For three years, scientists have been
looking for dark matter—which
though invisible, makes up more than four-fifths of the universe's
matter—nearly a mile underground in a former gold mine in Lead, South Dakota.
But on Thursday they announced at a conference in England that they didn't find what they
were searching for, despite sensitive equipment that exceeded technological
goals in a project that cost $10 million to build.
We're sort of proud that it worked so
well and also disappointed that we didn't see anything," said University
of California, Berkeley physicist Daniel McKinsey, one of two scientific
spokesmen for the mostly government-funded project.
The mine project, called Large
Underground Xenon experiment or LUX, was one of three places looking for dark
matter. Another is on the International Space Station and a third is an effort
to create dark matter at the Large Hadron Collider, run by the European
consortium that found the Higgs Boson particle.
At the South Dakota site, more than
4,800 feet of earth helped screen out background radiation. Scientists used a
large vat of liquid xenon that they hoped would produce a flash of light when
weakly interacting massive particles, or WIMPS, bounced off the
super-cooled liquid.
Not finding WIMPS may drive physicists
to think about new candidates for dark matter, even though WIMPS are still the
most viable option, said Neal Weiner, director of the Center for Cosmology and
Particle Physics at New York University, who was not part of the research.
Scientists are already starting to
revamp the South Dakota mine site for a $50 million larger, higher-tech version
of LUX, called LZ, that will be 70 times more sensitive and should start
operations in 2020, said Brown University's Richard Gaitskell, another
scientific spokesman for LUX.
Even that won't be easy. Dark matter is
everywhere. Hundreds of millions of dark
matter particles pass through Earth every second, Gaitskell said.
But the problem is they are "just crazy weak" and they zip through
Earth as if it barely exists, he said.
Gaitskell has spent 28 years hunting
these particles.
"Over 80 percent of our matter is
in this dark matter form. You and I are the flotsam and jetsam; dark matter is
the sea," Gaitskell said. "That's why one doesn't give up. We've got
to figure out what this dark matter component is."
When pressed, Gaitskell acknowledged
the possibility, however slight and unlikely, that scientists are looking for
something that isn't there.
"It's certainly there. We know
dark matter exists" because of the way it helps form galaxies and makes
light bend around galaxy clusters, McKinsey said.
Weiner said, "It's hard to know
when we will find dark matter because we don't know precisely what it is. Of
course, that's what makes the search for it such a big deal."
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