Scientists think they might have finally seen signs of dark matter. Not in outer space, but on Earth
&imwidth=600&imheight=450&format=webp&quality=medium "Scientists think they might have finally seen signs of dark matter. Not in outer space, but on Earth")
Was dark matter finally detected on Earth? An experiment might have picked it up . Photograph: (NASA)
Scientists got a glimmer of hope in their search for dark matter at the Sanford Underground Research Facility in South Dakota. A single interaction between subatomic particles inside a tank remains unexplained, and researchers think dark matter could have been present.
Scientists have recorded a single interaction between subatomic particles deep beneath what used to be a gold mine in South Dakota, which remains unexplained by known background signals from normal matter. This anomaly was recorded in the data from the world’s most sensitive dark matter detector and is the most compelling sign yet of the elusive material that supposedly makes up 85 per cent of the mass in the universe.
The dark matter experiment a mile deep
The findings were recorded at the Sanford Underground Research Facility, or SURF, where the LUX-ZEPLIN (LZ) Dark Matter Experiment has been going on since 2012. The detector sits a mile below the ground and is managed by the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).
Flashes of light sparkle in a shielded tank filled with 10 tons of ultra-pure liquid xenon when weakly interacting massive particles, or WIMPs, collide with xenon atoms. The detector looks for dark matter, and 250 scientists and engineers from 39 institutions analyse the data.
During one such review of data collected by the detector over 220 days, between March 2023 and April 2024, researchers were looking for faint signals from the simplest kinds of WIMP interactions. Later, they started poking for more energetic interactions. This is when they came across an event that exhibited a spectrum of nuclear recoil energy which they could not explain in the context of known background signals involving normal matter.
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“The LZ collaboration has gone to extraordinary lengths to try to find a mundane explanation for what we saw in the data. At the end of the day, for now, it’s just one event," Associate Professor of Physics Cecilia Levy, a researcher from UAlbany and involved in the LZ project, said.
If the particle, or the WIMP that generated the anomalous event, was indeed dark matter, it would have been more than 200 times the mass of a proton. "We’re very intrigued to see this event in the data, in the region where we expect dark matter to show up, and the competing backgrounds are very low,” Rick Gaitskell, a professor at Brown University and the spokesperson for LUX-ZEPLIN, said in a statement.
The team says they would need more than one anomalous event to be sure if the mysterious dark matter was involved.
Dark matter and dark energy - The elusive forces that remain unseen
Dark matter has remained a theory for decades. Scientists still don't know what it is or if it even exists. Swiss astrophysicist Fritz Zwicky first proposed the existence of dark matter in 1933. He was studying the Coma Cluster of galaxies and noted that the total mass of the galaxies should be 400 times greater than what could be accounted for by visible starlight.
American astronomer Vera Rubin found in the 1970s that this same problem was present in other galaxies as well. Astrophysicists concluded that invisible matter is present in the universe, but they could never uncover any proof.
Scientists believe ordinary matter only makes up 5 per cent of the universe's mass-energy content, with dark matter being 27 per cent and dark energy the other 68 per cent. With the launch of the Nancy Grace Roman Telescope, the investigation into dark matter and dark energy is expected to take a few leaps.
