The quest for dark matter is one of the ultimate pursuits of modern physics. Scientists dug deep – literally – to try to find this elusive material. But now some are thinking of a change of direction.
Dark matter is theorized to represent around 85% of the matter in the universe, with the remaining 15% represented by visible matter.
Cosmologists are pretty sure it exists because of how they have observed stars in other galaxies orbiting galactic centers. The orbits of stars far from the center only make sense if there is more matter in the galaxies than can be seen. Much more.
Dark matter, however, eluded direct detection for decades.
Dark matter research experiments are already under construction or underway. Such tests must be deep underground to reduce the “noise” of other particles, such as muons, passing through the device. One such laboratory is the “Genius Lair”, located in a gold mine beneath the Victorian town of Stawell.
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But what if, instead of looking under our feet in search of dark matter, we were to look up?
Physicists are now proposing a new way to search for dark matter by sending an atomic clock to the sun to act as a “quantum sensor”.
The distribution of dark matter in the solar system is dictated by gravity. The sun makes up about 99.8-99.9% of the total mass of our solar system. Therefore, in theory, we should be more likely to find dark matter around our central star, where the sun’s gravitational pull makes dark matter the densest.
Researchers from Japan’s Kavli Institute for the Physics and Mathematics of the Universe (IPMU), as well as the University of California (UC), Irvine and the University of Delaware – both in the United States – United – published an article in natural astronomy describing their new proposed dark matter detection method.
The team says it was partly inspired by NASA’s Deep Space Atomic Clock and the organization’s Parker Solar Probe.
Parker demonstrated that NASA’s new solar shield allows spacecraft to get closer than ever to our sun. The Deep Space Atomic Clock represents the next generation of high-sensitivity atomic clocks used to navigate in space.
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It’s not just any old dark matter the team hopes to find. Their method is specifically designed to search for dark matter particles with extremely small masses.
Light dark matter is predicted to induce oscillations in certain universal constants, such as the mass of electrons and the fine structure constant which measures the strength of the electromagnetic force. Such fluctuations in these fundamental constants of nature would in turn affect the transition energies in atoms.
Atomic clocks work by measuring the frequency of photons emitted when atoms transition between different states. Any oscillation caused by dark matter would be detected as an emitted photon of a different frequency.
“The more dark matter around the experiment, the greater these oscillations, so local dark matter density matters a lot when analyzing the signal,” says co-author Dr Joshua Eby of Kavli. IPMU.
There are currently no plans to implement the concept. However, researchers believe that future space missions using atomic clocks could double as dark matter detection experiments.
“Long-range space missions, including possible future missions to Mars, will require exceptional timing, much like atomic clocks would in space,” says Eby. “A possible future mission, with very similar shielding and trajectory to the Parker Solar Probe, but carrying an atomic clock device, might be sufficient to complete the search.”
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