Slashdot Mirror
Galaxy Sans Dark Matter
ChromaticDragon writes "Astronomers have crunched some numbers on a galaxy to discover that its rotation can be fully explained by the gravity of the observable matter — in effect, this galaxy seems to lack dark matter. This shouldn't come as a total surprise given that one of the stronger observations of Dark Matter was the
Bullet Cluster where supposedly a good deal of Dark Matter and good old fashion regular matter had separated."
I'm not sure if it is the story the submitter was trying to link to, but this article seems to cover the subject.
I thought that was supposed to be a joke... would have been much more effective if it immediately shutdown your computer when you clicked it though...
Black Matter [Click Here]
Black Screen...
All the Dark Matter is there, it just was told to move to the back of the galaxy.
Learning HOW to think is more important than learning WHAT to think.
No (or negligible) dark matter in our galaxy, eh?
When we're looking farther away, we're looking back in time, too. So perhaps the observations could be explained by "constants" of physics (notably the gravitational constant) varying with the age of the universe, rather than by the gravitational pull of some otherwise-unobservable dark matter.
Let's see if "dark matter" is "more dense" the farther away we look... B-)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
This is another nail in the "dark matter can be solved with a modified theory of gravity" coffin. If we can find a galaxy composed of stars whose observed motion is entirely explained by the mass of those stars and known theories of gravity (Newton, Einstein) that's a serious blow to theories like MOND.
I'm certainly no expert on the subject, but as far as I am aware Dark matter is matter that fills the equasion when the visible matter doesn't compute...
If a galaxy without dark matter computes, and a galaxy with visible matter with the addition of dark matter computes...
Whats the difference? wouldnt a galaxy made up of entirely dark matter be equal to a galaxy of entirely visible matter?
If you have 3 fish, and two of them are transparent zebrafish, and one is a normal opaque one... they are still 3 fish... as far as im concerened, this doesnt really prove anything other than matter effects other matter wether its visible or not which we already know... however it may disprove that dark matter is neccisary to create a galaxy? (if anyone was actually pondering that?)
Sure. But most of the galaxies we have observed seem to be made up of a mixture of dark matter and visible matter, given their gravitational characteristics. Finding a galaxy with no matter isn't any sort of physical impossibility, but it's surprising because it's not the norm. If most galaxies contain dark matter, then something unusual must have happened to this one for it not to contain dark matter, and that's interesting; beyond that, the fact that such a thing even could happen may give us insights into the nature of dark matter.
Broken link? I don't think so..
It says 404.. Not Found.. Pretty much in line with TFS...
'Let's see if "dark matter" is "more dense"' I dunno, usually blond matter is more dense...
Excuse me, but please get off my Pennisetum Clandestinum, eh!
Umm, no.
There are some good reasons to believe it isn't normal matter that isn't making light. For starters one would still expect it to absorb light and thus be observable. Additionally our models of galaxy formation would suggest it should have a certain distribution which doesn't conform with what is necessery to explain the rotation behavior. In fact it may even need to be relatively free from interactions to be as spread out as needed. Most relevantly the observations that suggest that dark matter doesn't collide with itself or normal gas when galaxies collide suggests it isn't normal matter.
Of course your general sentiment is right. There are reasons to believe dark matter isn't made up of neutrinos but it isn't any more mysterious than they are. It is probably just some weakly interacting particle much like those we have already discovered.
If you liked this thought maybe you would find my blog nice too:
Every time I read a story like this, I can't help but think of the following quote from Hitchhiker's:
I sometimes wonder if perhaps there is a God, and he is changing the rules on us. Like maybe until the time of Newton, it was the case that mass didn't vary with velocity, and that you could continually apply a force and accelerate to infinite speeds. And then Newton came around, discovered those rules, and God supplanted them with relativity. And then Einstein came along, and God said "hmm, let's add dark matter and make things more interesting."
Sort of like when I was a kid playing battleship, I would track my opponent's guesses on my lower board. And if they guessed where one of my ships was, I would discretely move the ship to somewhere they didn't guess yet and announce a miss. Except with physical laws.
I don't think this is a reasonable thing to actually believe, but it would be amusing. If I were God I would totally do that.
Only that dark matter isn't necessarily a new particle or has to be a product of fantasy. That's among the debated things. All it seems to be is some sort of particle with a mass that doesn't reflect light or emitting much else that can be detected, making it dark. So some theories have said it could be neutrinos, or maybe neutralinos, that are actually predicted to exist by modern theories.
Beware: In C++, your friends can see your privates!
It's just a way for the editors to abrogate their responsibilities while blaming the users when crappy submissions get posted.
I thought I could contribute a bit to the discussion by giving some background on why the theory of dark matter came about.
Vera Rubin's work on galaxy rotation rates is still pretty compelling evidence for dark matter... OR, at least, it shows us that all galaxies do not behave they way we think they should, to be more accurate. People much smarter than my own self have decided that "dark matter" or some sort of mass/force/something that does not emit light or radio waves, etc. (which is why we never noticed it before) must be responsible.
When we look at a solar system like ours, we see that the farther a planet is from the sun, the slower it travels. Not only does it have a much longer way to go, but it doesn't - and according to what we understand, shouldn't - travel as fast.
Vera Rubins decided to check a whole galaxy. What she found did not hold with our understanding. The solar systems, stars and other observable matter near the outside were traveling faster than expected.
Vera Rubin's work, combined with the discovery that the univers appears to be expanding at an accelerating rate, rather than slowing down, kind of kicked off the whole dark matter/dark energy thing.
Well, my days of not taking you seriously are certainly coming to a middle. -Firefly
If the universe was full of life what would it look like? Just roll the idea around for a while. Look at what current SF writers are thinking about, that we may soon be starting on our own primitive Dyson Sphereshttp://en.wikipedia.org/wiki/Dyson_sphere. That we may eventually use all the energy from our sun and give of no visible radiation. It might seems impossible now but imagine we are going to work on the problem for a million years. If the universe was full of intelligence, I think it would look just like what we see now.
The cool thing is, if I were God, I could create an alternate universe in which I invented the finglonger.
Out of modpoints but really liked a post? 1BDkF6TtmmeZ3yqXbz9yhdYVqRYnwFoXDj