April 21st, 2008
OK, so astronomers “detect” dark matter in action all the time, and there is very clear evidence the stuff is real and not just some misunderstanding of how gravity works. You can refresh yourself on the history of dark matter and the evidence here. So what’s new?
A serious claim from the DAMA Project of the direct detection of dark matter particles, AKA WIMPs (Weakly Interacting Massive Particles). Here’s Dennis Overbye’s NYT article that ran yesterday for the pop science take. Unlike some of my recent rants about some awful science reporting, Overbye at the NYT is one of the best in the business.
On the surface, I find the data convincing (8.2 sigma is very convincing). Something is colliding into their experiment, and there is a very significant seasonal change in the measurements. This is critical since the motion of the Earth through space as it moves around the sun, relative to any dark matter, should produce such a modulation. And we’re talking about an experiment a mile down in the Earth where surface conditions shouldn’t matter. The worry, of course, is that there’s something in their system yet unaccounted for with an annual variation. The importance of this discovery will make everyone scrutinize the results very careful and hold the experiment to the highest standards. It’s the sort of thing you win the Nobel Prize for.
You can read some more detailed and skeptical posts by the Bad Astronomer and Cosmic Variance. The latter, in particular, has a guest blog entry by Juan Collar, a competing expert in the field, who gives you the perspective of how another scientist regards such a claim. He believes the data, too, but is cautious about over interpretation. There’s some good stuff there, too, about how scientists look at things. Check it out.