Wednesday , May 31 2023

‘I’m waiting for a dream’: search for dark matter under 1 km of Australia | Australian news


Dark matter is now flowing through.

These mysterious, invisible things make up more than 80% of the universe, a network of particles that pass freely through matter. To observe this, it is necessary to get rid of all interventions.

You have to close the universe to learn the things of the universe.

The Center for Dark Matter Particle Physics Excellence of the Australian Research Council is doing this in an unused part of a gold mine under the town of Stawell, Victoria, one kilometer underground.

Workers in a dark substance laboratory
Stawell’s gold mine, a group of Australian scientists are studying dark matter. Photo: Center for Perfection for Dark Matter Particle Physics

There, a cave becomes a laboratory for dark matter hunters and is nearing completion by the end of the year.

Alan Duffy, an astronomer at Swinburne University and director of the Institute of Space Technology and Industry, describes dark matter as a “fantasy.”

By saying, “Dark matter is a cloud that surrounds us … it passes through us, through solid walls, through the Earth,” he likens it to the wind that is only visible through its effects.

“The gigantic structures that surround the universe, the cosmic whites, and the galaxies we see and live in, stretch along filaments of dark matter like dew in the morning in a spider’s web in the courtyard.

“As you read this, you will experience several hundred million particles per second, possibly colliding with your atoms in a matter of days.”

The vast majority of particles pass through you, looking at only a few failed atoms.

That’s why you need a radio silence to find them.

Phillip Urquijo, the center’s chief researcher, says that although more than 80 percent of the universe’s mass is made up of dark matter, it only interacts with other matter – gravity.

And to observe this means to prevent the interference of other particles. Radiation from the sun and from the radioactive decay of ordinary matter and the launch of the first atomic bombs from radioactive particles contaminated with metals (later on) is a mixed picture.

Inside the lab for dark substance hunters
The lab for dark matter hunters is scheduled to be completed in the new year. Photo: Center for Perfection for Dark Matter Particle Physics

In the laboratory, there are 1000 meters of rock between the researchers and the surface, rock slabs to block cosmic rays. But wait – there is more.

“We put the experience as deep as we could in Australia, into one of the first working gold mines,” says Urquijo. “We can block the sun’s cosmic rays, but the rock and any material we use in our experiments may contain naturally occurring radioactivity.”

The cave is covered with a net and some kind of concrete is sprinkled on it. Then there’s the search for pure metal.

Radioactive dust spills from atomic bombs have infected metals since World War II, meaning that many people trying to detect dark matter have to get a source of metal before the bombs can explode. For example, from ancient shipwrecks.

“When producing steel, it consists of new steel, iron ore and recycled iron. The steel produced during and after World War II ended up with a component of radioactivity left over from weapons testing,” Urquijo said. “One option is to rescue ships, ancient Roman ships and sunken submarines that sank on the ocean floor long ago and were not penetrated by cosmic rays.”

That’s what many dark substance hunters have to do – but Urquijo says they can get a cleaner version of steel, and Duffy says they’ve put in some preservatives.

Duffy, the project’s lead researcher, says they have set up a “veto system” unlike other projects that have saved lead ingots from 2000-year-old sunken Roman castles.

The team created the purest crystals possible, sodium iodide crystals with lower pollution levels than previously produced.

The pure crystals, which will glow when a particle is struck, are encased in copper tubes, inside a steel container, with a special liquid that will glow when struck by a particle (this is called a scintillator liquid).

“Now we’re looking for this light in two places,” he says.

“If a crystal glows, we look at the surrounding liquid, and if the liquid glows, we know that it cannot be a dark substance, because the probability of dark matter hitting atoms twice is infinitely small.”

Inside the lab for dark substance hunters
The Stawell project is part of Sodium Iodine, an Active Background Rejection Experience. Photo: Center for Perfection for Dark Matter Particle Physics

Think of the millions of particles flowing through you right now, and how they are rarely pierced by an atom. A different particle may fall into the water, and then it becomes a pure, compact crystal. Two flashes. The dark matter particle is so unlikely to touch anything that there will be only a flash.

Astronomers have long theorized about dark matter.

For decades, hunters of dark matter have looked at the behavior of galaxies, how light bends, and the evidence for their existence using space telescopes. As this evidence grew, so did the perception that dark matter was everywhere around us and could be studied on Earth.

The Stawell project is part of the Active Reversal Experiment (Saber) of Sodium Iodine, which seeks to detect dark matter particles directly, rather than indirectly through their effects. It is a partner of the southern hemisphere of a similar structure in Italy.

Duffy says that as we learn more about dark matter, technology will break down and spread – learning how the atom breaks down has given us nuclear medicine (and undesirable weapons that have so polluted everything on the planet).

Dark matter also plays an insignificant role in ensuring the existence of galaxies — and extensions — in general. There must be something that provides the force of gravity that allows galaxies to form and still stop them from flying apart.

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“You can create a universe on a supercomputer – that’s what I do,” he says. “If you don’t put dark matter there, it doesn’t have enough gravity to form galaxies. We owe our existence to dark matter.

“The big question we want to answer about our universe was raised in the earliest moments of the universe and is very important for us to understand fundamental physics.”

Dark matter hunters continue to hunt in a gold mine with the Hubble Space Telescope, a large hadron collision, and a lab under a Victorian steppe.

It is expected to be commissioned in the new year. Then Duffy says “expect a dream.”

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