Catching sight of dark matter

"I would say we have millions of dark matter particles passing through our bodies every day, continuously," says Elisabetta Barberio, Professor of Physics at the University of Melbourne and the Director of the ARC Centre of Excellence for Dark Matter Particle Physics.

“The dark matter particle gets its name because it doesn’t emit light. So, if you have a telescope, you cannot see it. But it does not only not emit light in the visible spectrum, it doesn’t emit any electromagnetic radiation, so radio waves, infrared, ultraviolet.

“No matter which kind of astronomical instrument you try to look at the sky, you cannot see it,” Professor Barberio says.

She explains that we know that galaxies have been formed at a certain time in the history of the universe, and they’ve been formed where there were pockets of this dark matter. So, we know that dark matter is there.

“To catch dark matter that is all around us in the galaxy, we need to go deep underground because we don’t want all these cosmic rays that reach us every day from the sun, the stars and the galaxy to spoil the signal of dark matter.

“We found the perfect site in Stawell, near the Grampians because there’s a gold mine that is one of the deepest mines in Australia. They offered to host us one kilometre underground.”

The experiment has been called Stawell Underground Physics Lab or SUPL, the first of its kind in the world.

“We have another experiment under the Gran Sasso in Italy that showed a signal that could be interpreted as a dark matter particle signal. This is huge and quite important. However, no other experiment has been able to replicate the signal,” Professor Barberio says.

“Dark matter is the majority of the material of the universe, so at the end of the day, we know only five per cent of the universe. It’s just exploring the most unknown.”

Episode recorded: July 22, 2020.

Interviewer: Dr Andi Horvath.

Producer, audio engineer, editor: Chris Hatzis.

Co-production: Silvi Vann-Wall and Dr Andi Horvath.

Banner image: This image from the Hubble Space Telescope indicates that a huge ring of dark matter likely exists surrounding the centre of CL0024+17 that has no normal matter counterpart. NASA, ESA, M. J. Jee and H. Ford et al. (Johns Hopkins University)