Entropy and Symmetry

https://www.nature.com/articles/s41598-019-46765-w

by squidproquo • 7 years ago

14 6 7 years ago

nature.com

squidproquo• 7 years ago

Here is a link to a news article that less technical: https://www.newsweek.com/milky-way-dark-matter-kepler-145323...

credit_guy3• 7 years ago

This is either quackery or a Nobel prize worthy breakthrough. I'm inclined to go with the first.

Basically they say they can explain the galaxy rotation speed problem using some novel concepts of entropy and information instead of traditional explanation involving dark matter. If they are right, this will bag them a Nobel prize with 100% certainty.

But I'm afraid they aren't right.

* neither author is an astrophysicist

* one's interests are [1] :"Current interests include flexgrid & elastic optical networking technologies (subsystems & devices) & architectures, converged wireless-wireline access networks (5G), theory of information & entropy, cryptography & security."

* the other author describes his interests as follows [2]: "My own interest is accurate ion beam analysis (including RBS and PIXE) using a 2MV Tandem"

* 5G networks and ion beams don't have much in common with cosmology

* the second author is also considered a Biblical scholar [3]. Here's one little glimpse into how he understands the world: "The Kingdom is about the return of the glory of God. Which widgets you have in your pocket is hardly relevant to that."

[1] https://www.researchgate.net/profile/Michael_Parker12

[2] https://www.researchgate.net/profile/Chris_Jeynes

[3] https://www.churchtimes.co.uk/articles/2018/8-june/features/...

FiatLuxDave2• 7 years ago

Judging a paper by the background of the authors is a sure sign that you were not able to read the paper and understand it. There is no actual astrophysics in this paper, only Lagrangian mechanics, geometrical algebra and information theory. Anyone who works with ion beams uses Lagrangian mechanics. Anyone who works with rf networks uses information theory. So, I'm not sure why their backgrounds would be a problem here. And seriously, holding someone's mainstream religious beliefs against them? That's just plain uncivil. I apologize if this is harsh, but I think that responding here is better than just downvoting you.

All that said, I agree with a part of your assessment, but for other reasons. The crux of the paper is a transformation from Lagrangian mechanics (in other words, the motion of particles with no frictional forces) into a form of 'entropic mechanics' used for calculating the entropy of a certain configuration of particles. They defined this transformation using a coordinate system which matched the spiral/helical shape that they were focusing on (see Eq 9a). In a way, this is a bit of a cheat, because had they used a fixed cartesian coordinate system I suspect the model would produce highest entropy when particles aligned with the x,y,z axes.

However, the interesting part of the paper is where they make an independent prediction of the energy to change B-DNA to p-DNA. This is the only non-tautology prediction in the paper, and it is interesting that their model gives a prediction close to the measured value. This means that their alternate 'entropic mechanics' means of calculation might be useful because it could simplify complex calculations.

The galactic stuff is basically a tautology. First, they are only calculating shape, and not doing anything with the velocity distribution (which is where the dark matter problem comes from). They say that most of the entropy is in the SBH in the galactic center, but then when they try to calculate the temperature of the remaining galaxy, they make a stability assumption that just happens to give the galaxy a thermodynamic structure which matches their spiral form (section right before eq 27a). Amazingly, this give a maximum entropy when the galaxy has a spiral structure!

So, from reading the paper only once, my assessment is a) this method could be useful for calculating entropy for particles in fixed geometries, b) the galaxy stuff is crap.

credit_guy3• 7 years ago

Judging a paper by the background of the authors is a sure sign that you were not able to read the paper and understand it.

Reading a paper requires some effort. The more familiar you are with the topic, the less effort you invest, but the effort is there.

It's valuable then to apply some heuristics to decide if a paper is worth reading or even skimming. One such heuristic is if the paper makes it to the front page of HN, or, say, if it's published in Nature. Based on this, a lot of people could waste some time they better spend doing something else.

If someone comes and points out some red flags, that's a service to the community. That service comes at a risk to one's own karma, as it's threading the boundary of what the HN community thinks is good discourse (for example the charity principle). Pointing out red flags without pointing out actual errors in the papers can be easily equated with ad-hominem attacks (believe me, I thought ten times before deciding about quoting the second author's thoughts on God).

I still decided that this is a good case to put my karma at risk: the claim that some new information-entropy force can explain the missing mass in the Universe is too important to ignore.

That said, your more informed analysis obviously adds much more value than my superficial one, so thank you for that.

Entropy and Symmetry

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