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Could dark matter not exist?

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Re: Could dark matter not exist?

#21

Post by jfoutz »

lordnacho wrote: post #4

It reads like a great example of how theory works. You have some evidence (old planets), and a model that predicts it well (Newton/Kepler). Then some new evidence comes in (Uranus), and the theory is almost right, but not quite. So we modify it a little, or we start searching for an extra mass to explain the error. Then some more experimental evidence comes in (galactic radial velocity), and we are thinking about mod…

Real science is ugly because there are a bunch of theories that kinda sorta fit, but not really well. I think Maxwell had something like 40 equations for electricity. Give it a hundred years and hundreds of thousands of grad student hours, and something quite clean emerges.

The unknown edges are messy, but as competing theories get winnowed out, merged and refined they become clear and concise.

Re: Could dark matter not exist?

#22

Post by AnimalMuppet »

jfoutz wrote: post #21
lordnacho wrote: post #4

It reads like a great example of how theory works. You have some evidence (old planets), and a model that predicts it well (Newton/Kepler). Then some new evidence comes in (Uranus), and the theory is almost right, but not quite. So we modify it a little, or we start searching for an extra mass to explain the error. Then some more experimental evidence comes in (galactic radial velocity), and we are thinking about mod…

Real science is ugly because there are a bunch of theories that kinda sorta fit, but not really well. I think Maxwell had something like 40 equations for electricity. Give it a hundred years and hundreds of thousands of grad student hours, and something quite clean emerges. The unknown edges are messy, but as competing theories get winnowed out, merged and refined they become clear and concise.

Maxwell had 20 equations for electromagnetism, because he didn't use vector notation, so he had to do the equations component by component. But that had nothing to do with having multiple theories. The current "Maxwell's equations" are exactly the same as Maxwell's 20 equations, merely expressed in a more convenient form.

Re: Could dark matter not exist?

#23

Post by AnimalMuppet »

rcxdude wrote: post #6
dandelany wrote: post #5

Earlier quoted context omitted.

Alternatively: The orbits around galaxies fail to follow the law of gravity of ordinary matter. The orbits are as if our gravity calculations, which seem to work well otherwise, are flawed. Something in/near galaxies causes them to bend light as if gravity were different. So, for that region, call it a flaw in the theory of gravity. Seems simple enough. "Unseen, never-before-detected form of matter which doesn't inte…

Yeah, but AFAIK all the explanations based around adjusting our theory of gravity have failed to match the results, and tend to be pretty complicated and thus prone to overfitting.

Whereas, since you can adjust the hypothetical distribution of dark matter to be whatever you need it to be to fit the data, you cannot falsify dark matter this way, since proving that no possible distribution of dark matter could fit the evidence is pretty much impossible.

Still, to me there seems to be some level of equal implausibility in saying "our theory of gravity is wrong" and in saying "our theory of matter is wrong".

Re: Could dark matter not exist?

#25

Post by Retra »

mixmastamyk wrote: post #7

Interesting, I always thought of dark matter as just a lot of extra "dust", the dust that clumps to make the stars that make up the universe. The asteroid belt, the extra mass in our kuiper or oort clouds, etc. The dust that blocks parts of our view of the Milky way. This article (and others I'm now skimming) point out that dark matter needs other magical properties however. Why is that the case? Why does simple "dar…

Like others said: dust simply isn't dark. At least not in the way implied in the term 'dark matter'.

Re: Could dark matter not exist?

#26

Post by cristianpascu »

gnufied wrote: post #20
HillOBeans wrote: post #18

For those who are interested, physicist John Hartnett has developed a model that does not require dark matter. His work builds on that of Moshe Carmeli, who published "Cosmological Special Relativity". Hartnett's book is "Starlight, Time, and the New Physics" ISBN 978-0-949906-68-7. Disclaimer: I am not a physicist, and the math is way over my head, so I cannot double-check it. Hartnett has not made much, if any, hea…

Just read one of his articles from his Website. He mixes physics and mythology with impunity. No wonder, his theories are not taken seriously.

So, say, if someone comes to you with a clean demonstration of how and why something is happening in the world, people verify it and it proves correct, and (s)he says the idea was revealed while smoking pot in a mystical hotel in north canada, or france for that matter, you'd say no one should take the theory seriously? Good job!

Re: Could dark matter not exist?

#27

Post by Retra »

AnimalMuppet wrote: post #23
rcxdude wrote: post #6

Earlier quoted context omitted.

Yeah, but AFAIK all the explanations based around adjusting our theory of gravity have failed to match the results, and tend to be pretty complicated and thus prone to overfitting.

Whereas, since you can adjust the hypothetical distribution of dark matter to be whatever you need it to be to fit the data, you cannot falsify dark matter this way, since proving that no possible distribution of dark matter could fit the evidence is pretty much impossible. Still, to me there seems to be some level of equal implausibility in saying "our theory of gravity is wrong" and in saying "our theory of matter…

We have much more experience with matter, because we can interact with it on a variety of scales in a lab. Gravity is much harder to interact with, and thus much harder to explore. That's why it is quite a bit more likely that our understanding of gravity is incorrect.

Re: Could dark matter not exist?

#28

Post by cletus »

I'm no physicist but I've asked myself this question. It's a bit like string theory. String theory is a mathematical answer that solves some (all?) of the inconsistencies between quantum theory and gravity but has some implications that have no experimental evidence (eg extra dimensions).

Dark matter always struck me as a kludge to explain the universe fit our model. There are many theories on it but no observed or experimental effects of dark matter to date.

We say that there are four fundamental forces in the universe: weak nuclear, strong nuclear, electromagnetism and gravity. The first three are pretty adequately explained by quantum mechanics (AFAICT). The last of course isn't but is described pretty darn well by relativity.

Thing is, what's always struck me as odd is the other forces, I believe, can both attract and repel. There is no observation or experimental evidence of "antigravity".

It has always made me wonder if we're not making an error by trying to fit gravity into the Standard Model. Perhaps it's not a force like the others are and simply the result of the nature of space-time.

Anyway, like I said: complete layman here. What I'm saying might be completely nonsensical to anyone with half a clue about physics.

I know the LHC has looked and is looking for any evidence at the edges of the Standard Model of some violation that will hint at something that might explain all this. I also know minds far brighter than mine have spent a lot of time thinking about this.

I'm still left wondering if dark matter/energy isn't simply another "string theory".

Re: Could dark matter not exist?

#29

Post by GFK_of_xmaspast »

HillOBeans wrote: post #18

For those who are interested, physicist John Hartnett has developed a model that does not require dark matter. His work builds on that of Moshe Carmeli, who published "Cosmological Special Relativity". Hartnett's book is "Starlight, Time, and the New Physics" ISBN 978-0-949906-68-7. Disclaimer: I am not a physicist, and the math is way over my head, so I cannot double-check it. Hartnett has not made much, if any, hea…

Look at the first graph in the "My own analysis" section here: http://johnhartnett.org/2015/03/29/the-coming-long-dark-wint... and laugh.

Re: Could dark matter not exist?

#30

Post by cristianpascu »

I graduated physics, but I'm almost a layman when it comes to general relativity. Still, I wonder if another possible explanation for stuff that don't match theory could be the basic assumption about our current cosmology. That the space is flat where there's no matter. Since there's a relation between the geometry of the space and the matter within, would it be unreasonable to believe that space itself could be curved independently of the matter we can observed? Maybe for other reasons, yet unknown?
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