Shedding light on dark matters


Bucktown's Map Room bar was unusually crowded for a Monday evening, with people crammed into every table and leaning against the map-covered walls. The attractions weren't only organic pizza and international beers but also a discussion with astronomy & astrophysics professor Michael Turner, focusing on dark energy and dark matter. The event, part of the Cafe Scientifique series, drew both U of C and unaffiliated listeners, who turned their ears to hear Turner's baritone voice—even with a microphone he was sometimes faint amid other patrons' conversations across the bar.

We're in "the golden age of cosmology," Turner said, on the verge of answering "questions that Einstein and Newton couldn't answer." Cosmologists are close to sorting the puzzle of dark matter, which makes up 25 percent of the universe and holds it all together—"universal glue," he called it. "We think it's just particles," he said. Dark matter's particles are lighter than neutrinos and are called neutralinos. While he'd like to produce a neutralino at Fermilab, the particle accelerator there probably isn't strong enough, so later this summer he and other scientists will travel to Switzerland to use the machine at CERN.

Next up is figuring out dark energy, which makes up 71 percent of the universe (the other 4 percent is atoms) and has been battling the dark-matter glue by driving the universe's expansion. ("Who came up with the term dark energy? That's dumb," he joked before raising his hand and laughing: "That's me." Turner coined it in 1998.) Unlike dark matter—and everything else—dark energy doesn't seem to be made up of particles. It's more like "a sheet that's so elastic it can't be pulled apart." While Turner discussed dark energy, the microphone blew out, leaving some listeners in the dark. Then the mic came back. "OK," he said, "we're talking about the fate of the universe."

He looked to the far future: billions of years from now the universe might "stop expanding and fall back on itself," or, according to string theory, it could "collapse and then start over again." After audience questions about black holes, government science funding, and the big bang, the event was over. But many people waited for a chance to talk with Turner one-on-one, hoping to get more answers about the cosmos.


Photos: An SRO crowd listens to Michael Turner at the Map Room; when the microphone went out, Turner stood on a table so the group could hear.

June 18, 2008