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A Physicist Who Denies That Dark Matter Exists

cosmos.nautil.us

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Re: A Physicist Who Denies That Dark Matter Exists

#171

Post by lngnmn »

MikkoFinell wrote: post #169
lngnmn wrote: post #167

Earlier quoted context omitted.

Oh, please, cut this cosplay out. In every surgery room of the whole world you could see how chemical compounds administered to patients would turn them unconscious and back. This implies that the consciousness is a product of the brain, not some immaterial substance, divine presence or other kind of abstract crap. This also implies that it is not mere an abstract idea of so-called pure reason ("soul", "I" and "god"…

I didn't ask whether consciousness is abstract crap, nor did I ask about vision subsystems (which aren't even unique to brains), nor did I ask you to explain the whole process of development from fertilized egg to me. Well, unless that has something to do with the experiment that would show that consciousness exists, which it may or may not, at least you drew no apparent connections in your post. I asked you to descr…

> Merely saying that consciousness is a product of the brain is like proving dark matter by saying it's a product of the universe.

This statement is nonsense. The presence or absence of consciousness could be empirically verified and experimentally tested. The presence or absence of dark matter could not be empirically verified because the concept which is referenced by this pair of words belongs to the category of abstract ideas.

Notice, that consciousness is not an abstract idea, it belong to the category of biological processes. You have here a logical error of assuming existence of an abstract concept, which neither could be empirically verified nor experimentally tested.

There is a subtle difference between a product of the physical brain and a product of group-thinking or sectarian beliefs. While the concepts which form the basis of this or that system of beliefs are certainly exist inside the consciousness of the individual believers and certainly are presented in their shared vocabulary, the phenomena which these concepts presumably accurately and completely capture does not exist anywhere in the universe.

Re: A Physicist Who Denies That Dark Matter Exists

#172

Post by dragonwriter »

lngnmn wrote: post #171
MikkoFinell wrote: post #169

Earlier quoted context omitted.

I didn't ask whether consciousness is abstract crap, nor did I ask about vision subsystems (which aren't even unique to brains), nor did I ask you to explain the whole process of development from fertilized egg to me. Well, unless that has something to do with the experiment that would show that consciousness exists, which it may or may not, at least you drew no apparent connections in your post. I asked you to descr…

> Merely saying that consciousness is a product of the brain is like proving dark matter by saying it's a product of the universe. This statement is nonsense. The presence or absence of consciousness could be empirically verified and experimentally tested. The presence or absence of dark matter could not be empirically verified because the concept which is referenced by this pair of words belongs to the category of a…

> The presence or absence of consciousness could be empirically verified and experimentally tested.

No, it can't; there are various behavioral traits that are conjectured to be indicative of consciousness that can be tested, but consciousness itself can either be tested nor observed in anyone except the observer.

> Notice, that consciousness is not an abstract idea, it belong to the category of biological processes.

No, consciousness is not a biological process, it's a phenomenon which is assumed to occur as a product of biological processes, though it's often conjectured that it could also occur as a product of other processes as well.

Re: A Physicist Who Denies That Dark Matter Exists

#173

Post by lngnmn »

dragonwriter wrote: post #172
lngnmn wrote: post #171

Earlier quoted context omitted.

> Merely saying that consciousness is a product of the brain is like proving dark matter by saying it's a product of the universe. This statement is nonsense. The presence or absence of consciousness could be empirically verified and experimentally tested. The presence or absence of dark matter could not be empirically verified because the concept which is referenced by this pair of words belongs to the category of a…

> The presence or absence of consciousness could be empirically verified and experimentally tested. No, it can't; there are various behavioral traits that are conjectured to be indicative of consciousness that can be tested, but consciousness itself can either be tested nor observed in anyone except the observer. > Notice, that consciousness is not an abstract idea, it belong to the category of biological processes.…

Yes, consciousness is a product of various behavioral traits, but its presence could be empirically tested. There are simple quick medical procedures which could tell whether a man (or even a dog) is conscious or not, and there is an ultimate test in a fMRI scanner which could prove that the patient has no consciousness. Any religious nonsense about validity of the fMRI test is plain stupidity.

Some limited artificial consciousness is obviously possible, even artificial self-consciousness, at least in theory. But possibility does not imply existence.

Re: A Physicist Who Denies That Dark Matter Exists

#174

Post by SagelyGuru »

SagelyGuru wrote: post #15

There is another possible explanation instead of dark matter and that is electric charge and currents (plasma flows). Electric force is many orders of magnitude stronger than gravity. So, if the objects in the universe are charged, the repelling force between them could account for the expansion acceleration in a very simple way.

