Tuesday, August 22, 2006

I'm sorry I called you an epicycle

It appears that I owe dark matter an apology. I may be a physicist only by osmosis, but I'm a science historian by (undergraduate) training, so I've studied the fall of a lot of good-seeming ideas. I figured dark matter was just this year's epicycle; it seemed so inelegant to invent a new substance just because the numbers didn't work out. Even though I know that a lot of cosmic phenomena were discovered with number-crunching, I was much more prepared to believe that gravity operates differently under certain conditions. (After all, it's different at the very small level -- why not at the very large level?)

But now there's this front-page article from the Post:
After studying data from a long-ago collision of two giant clusters of galaxies, researchers now say they are certain dark matter does exist and plays a central role in creating and defining gravity throughout the universe.

While the scientists are still not sure exactly what dark matter is, since they have yet to identify it in a laboratory, they said that the workings of the universe cannot be explained without it.
One of the researchers is quoted as saying that "we now have direct proof" of dark matter, which of course I have to object to on a philosophical level. And unfortunately, whether it's a matter of reporting quality or experimental complexity, I can't quite tell what this all-important data was or why this constituted a risky test. One University of Maryland scientist is quoted as saying that "proof" of dark matter particles would require "grabbing them in the laboratory, not just inferring that their effects can be the only possible explanation for an observation before the alternatives have actually been checked," and I think that's more than fair. At least until I find a better explanation of the data, there's still room for skepticism.

But personally, I feel less skeptical now that there's some observation involved. Not that there wasn't observation before, but what we were observing was gaps and inconsistencies, and we made a very good guess about what caused them. Now, it appears, there's evidence. Mind you, said evidence is rather confusingly presented ("The super-hot gases have qualities that typically would have become the seat of any new gravitational fields, cosmologists say, but instead they went with the stars") but it's a far cry from "well, the orbits would work out a lot better if we put in some extra circles and moved the center point." It's starting to look like I won't get to see the rules of gravity rewritten in my lifetime.

On the flip side, though, this presents a great opportunity to market our new book on the subject!

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