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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?
Indeed. I don't think that any of this is new. The reason dark matter was hypothesized in the first place was because of the behavior of colliding galaxies, such as the Bullet Cluster. The missing mass couldn't be stars, because it didn't emit light, it couldn't be gas or dust, because it didn't experience drag, so it must be either WIMPS or MACHOs. Further observations ruled out the MACHOs. So what is new about this observation?
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
Here some someone with a propeller beanie on his head will tell me that dark matter must exist because "math"... which is fine only "math" is not actually evidence of something being there absent emperical evaluation because even if the numbers add up a certain way so do orbital epicycles.... and they were bullshit.
A pitfall of the "math" argument is that if you have some very clever people come up with some very clever theories they can confuse Tolken-like world building with "reality".
The justification for dark matter is unexplained gravity. And the gravity is something we know exists because we are seeing the speed at which galaxies spin around and there shouldn't be enough mass to explain that speed. And that extra mass because we can't find it is called "dark matter"...
Well, that's great... only that doesn't mean dark matter exists. It could mean our theories of gravitation are wrong or any number of other things.
same thing with "Dark energy"... which in so far as I've figured out only exists because galaxies are accelerating away from each other and we have no idea what could cause every galaxy to propel itself at speeds like that except some other unexplained energy and that's what is dark energy.
In both cases it just sounds like they don't have enough observational data to really have a valid cosmological model. And I would much rather them make that admission then talk to me about "dark" whatever.
I've decided to stop wasting my time responding to AC trolls/sockpuppets... so if you want a response from me... login.
Dark energy is just the latest name for the Cosmological Constant
You know, I'm as happy as anyone else that physicists have been able to do so much with their models, but what kind of navel-gazing mathurbation is this?
Dark energy is an observed physical phenomenon.
The cosmological constant is a term in an equation. It's a very good equation, mind you, but a lot of very good equations have later turned out to be wrong or good for only a special class of phenomena. Equations can predict, but they don't prove anything. It's also worth noting that the cosmological constant was supposed to predict a force that would hold the universe together. Dark energy is a force that is tearing the universe apart. Someone clever pointed out that hey, that works if you just flip the sign of the cosmological constant but I'm not sure I'd call that a win.
And regardless, I don't think it's reasonable to imply that the territory is imitating the map.