Hubble Telescope Maps Dark Matter in 3D

dido writes "The BBC reports that the Hubble Space Telescope has been used to make a map of the dark matter distribution of the universe, providing the best evidence of the role dark matter plays in the structure and evolution of the universe. From the article: 'According to one researcher, the findings provide "beautiful confirmation" of standard theories to explain how structures in the Universe evolved over billions of years.'"

Comments

dark matter does not exist

[ars]

"beautiful confirmation" of standard theories?????

What standard theories? Dark matter does not exist, as least not as far as anyone (except astronomers with good imaginations) knows. There is a very nice (and complete!) standard model of physics, and dark matter holds no place.

I should qualify, I'm talking about theroes of non-baryonic dark matter and even worse dark energy.

Regular matter, that is simply dark - i.e. cold, and not emiting light, does not bother me. But making up particles no one has ever seen just because you don't understand what you are seing is fitting facts to the data.

Scientists often discuss new theories, etc, and in that context dark matter has it's place, but to claim it exists - as this story does - without being able to actually measure anything is quite silly and premature. If you don't understand something, say so, don't invent plausable explanations that have nothing supporting them except your lack of knowledge.

Re:dark matter does not exist

[ceoyoyo]

Isn't that exactly what they did? They measured mass distributions through gravitational lensing and noted the places where there was more apparent mass then there should be. You can theorize that gravity works strangely at large scales, and inconsistently too, since they found clumps, but the simplest explanation that matches the observations is that there is something with mass that we can't see. It might be normal matter, but the fact that there's an enormous amount of it and it somehow avoids rubbing together and getting hot like all the other matter we know of is problematic. When galaxies collide it also seems to just keep on going while the normal matter slows down when it hits something going the other direction. Given those two observations (dark and appears not to interact other than gravitationally), a subatomic particle isn't so bad an explanation. It's not so far fetched either -- we know of other particles that have those properties. They're called neutrinos.

Re:Does Dark Matter exist?

[calice]

This is what I don't get about dark matter, and this is just how I see it, and no one has ever given me a decent explanation. Why is it that scientists think that dark matter exists simply because the observed galaxies don't conform to Newton's Laws? Wouldn't a simpler solution be to take a step back and consider that, maybe, Newton's Laws are flawed? I am not trying to disprove dark matter, I certainly am no cosmologist, but it just seems odd that so much attention is given to dark matter, and very little is given to competing theories, such as MOND (Modified Newtonian Dynamics), that to me, at least, make more sense.

My basic point is, from a layman's perspective, dark matter just sounds like something physicists pulled out of thin air to explain something they don't understand. Your observations don't make sense? Well, throw in some dark matter and we're good!

Can someone explain to me why dark matter is the prevalent theory? Or perhaps why something like MOND is always ignored? As I said, I don't know what is right, but it just seems like a hack-job to me.

Re:Does Dark Matter exist?

[HarveyTheWonderBug]

It's not completely true that MOND does not get any attention, there are very regularly publications in refereed journals about it, to prove it, disprove it, or try to make it better. Here is the problem as I see it:

1. The current accepted theory of gravitation, general relativity, works extremely well: it's predictive power has so far never be successfully challenged. Many have tried, noone has succeeded.
2. MOND had some success in explaining various observational puzzles, but has also some problems with others, as the wikipedia entry you link indicates.
3. MOND is an ad-hoc theory, just like dark matter is an ad-hoc solution
4. It is very hard to change your theoretical framework, much easier to add some stuff to the universe.

This explains to me why, right now, the current accepted paradigm is dark matter. While it is not satisfying, it is enough to explain both the rotation curves of disk galaxies, and the formation and evolution of the large scale structure of the Universe. I don't think many astronomers are satisfied with this current situation, and some are trying to resolve the issue, either explaining dark matter or getting rid of it. The others find with dark matter a framework where they can go on in exploring other scientific questions, like the evolution of galaxies, where you need to explain how their (normal) matter was assembled together, but also how this matter (gas) is made into stars, etc...

Re:Does Dark Matter exist?

[NotZed]

# The current accepted theory of gravitation, general relativity, works extremely well: it's predictive power has so far never be successfully challenged. Many have tried, noone has succeeded.

You mean, apart from the fact that you need to create 90+ percent more matter in the universe than what is visible to prevent galaxies from flying apart?

i.e. without dark matter (and dark energy), gravity doesn't predict much.