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Dark Matter Is Even More of a Mystery Than Expected
schwit1 writes: Using the Hubble and Chandra space telescopes astronomers have discovered that dark matter is not only invisible to direct observation, it is invisible to itself! Quoting: "As two galactic clusters collide, the stars, gas and dark matter interact in different ways. The clouds of gas suffer drag, slow down and often stop, whereas the stars zip past one another, unless they collide — which is rare. On studying what happens to dark matter during these collisions, the researchers realized that, like stars, the colliding clouds of dark matter have little effect on one another. Thought to be spread evenly throughout each cluster, it seems logical to assume that the clouds of dark matter would have a strong interaction — much like the colliding clouds of gas as the colliding dark matter particles should come into very close proximity. But rather than creating drag, the dark matter clouds slide through one another seamlessly." The data here is on the very edge of reality, built on too many assumptions. We know that something undetected as yet is influencing the motions of galaxies, but what exactly it is remains completely unknown. These results only make the mystery more mysterious.
Isn't this what one would expect if dark matter is WIMPs?
"99 dead duelists of Dios on the wall. 99 dead duelists of Dios! Take one's ring, pass it around..."
Ahem; that's "Matter of Color", thank you very much.
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If there is a vacuum in space, would their need to be a corresponding antivacuum?
No. Because of Heisenberg's uncertainty principle, there can never be a complete vacuum. Even if there was, you couldn't measure it without destroying it.
isn't there a good chance that the dark matter theory is incorrect, and was created to account for an error in certain physics equations? Mb dark matter is so invisible because it doesn't actually exist?
It really bothers me to see quotes like this one: "There is more dark matter in the Universe than visible matter, but it is extremely elusive."
That's so matter of fact, and leaves no room for the possibility that the theory of dark matter is wrong. I feel that the certainty level around our understanding of this topic is low enough that it isn't fair to competing theories to say things like that as if they are observed fact. In fact, we've never detected dark matter. We infer its existence from a number of things that don't add up gravitationally without it, indicating we're missing something. Dark matter that interacts gravitationally allows us to model a universe that adds up, if only this invisible stuff were distributed just so.
This article shows yet another data point indicating that dark matter may not exist, because of how it continues to not react with stuff, just as it would if it weren't there at all. I don't mean to say that it's 100% wrong, but I think it's unfair to say with 100% certainty that it's true either. Shouldn't we as scientists be more careful with our words, and say that dark matter is BELIEVED to make up more of the universe than does visible matter, based on our current leading theories? I think being careful with what we know and how well we know it is important to maintaining trust with the public and with each-other.
--Jaborandy
We're trying to explain inflation and the motions of stars orbiting galaxies not matching our naive model.... couldn't a non-linear gravity model explain all this without the dark energy/matter hocus pocus?
Sure, but that would involve even greater hocus pocus than the current theory and fails at explaining other observations. So far, trying to come up with any hypothetical explanation involving MOND has been so complex that nobody has been able to come up with one that explains even the rotation of galaxies. If you or any other person could come up with a good law of nonlinear gravity that works, even if it completely fails at any of the other observations, there's a paper in a prestigious journal and some physics cred for you.
Thought to be spread evenly throughout each cluster, it seems logical to assume that the clouds of dark matter would have a strong interaction
It would actually be completely illogical to assume that precisely BECAUSE Dark Matter is spread evenly through each cluster. If it had a strong self interaction then, just like matter, it would bump into itself and coalesce into clumps just like that other strongly, self interacting stuff we call matter. The fact that Dark Matter has a completely different mass distribution than ordinary matter is clear evidence that it does not have a large self interaction cross-section...and we have had direct evidence of this since the Bullet Cluster was discovered.
It's always nice to have more confirmation but since another recent story on the same site was talking about the "new" possibility of invisible Higgs decays to Dark Matter particles (something we looked for 15+ years ago at the Tevatron as well as the previous Run 1 of the LHC) I have to wonder if the writers of the site have suffered extreme time dilation for the past decade or two.
This.
Consider that for two stars to hit each other, they essentially have to pass within one stellar diameter of each other (absent gravity, but they're moving at over escape speed relative to each other, so gravity won't enlarge that distance a whole hell of a lot).
So, one stellar diameter is ~1.4 Gm for Sol. Nearest star is 40,000,000 Gm away. If that nearest star were headed toward us (it's not), it's course would have to be within 0.01 seconds of arc of our Sun in order to actually hit it.
And stars farther away have an even smaller course window to be in to smack us....
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Dateline: Millions of light years (even faster parsecs than the Kessel run)
Lede: Scientists in the Dark; Does it Matter?
Today scientists announced that they can't see anything happening with stuff they can't see, but think is there, because otherwise the math is no good. After receiving directions to his laboratory on the phone, I went to see an authority on dark matter. During the interview, Dr. Seemore Lichspittle told this Any Paper, Any Time reporter that the thing about dark matter that one has to understand is that "it goes to eleven." When confronted with the observation that the sensing instruments only had scales from 0-10, he responded "Yes, yes, that's exactly it. The numbers... the numbers only work out in the dark. When the instruments are off. Matter of fact, it's all dark, really." At that point the interview was cut short as two lab assistants in white coats hustled Dr. Lichspittle into his own custom white lab jacket. Late for an important meeting, no doubt. As he left, nodding, he called back "it's really quite dark." Food for thought! Leaving Arkham, I was struck by the picturesque beauty of the stonework, and very appreciative of the tight security. We can rest easy, knowing that national treasures like Dr. Lichspittle work in such a safe enviroment.
I've fallen off your lawn, and I can't get up.
There have been several theories built on that assumption, most prominently one called MOND (MOdified Newtonian Dynamics), but more recently one that builds on relativity rather than Newtonian gravity/dynamics.
But none of these theories (hypotheses?) have gained much acceptance from the physics community, as far as I know.