Labs trying to shed light on dark-matter mystery

LOS ANGELES — In deep underground laboratories around the globe, a high-tech race is on to spot dark matter, the invisible cosmic glue that's believed to keep galaxies from spinning apart.

Whoever discovers the nature of dark matter would solve one of modern science's greatest mysteries and be a shoo-in for the Nobel Prize. Yet it's more than just a brainy exercise. Deciphering dark matter — along with a better understanding of another mysterious force called dark energy — could help reveal the fate of the universe.

Previous hunts for the hypothetical matter have turned up nothing, but that has not deterred some two dozen research teams from plumbing the darkness of idled mines and tunnel shafts for a fleeting glimpse.

Dark-matter detecting machines today are more powerful than previous generations, but even the best has failed so far to catch a whiff of the stuff. Many teams are now building bigger detectors or toying with novel technologies to aid in the hunt.

"We're in the golden age of dark-matter search," said Sean Carroll, a California Institute of Technology theoretical physicist who has no role in the experiments. "It's looking good for some breakthroughs to happen."

Scientists admittedly are still in the dark about dark matter. The prevailing theory is that it's made up of tiny, exotic particles left over from the Big Bang some 13.7 billion years ago. Dark matter, thought to make up a quarter of the universe's mass, gets its name because it doesn't give off light or heat. Astronomers know it exists because of its gravitational tug-of-war with stars and galaxies.

Knowing that dark matter exists is a far cry from knowing what it is. Most experiments are searching for theoretical particles called WIMPS — or weakly interacting massive particles — the leading dark-matter candidate.

The underground custom-built machines are all waiting for the rare moment when a WIMP hits the atomic nucleus and causes an elastic recoil. Experiments have to run below ground to prevent cosmic rays from interfering with the results.

Dark-matter researcher Neil Spooner of Sheffield University in England sums it up this way: "You have a needle in a haystack and you're trying to remove the hay. You need better technology to pull out the event you're looking for and reject the rubbish."