Anyway, thank you for the predictable downvotes. At least I know how Galileo felt when downvoted for his non-standard explanation. "And still it turns!" I am afraid that I remain similarly unconvinced by appeals to the authority of the "experts in the field". At least "the experts" in Galileo's days did not keep inventing new invisible things, except for the angels on the point of a needle. This made their theory more stable and, some may say, more credible, than dark matter.

Re: A Physicist Who Denies That Dark Matter Exists

#175

Post by MikkoFinell »

lngnmn wrote: post #171
MikkoFinell wrote: post #169

Earlier quoted context omitted.

I didn't ask whether consciousness is abstract crap, nor did I ask about vision subsystems (which aren't even unique to brains), nor did I ask you to explain the whole process of development from fertilized egg to me. Well, unless that has something to do with the experiment that would show that consciousness exists, which it may or may not, at least you drew no apparent connections in your post. I asked you to descr…

> Merely saying that consciousness is a product of the brain is like proving dark matter by saying it's a product of the universe. This statement is nonsense. The presence or absence of consciousness could be empirically verified and experimentally tested. The presence or absence of dark matter could not be empirically verified because the concept which is referenced by this pair of words belongs to the category of a…

> The presence or absence of consciousness could be empirically verified and experimentally tested.

How?

> consciousness is not an abstract idea, it belong to the category of biological processes.

Okay, describe the experiment which can prove that you are justified in making such statements.

Re: A Physicist Who Denies That Dark Matter Exists

#176

Post by pja »

pka wrote: post #36
pja wrote: post #21

Earlier quoted context omitted.

(I have a physics degree, but it’s very rusty at this point) Particle physics has a long history of noticing gaps in the experimental data that don’t match up with current theories and positing that maybe a new particle would solve the problem. This goes right back to things like the neutrino (which was posited to preserve momentum in certain particle interactions IIRC) and even the neutron. Sometimes the suggestion…

My impression was that QFT includes gravity and "only" breaks down when things get extreme, i.e. black holes/big bang/etc.

No, there is no quantum theory of gravity & QFT doesn’t include gravity at all. The best you can do is add gravitational effects as an after-thought, but the things you might analyse with the full QFT are generally far too small & short lived for gravitational effects to matter anyway.

Re: A Physicist Who Denies That Dark Matter Exists

#177

Post by mitchty »

jack9 wrote: post #116
mitchty wrote: post #19

Earlier quoted context omitted.

We already observe it via its gravitational effects on galaxies. Additionally, good luck getting "fixed equations" to agree with the reams of data.

Isn't that what MOND is doing, to some degree?

From what I have looked into, it breaks down with observed things on the fringes, aka black holes and supercluster type stuff.

This is the "silver bullet" if you will for a lot of these theories: https://en.wikipedia.org/wiki/Bullet_Cluster

It would be great if "just" modifying the equations works. But it has an uphill climb against observed data.

Re: A Physicist Who Denies That Dark Matter Exists

#178

Post by raattgift »

platz wrote: post #137
nialv7 wrote: post #136

Earlier quoted context omitted.

Particle is an excited state of a field. What you are saying is the exact same thing.

Yes, this misses the point i'm making however - I think fields connote more than just the "excited state" part (the particle). Particles aren't exactly the same idea because they don't explain the coupling between fields, or things like 'virtual particles' which don't "count" as real particles but have important real behaviors of the field itself.

The problem is that your "lens" statement doesn't convey much information; if it goes deep, unfortunately it's not obvious. For example, it doesn't tell anyone whether you think that CDM is sparticles or a quantization of a function on the Ricci scalar or of a second metric or whatever.

The latter two are awfully hard to distinguish from relativistic approaches to MOND; indeed you could quantize most of the approaches in Chapter 7 of https://arxiv.org/abs/1112.3960 .

More generally, you can put a scalar or other degree of freedom on either side of the usual write-down of the Einstein Field Equations - on the R side it's "modified gravity", but on the T side it's "modified matter". There's no strong reason to choose one side over the other (Einstein and Schrödinger had a couple of letters to each other about "which side" as early as 1918![1]).

Either way you're adding a field to General Relativity -- and you'd see that in a Langrangian formulation like an expansion of the Einstein-Hilbert action[2]. There is no real reason that you couldn't quantize a field on either side of G = T (consider how g is quantized in perturbative quantum gravity, for example), and if they couple at all non-gravitationally to standard model particles, you'd very much want to.

Finally, historically, particle CDM was strongly motivated by QFT considerations in the first place, with the expectation that they would be lightest MSSM sparticles or mass-explaining sterile neutrinos on the WIMP hand, or alternatively strong-CP resolving axions. So your "lens" is standard, so I agree with your parent comment.

