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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

#61

Post by roryisok »

mikeash wrote: post #52
fuhrysteve wrote: post #4

Earlier quoted context omitted.

> 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. I have always had the same inclination. It seems like a classic candidate for using Occam's razor. Would love to hear someone who knows more about physics weigh in with a more nuanced viewpoint.

If you're looking at the sky and there appears to be a lot more stuff there than just the bits that emit light, wouldn't Occam's Razor suggest that the presence of more stuff is the most natural explanation, rather than rejiggering the fundamental laws of physics?

It's more like you're looking at the sky and what you can see doesn't weigh as much as it should. Does Occam's Razor suggest that there's invisible stuff? or that you're weighing stuff wrong?

Re: A Physicist Who Denies That Dark Matter Exists

#62

Post by dahart »

fuhrysteve wrote: post #4
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…

> 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. I have always had the same inclination. It seems like a classic candidate for using Occam's razor. Would love to hear someone who knows more about physics weigh in with a more nuanced viewpoint.

What does Occam's razor say about a contradiction?

If two things that are observably exactly the same behave differently, then what should one conclude is the simplest explanation?

If you look in a telescope for a year, and notice that an apparently free-floating star out in the galaxy with no neighbors is taking a sharply curved path and everything else in the sky is going basically straight, you have two choices: 1) either something you can't see yet is there and acting on the star, 2) conservation of momentum, and the law of equal and opposite reactions need to be thrown out because they're wrong, and we need to start from scratch with physics.

Which of those two would Occam say is more likely?

Re: A Physicist Who Denies That Dark Matter Exists

#63

Post by mikeash »

roryisok wrote: post #61
mikeash wrote: post #52

Earlier quoted context omitted.

If you're looking at the sky and there appears to be a lot more stuff there than just the bits that emit light, wouldn't Occam's Razor suggest that the presence of more stuff is the most natural explanation, rather than rejiggering the fundamental laws of physics?

It's more like you're looking at the sky and what you can see doesn't weigh as much as it should. Does Occam's Razor suggest that there's invisible stuff? or that you're weighing stuff wrong?

Except it's not, because the "missing" mass is not distributed in the same way as the stuff that emits light. Some places have a lot more "missing" than others.

Re: A Physicist Who Denies That Dark Matter Exists

#64

Post by davrosthedalek »

waqf wrote: post #58
jerf wrote: post #13

Earlier quoted context omitted.

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…

> What's true is true, regardless of how we feel about how beautiful it is. I think that's, in a certain sense, not really correct. Without some form of Occam's Razor, you can't do science — or at least, you can't come to any definite conclusions, because there are always infinitely many models that would explain any observation. Turning that around, it means that for any fixed amount N of data in support of your hyp…

You can reason about classes of theories instead of theories, and then rank them. "Ugliness", as you write, might be one of the ranking criteria, but there are others, for example "predictiveness".

Re: A Physicist Who Denies That Dark Matter Exists

#65

Post by throw_away_777 »

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…

The models of the universe with and without dark are fundamentally different, it is not inventing "invisible stuff to explain that the model is still right". The nature and composition of fundamental particles are an integral part of models of the universe. There is also a long track record of predicting the existence of particles and then later discovering these particles, for example the Higgs boson. Of course far more particles have been predicted and not (yet) discovered, such as theories of super-symmetry, but these predictions usually don't have the same type of consensus that the Higgs or dark matter has. While dark matter is invisible in the classical sense, it is observable by its gravitational effects. We have also observed what looks like clumps of dark matter, which modified theories of gravity have great difficulty explaining. With that said, until someone actually experimentally observes dark matter it is still a theory and could well be wrong. But this is true of all competing theories - there is no experimental evidence for theories other than dark matter.

Re: A Physicist Who Denies That Dark Matter Exists

#66

Post by badosu »

michaelbuckbee wrote: post #16
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…

There used to be this theory of Phlogiston, which was a material substance of heat (if you put a lit match under a brick, phlogiston would move from the match to the brick.) Today of course, this sounds ridiculous. But my physics teacher was always keen to point out that the people involved weren't stupid and that it was an important theory because it was a good starting mental model of how things actually worked and…

This also reminds me of the Michelson-Morley experiment[0].

A pretty sofisticated setup (at the time) was preparated to prove the fairly established idea that light propagated through Aether.

Well, the failure of the experiment motivated a lot of scientists to improve and test other models.

I can't exactly recall right now, but Einstein's work was supported by the work of many other scientists.

It's not the case that at the time an alternative theory of gravity, space and time was unpopular, as you can see in the works of Lorentz and Minkowski for example.

Not to degrade Einstein's contribution, but to shed light on how the actual scientific process diverges from the popular perception (even among fairly educated people).

In quantum mechanics and analyzing the history of it's development this is much more evident. E.G. Max Planck on his solution to the Ultraviolet Catastrophe[1]: "My unavailing attempts to somehow reintegrate the action quantum into classical theory extended over several years and caused me much trouble."

0: https://simple.wikipedia.org/wiki/Michelson%E2%80%93Morley_e...

1: https://en.wikipedia.org/wiki/Ultraviolet_catastrophe

Re: A Physicist Who Denies That Dark Matter Exists

#67

Post by misnome »

d3ckard wrote: post #8
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…

Same feelings here. I genuinely do not understand how adding unobservable objects would be the right approach instead of just fixing the equations.

Because every other observation for hundreds of years is explained perfectly by "The equations", so you need to "Fix" them in a way that doesn't change any of the existing answers.

And yes, as Cozzyd points out, matter is actually part of these equations. The simplest changes involve adding an extra term to the equation with such-and-such properties that disappear in the normal cases - that is dark matter.

Re: A Physicist Who Denies That Dark Matter Exists

#69

Post by M_Grey »

chopin wrote: post #50

Afaik there is strong support for dark matter via gravitational lensing effects of galaxies. Unfortunately it is not mentioned in the article whether MOND can cope with these observations. At least I would expect that there might be some integration of MOND into ART which explains that.

Increasingly, observations like the ones you mention, along with galaxy rotation curves and more, have really narrowed down the space that DM can occupy. MOND in particular has only very narrow ranges with which it can remain sound, and increasingly it requires modifying the modification to keep that.
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