Inside a former gold mine a mile below the surface, inside a titanium tank filled with a rare liquid gas, scientists have begun investigating what has happened so far.: Dark matter.
Scientists are fairly certain that invisible things make up most of the mass of the universe and say that without it we would not be here – but they do not know what it is. The race to solve this huge mystery has brought a team to the depths under Lead, South Dakota.
The question is fundamental for scientists, said 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 one mile of dirt and rocks, a huge tank, a second tank and the purest titanium in the world will block almost all the cosmic rays and particles that surround us – and through it – all of us every day. But dark matter particles, scientists think, can avoid all those obstacles. They hope that someone will fly into the liquid xenon vat of the inner tank and break into a xenon nucleus like two balls in a pool game, revealing its existence in a flash of light seen by a device called the “time projection chamber”.
Scientists announced Thursday that the five-year, $ 60 million search finally began two months ago after a delay caused by the COVID-19 epidemic. Device found so far … nothing. At least there is no dark matter.
That’s right, they say. The tools seem to be working to filter out most background radiation they expected to block. “To investigate this very rare type of interaction, the first task is to first get rid of all the common sources of radiation that will overwhelm the experiment,” said Carter Hall, a physicist at the University of Maryland.
And if all their calculations and theories are correct, they assume that they will see a few transient signs of dark matter in a year. A team of 250 scientists estimates they will get 20 times more data in the next few years.
By the time the test is over, the chances of finding dark matter with this device are “probably less than 50% but more than 10%,” said Hugh Lipincott, a physicist and test spokesman, at a news conference Thursday.
While it’s a far cry from a sure thing, “you need a little encouragement,” says Lawrence Berkeley’s Lesco. “Don’t go into rare search physics without hoping to find something.”
The two Halking Depression-era lifters run an elevator that brings scientists to the LUX-ZEPLIN test at the Sanford Underground Research Facility. A 10-minute landing ends in a tunnel where the cooler-to-touch walls are lined with mesh. But the old, massive mine soon leads to a high-tech lab where dirt and pollution are the enemy. Helmets are exchanged for new cleaners and a double layer of Baby Blue boots goes over the steel toe protection boots.
The focus of the test is a giant tank called the Cryostat, Chief Engineer Jeff Cheruinka said during a December 2019 visit before the device was turned off and full. He described it as “like a thermos” made of “probably the purest titanium in the world” designed to keep liquid xenon cool and minimize background radiation.
Xenon, in particular, explains Aaron Manalois, coordinator of experimental physics, because it allows researchers to see if a collision is with one of its electrons or with its nucleus. If something hits the nucleus, it’s more likely to be a dark matter that everyone is looking for, he said.
These scientists tried a similar, small experiment here years ago. After coming up empty, they thought they had to go bigger. Another large-scale test is underway in Italy, run by a rival team, but no results have been announced yet.
Scientists are trying to understand why the universe is not what it seems.
Part of the mystery is Dark Matter, which contains most of the mass of the universe. Astronomers know that it is there because when they measure them and other regular matter in the galaxy, they find that there is almost not enough gravity to hold these clusters together. If there was nothing else, the galaxies would “fly away quickly,” Manales said.
“Understanding our observations of the history of the evolutionary universe without dark matter is essentially impossible,” Manals said.
“We wouldn’t be here without dark matter,” said Santa Barbara, a physicist at the University of California, Lipinkot.
So while there is little doubt about the existence of dark matter, there is much doubt about what it is. The leading theory is that it involves things called WIMPs – weakly interacting with massive particles.
If so, LUX-ZEPlin may be able to detect them. We want to find out “where the wimps may be hiding,” Lippincott said.