Lastly, you wrote essentially the same comment several days ago https://news.ycombinator.com/item?id=13600085 .

[1] https://arxiv.org/abs/1211.6338

[2] e.g. S = \int \left[ 1/2 R + \mathcal{L}_{baryons} + \mathcal{L}_{photons} + \mathcal{L}_{neutrinos} + \mathcal{L}_{CDM} + ... \right] \sqrt{-g} {d}^{4}x.

Re: A Physicist Who Denies That Dark Matter Exists

#179

Post by raattgift »

ajross wrote: post #153
dogma1138 wrote: post #75

Earlier quoted context omitted.

We've seen instances already where gravitational lensing was explained through other means (very dim clusters, dust, and even camera issues), we also don't know if the space time on those scales is "smooth", if it isn't then light will not travel in a straight line which would account for the lensing effects. The spacetime curvature, mass/energy, and gravity have quite a few interesting interactions as in gravity as…

> we also don't know if the space time on those scales is "smooth", if it isn't then light will not travel in a straight line which would account for the lensing effects. Except space isn't perfectly smooth. It does curve, and that curvature is gravity. That's what general relativity is all about. If you want to postulate some way for the universe to curve absent observable mass, go ahead: you're doing nothing but re…

> If you want to postulate some way for the universe to curve absent observable mass

The de Sitter vacuum is an exact solution to the Einstein Field Equations of General Relativity that does exactly that.

Our expanding universe will very likely closely approximate de Sitter space in the extreme far future.

There are many other vacuum solutions; it's normal in General Relativity to think of curvature as being a background laid down by hand (ideally approximating nature) and then perturbing that background with matter or probing it with test particles.

> Except space isn't perfectly smooth.

General Relativity is defined on a smooth (infinitely differentiable) manifold.

This is very important! https://en.wikipedia.org/wiki/Smoothness

There can be arbitrary curvature in the manifold, however, and unfortunately with the Einstein Field Equations you can pretty easily produce manifolds with curvature singularities, and those are manifestly not smooth (and that is one driver for research aiming to extend General Relativity).

But to the first order, your experience of gravitation near the surface of the Earth emerges from the very weak manifold curvature the planet and its microscopic components and their motions source. The nearest strong curvature is a couple of kiloparsecs away.

Re: A Physicist Who Denies That Dark Matter Exists

#180

Post by raattgift »

jerf wrote: post #13
roryisok wrote: post #3

> "If Newtonian physics can’t predict the fixed curves, perhaps we should fix Newton, instead of making up a whole new class of matter just to fit our measurements." I've always felt this way about dark matter, but as a lay person with no background in physics, it's an opinion I'm hesitant to express. if you have a model that predicts something, but the prediction is off by several orders of magnitude, the model is w…

One of the mental problems that I think people get in this area is that you can't help but mentally imagine that there's just these few points of data that we need to hit, and so we have a lot of freedom in how to construct formulae that match the observation, so why are scientists being so obstinate about the possibility that MOND may be true? But that's not the case. We have petabytes of data from space (if not mor…

> I've seen people create variants of MOND that try to address the Bullet Cluster problem, but you start having to have some sort of really weird gravity memory effect in space or something, where space itself "remembers" that it used to have a lot of matter in it and still has a small amount of gravitation in it despite no longer containing the corresponding mass

Which variants are these?

cf. section 8.3, https://arxiv.org/abs/1112.3960

Several of the relativstic MOND theories (see chapter 7 of the same review) are detailed, and I don't see how any of the 8.3 set matches the quote above.

It's already a few years old, though, so maybe you've seen something newer.

> We also have a Standard Model of particle physics that, whatever its known flaws may be, doesn't immediately obviously have a hole for dark matter in it

There's a hole in chirality, which was part of the motivation for WIMPs as CDM.

There's a hole in the Strong-CP problem, which was part of the motivation for axions as CDM.

There's a hole in the hierarchy problem, also part of the motivation for WIMPs but also the motivation for Little-Higgs-like CDM.

Those particle dark matter candidates came from BTSM gauge theorists, not relativists.

> I also am sympathetic to MOND solutions as well.

If you make MOND relativistic you wind up adding a field to G = T; which side it's on doesn't really matter - it'd mostly be either down to an aesthetic choice based on coupling strength, or social considerations (this goes back to at least 1918! [1]).

[1] https://arxiv.org/abs/1211.6338 (and sure enough even in 2017 you will not be arrested by the EFE police if you put the cosmological constant onto the T side as a source, and you might even want to, e.g. in quintessence modelling, or in the cosmological frame; also cf. the choice between the Einstein frame and the Jordan frame for scalar-tensor gravity)

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