Like Hollywood’s Ghostbusters, physicists Michael Turner and Bernard Sadoulet are pursuing quarry that’s insubstantial, elusive, and weird: it may not even exist. Their high-stakes hunt requires chutzpah--not to mention skill, imagination, money, and luck. Nevertheless, their pursuit is well supported by the physics community. That’s because the still- hypothetical particles they’re setting traps for may--just may--be the main ingredient of our universe. For now, these particles are the offspring of pure theory; even the equations tell us they’ll be almost impossible to observe. The trick is: How do you go about finding something that’s by nature almost unseeable? It’s like trying to put your finger on an idea.
Both scientists are seeking the shadowy stuff known as dark matter. It’s dark because it can’t be detected by any traditional means. It’s matter because it carries gravitational weight. Physicists believe in the existence of dark matter because of the overwhelming evidence that something unseen is exerting a powerful gravitational force. Locally, this force makes stars on the outer edges of galaxies orbit faster than they should; globally, it molds the very shape of the universe. This could be the ultimate Copernican revolution, says Sadoulet. Not only are we not at the center of the universe, but we may not even be made of the same stuff as the universe.
Sadoulet and Turner, it turns out, aren’t even looking for the same kind of stuff. Both the physicists’ candidates for dark matter would pass like ghosts through people, planets, and virtually any particle detector known to physics, but there the similarities end. Sadoulet’s neutralino is probably billions of times more massive than Turner’s axion. It has a rich social life, likely to have subtle but perhaps significant contact with lots of other particles. Axions interact with practically nothing: the best way to find one is to try to get it to change into something else.
Like the particles they seek, these two physicists represent starkly contrasting styles. The 43-year-old Turner is an earthy, exuberant soul whose cleated biking shoes can be heard clattering up and down the halls of the futuristic Fermi National Accelerator Laboratory outside hard- bitten Chicago. The natty, refined Sadoulet, 48, thrives in a more stately academic atmosphere, a traditional classroom building complete with pillars in chicly intellectual Berkeley. Turner’s speech is an all-American gush of neatly woven wisecracks. Sadoulet’s commentary is restrained, modulated by a gentle French accent.
Even the dark matter detectors they’re building to capture their particles of choice are like night and day. Sadoulet has a multimillion- dollar grant to build a supercold, superdelicate device out of a fist-size germanium crystal. Turner and his cohorts hunger for the brute force of the world’s most powerful magnet--which they are struggling to acquire secondhand at a fire-sale price from a government lab whose project went bust.
