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Friday, November 21, 2014

Dark-Matter Detectives: the Clocks Aboard GPS Satellites

As reported by GPSWorld“Networks of correlated atomic clocks, some of them already in existence, such as the Global Positioning System, can be used as a powerful tool to search for topological defect dark matter, thus providing another important fundamental physics application for the ever-improving accuracy of atomic clocks,” write physicists Andrei Derevianko and Maxim Pospelov in the current issue of Nature Physics journal.

Derevianko teaches at the University of Nevada, Reno, and Pospelov at the University of Victoria and the Perimeter Institute for Theoretical Physics in Canada. Derevianko and Geoff Blewitt, director of the Nevada Geodetic Laboratory at the University of Nevada, Reno are testing this dark-matter detection theory by analyzing clock data from atomic clocks aboard GPS satellites, searching for instances where initially synchronized clocks might have become desynchronized. They expect time discrepancies between spatially separated clocks to exhibit a distinct signature, one that may reveal the nature of spatial dark matter.
The Geodetic Lab developed and maintains the largest GPS data processing center in the world, according to a University of Nevada statement, able to process information from about 12,000 stations around the globe continuously, 24/7.
“We know the dark matter must be there,” explains Blewitt, “because it is seen to bend light around galaxies, but we have no evidence as to what it might be made of. If the dark matter were not there, the normal matter that we know about would not be sufficient to bend the light as much as it does. That’s just one of the ways scientists know there is a massive amount of dark matter somewhere out there in the galaxy. One possibility is that the dark matter in this gas might not be made out of particles like normal matter, but of macroscopic imperfections in the fabric of space-time.”

“Despite solid observational evidence for the existence of dark matter, its nature remains a mystery,” said Derevianko. “Some research programs in particle physics assume that dark matter is composed of heavy-particle-like matter. This assumption may not hold true, and significant interest exists for alternatives.
“Modern physics and cosmology fail dramatically in that they can only explain 5 percent of mass and energy in the universe in the form of ordinary matter, but the rest is a mystery.”
Scientific evidence reportedly shows that dark energy constitutes about 68 percent of the mystery mass and energy. The remaining 27 percent may be dark matter, though it has never been detected or measured.
“Our research pursues the idea that dark matter may be organized as a large gas-like collection of topological defects, or energy cracks,” Derevianko added. “We propose to detect the defects, the dark matter, as they sweep through us with a network of sensitive atomic clocks. The idea is, where the clocks go out of synchronization, we would know that dark matter, the topological defect, has passed by. In fact, we envision using the GPS constellation as the largest human-built dark-matter detector.”