GPS satellites to aid in hunt for elusive dark matter
Dark matter is hypothesized to account for the large amounts of "missing" invisible matter in the universe where visible objects such as stars, gas, and dust are insufficient to explain the total gravitational effects observed. Despite repeated and verifiable observational evidence supporting this hypothesis, the existence of dark matter remains unproven. However, recent research has suggested that the hunt for this elusive substance may be aided by detecting any changes in the synchronization between the individual atomic clocks on-board satellites in the orbiting GPS network and receivers on the ground as waves of dark matter pass between them and the surface of the Earth.
Of the dark energy and dark matter that's believed to make up around 95 percent of all the missing energy and matter in the universe, some 68 percent is dark energy. The other 27 percent is commonly recognized to be dark matter, despite the fact that it is neither visible nor detectable through direct detection and measurement methods.
"Despite solid observational evidence for the existence of dark matter, its nature remains a mystery," said Professor Andrei Derevianko of the University of Nevada, Reno. "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."
GPS satellites carry several super-precise atomic clocks on board, the time measurements of which are used in combination with transmissions of their position to allow a ground-based receiver to measure the relative time delay between satellites to determine the receiver’s position in relation to the satellites and, therefore, the position of the receiver on the surface of the Earth.
Derevianko, and his associate Maxim Pospelov, of the University of Victoria, Canada, have posited the notion that these satellites could be used to search for dark matter because of the easy access to time signals from the large number of rubidium and cesium clocks contained in the network of GPS satellites encircling the Earth. As such, the researchers assert, these clocks should provide a sufficient array of easily-accessible comparisons to detect any shift in the synchronization of transmitted time signals affected by any passing dark matter field.
As a result, in analyzing clock data transmitted from the 31 GPS satellites currently in orbit, the researchers hope to use the network as a potent, cross-correlated instrument to hunt for the topological defects intrinsic to dark matter. It is hoped that this will be evidenced by initially synchronized clocks becoming de-synchronized.
"Our research pursues the idea that dark matter may be organized as a large gas-like collection of topological defects, or energy cracks," said Professor Derevianko. "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."
Using the Geodetic Lab also located at the University of Nevada, Professor Derevianko is analyzing the collected GPS data in collaboration with director of the lab, Professor Geoff Blewitt. The Geodetic Lab is the biggest center of GPS data processing in the world, and is capable of continuously processing information from around 12,000 stations located all around the Earth.
"We know the dark matter must be there, for example, because it is seen to bend light around galaxies, but we have no evidence as to what it might be made of," said Professor Blewitt. "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. The Earth sweeps through this gas as it orbits the galaxy ... As the dark matter blows by, it would occasionally cause clocks of the GPS system to go out of sync ... If the dark matter causes the clocks to go out of sync by more than a billionth of a second we should easily be able to detect such events."
The research was published in the journal Nature Physics.
Source: University of Nevada