In a former gold mine a mile underground, inside a titanium tank filled with a rare liquified gas, scientists have begun the search for what so far has been unfindable: dark matter. Scientists are pretty sure the invisible stuff makes up most of the universe's mass and say we wouldn't be here without it—but they don't know what it is. The race to solve this enormous mystery has brought one team to the depths under Lead, SD, reports the AP. Scientists announced Thursday that the five-year, $60 million search finally got underway two months ago after a delay caused by the COVID-19 pandemic.
The question for scientists is basic, says Kevin Lesko, a physicist at Lawrence Berkeley National Laboratory: "What is this great place I live in? Right now, 95% of it is a mystery." The idea is that a mile of dirt and rock, a giant tank, a second tank, and the purest titanium in the world will block nearly all the cosmic rays and particles that zip around—and through—all of us every day. But dark matter particles, scientists think, can avoid all those obstacles. They hope one will fly into the vat of liquid xenon in the inner tank and smash into a xenon nucleus like two balls in a game of pool, revealing its existence in a flash of light seen by a device called "the time projection chamber."
Astronomers know dark matter exists because when they measure the stars and other regular matter in galaxies, they find that there's not nearly enough gravity to hold these clusters together. If nothing else was out there, galaxies would be "quickly flying apart," says experiment physics coordinator Aaron Manalaysay. So far the device has found ... nothing (at least no dark matter), but the scientists don't seem to be discouraged. lf their calculations and theories are right, they figure they'll see only a couple of fleeting signs of dark matter a year.
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There are 250 scientists taking part in the LUX-ZEPLIN experiment in the Sanford Underground Research Facility, and by the time the experiment finishes, the chance of finding dark matter with this device is "probably less than 50% but more than 10%," said Hugh Lippincott, a physicist and spokesman for the experiment, in a Thursday presser. These scientists tried a similar, smaller experiment here years ago. After coming up empty, they figured they had to go much bigger. Another large-scale experiment is underway in Italy run by a rival team, but no results have been announced so far. (More dark matter stories.)
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