from the sun.

Sometimes they don’t make it:

https://en.wikipedia.org/wiki/Sungrazing_comet

https://www.space.com/8478-comet-collision-sun-captured-3.ht...

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