MINNEAPOLIS — A long-elusive key to understanding the universe may have been discovered a half-mile below the Iron Range.
Scientists announced Thursday they believe they have detected evidence of dark matter in data collected at an underground physics lab in Soudan, Minn.
Dark matter most likely accounts for most of the universe’s total matter, but its existence has never been proven. If it ever is, it could unpack mysteries about the behavior of stars and galaxies.
According to the Department of Energy’s Fermilab, which is conducting the search for dark matter at the Soudan lab, “judging by the way galaxies rotate, scientists have known for 70 years that the matter we can see does not provide enough gravitational pull to hold the galaxies together. There must exist some form of matter that does not emit or reflect light.”
In the announcement, the lab said the Cryogenic Dark Matter Search experiment has “detected two events that have characteristics consistent with the particles that physicists believe make up dark matter.”
But, it cautioned, there is “a chance” the events could be the signatures of background particles that merely mimic the signals of dark matter.
According to Fermilab, dark matter “may have provided the gravitational scaffolding that allowed normal matter to coalesce into the galaxies we see today. In particular, scientists think our own galaxy is embedded within an enormous cloud of dark matter. As our solar system rotates around the galaxy, it moves through this cloud.”
Particle physics theories suggest dark matter is composed of Weakly Interacting Massive Particles. WIMPs would rarely interact with normal matter, but may occasionally bounce off, or scatter from, an atomic nucleus like billiard balls, leaving a small amount of energy that is detectable under the right conditions.
The Soudan lab has been searching for WIMPs since 2003. It uses 30 detectors cooled to nearly absolute zero in an attempt to detect WIMP scatters.
“This is a very intriguing result — we really don’t know if this is a background or a signal,” said Lauren Hsu, a researcher at Fermilab who announced the experiment’s results Thursday. “As an experimenter you always wish you had more data.”
Researchers and physicists at the University of Minnesota, one of nine universities conducting the research, planned to hold a seminar on the experiment this afternoon.
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