Dark matter

While you and I are obsessing over our Christmas gift list or, on a grander scale, hating Joe Lieberman for his antics in the U.S. Senate, some of our fellow humans are pondering the nature and future of the universe.

News comes this week from the Soudan Mine in the chilly iron mining country of northern Minnesota. After two years of reading sensors located in an old mine 2,000 feet underground, chilled almost to absolute zero (0.01° K.), scientists have observed two tiny blips of heat, which they suspect are the result of the sensors being hit by a couple of WIMPS. No, the WIMPS aren't the scientists; they are Weakly Interacting Massive Particles -- a form of "dark matter." The odds are about 75-80 percent that the detectors have detected WIMPS, rather than simply picking up some form of background radiation. Because of the small possibility of background "noise," however, no claim is being made at this time of a conclusive "dark matter" detection. But scientists are optimistic.

Dark matter particles are dark because -- although heavy -- they do not emit light, they have no electrical charge, and they virtually never interact with other particles. They just hang around space being heavy. Apparently, however, they do interact with the germanium/silicon detectors that the scientists have installed under the Mesabi Range, thus permitting the reported detection.

Dark matter, until now, has been a theoretical construct, hypothesized to explain why the universe, once created in the Big Bang, hasn't flown apart like scraps of an exploded firecracker. The universe is expanding, yes, but in a controlled expansion. The mutual gravitational attraction among all particles is the accepted explanation for the limited speed of expansion, but there's nowhere near enough visible matter to provide the graviational pull that would explain the observed data. Therefore, scientists have for some time suggested the existence of "dark matter" -- matter massive enough to provide the required gravitational tug to keep the stars from flying apart much faster than they do, but matter so "dark" that we can't detect it by our senses and instruments.

Until now. Maybe.

If dark matter exists, there's a lot of it around. Scientists calculate that 25 percent of the mass of the universe is dark matter, as compared with only 4 percent being found in atoms (including visible matter composed of atoms). (The rest of the universe's mass -- an incredible 70 percent or so -- is believed to be "dark energy," mass/energy that the predominant theory suggests is inherent in the nature of space itself).

Other scientific teams are working to confirm the Minnesota identification of dark matter, including an American team working in the Italian Alps, and the CERN team operating the LHC (Large Hadron Collider) near Geneva (the collider I've discussed in earlier posts).

Pretty cool stuff. Pondering these matters should calm us and diminish the usual irritation caused by the elevated mass and energy of frenzied Christmas shoppers at the local Wal-Mart.