Astronomers Make Important Dark Matter Discovery

saudadelinux writes "To quote a press release on NASA's site, astronomers using the Chandra X-ray Observatory have discovered 'how dark and normal matter have been forced apart in an extraordinarily energetic collision.' There will be a briefing at noon, August 21 ET, on this discovery, with streaming media provided by NASA, and some details of the research posted on Harvard's Chandra site just beforehand."

Comments

Re:Question.

[SupremoMan]

Not at all sir. http://en.wikipedia.org/wiki/Dark_matterThis should enlighten you a bit.

In cosmology, dark matter refers to matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation (light) to be detected directly, but whose presence may be inferred from gravitational effects on visible matter such as stars and galaxies.

It's a blanket term used for stuff in the universe we think is there but haven't seen because we can not detect it's presence.

**SPOILER**

[drxray]

They're referring to the Bullet Cluster. It's a merging system where a small cluster is passing through a large cluster leaving a shockwave that looks like a bullet's wake, hence the name.
Dark Matter is collionless, i.e. the DM from the smaller system hasn't been slowed down by the collion and just zooms through. The gas is slowed down. So, the DM and gas are no longer in the same place. We can see the gas in an X-ray telescope (Chandra) and detect the mass by the gravitational lensing effect on the background galaxies.
This is the first time that this has been shown, and it basically disproves the entire category of theories that DM is an illusional caused by us not understanding the action of gravity at long ranges (MOND).

Abstract from a conference talk about this. (PDF)

Re:Think that's bad?

[The Great Pretender]

There was a recent article in Discover that profiled a physist (Mordehai Milgrom) who had come up with modification on Newtons law to explain the planets orbits (forgive me, I'm a layman in this but it seems that dark matter started as a way to explain the weird plant orbits in extended galaxies - I encourage you all to correct me).

"Mordehai Milgrom never wanted to be a heretic. Twenty-five years ago, while poking around for a meaty research problem, he found one that changed the course of his career--and that might yet transform our most fundamental understanding of the universe. His ideas, long relegated to the fringes of physics, where all but cranks fear to tread, have finally become too intriguing for his mainstream colleagues to ignore. Milgrom's heresy? He denies the existence of dark matter, the shadowy and thoroughly hypothetical stuff generally held to make up 80 percent or more of all matter in the universe. Even though dark matter has eluded all attempts at detection, most cosmologists are convinced it must be out there."

So potentially there may not be any dark matter and the vast money being spent on it's pursuit is being wasted. For the record I don't believe in string theory either. I have to say that I would love to subscribe to the simplicity of Milgroms ideas, but it's just a gut check that fitting the theory to the data is better than creating a fudge factor - which dark matter ultimately seems to be.