Imma Perfetto
Cosmos science journalist
How do you look for something that doesn’t absorb, reflect, or emit light? A team of researchers has developed a new way to use atomic clocks aboard GPS satellites and a network of ultra-stable lasers to search for dark matter.
“Despite many theories and experiments scientists are yet to find dark matter, which we think of as the ‘glue’ of the galaxy holding everything together,” says Ashlee Caddell, a PhD student at the University of Queensland in Australia, who co-led the study published in Physical Review Letters.
When we look out to the universe, the visible stuff we see and interact with is normal matter. But to make sense of observations of gravity within and around stars, galaxies, and galaxy clusters, something else must be there too. And lots of it.
This is dark matter and its thought to make up 85% of the matter in the universe. The problem is that it is almost impossible to detect, because it only very weakly interacts with ordinary matter through gravity.
The new study attempted to detect a type of dark matter model known as “ultralight dark matter”.
“Dark matter in this case acts like a wave, because its mass is very, very low,” says Caddel.
They did this by analysing data from a network of ultra-stable lasers connected by fibre optic cables on Earth, as well as from 2 atomic clocks aboard GPS satellites.
“We use the separated clocks to try to measure changes in the wave, which would look like clocks displaying different times or ticking at different rates, and this effect gets stronger if the clocks are further apart,” says Caddell.
“By comparing precision measurements across vast distances, we identified the subtle effects of oscillating dark matter fields that would otherwise cancel themselves out in conventional setups.
“Excitingly, we were able to search for signals from dark matter models that interact universally with all atoms, something that has eluded traditional experiments.”
UQ physicist and co-author Dr Benjamin Roberts says the study brings researchers closer to understanding one of the universe’s most elusive and fundamental components.
“Scientists will now be able to investigate a broader range of dark matter scenarios and perhaps answer some fundamental questions about the fabric of the universe,” says Roberts.
