In the never-ending search to accurately describe the universe, new generations of scientists are adapting decades-old technology to make new discoveries.
Sometimes those techniques don鈥檛 find what they鈥檙e looking for, but still result in more knowledge and new approaches, as researchers in Ohio State University鈥檚 astronomy and physics department have found in their search for dark matter using radar.
Like many scientific discoveries, radar was finetuned as a tool for war, becoming an important part of World War II after is discovery decades earlier.
Now it's used for everything from navigation to weather forecasting.
And Ohio State University researchers have found yet another use. In a recent , three researchers working under physics and astronomy professor outlined a new technique to search for dark matter.
Their initial approach used data generated by radar technology set up to detect meteorites entering the atmosphere at observatories in Japan and Antarctica.
When something like a meteor enters the atmosphere, observatories can use radar to find the particles they leave behind. The larger ones create shooting stars, while the smaller ones will leave a trace that can still be detected.
鈥淚f you look up at the sky, you don't see anything. But a big cloud of electrons will reflect radio waves. So, if we send radar signals from the ground, it will go up there and it'll bounce off of those electrons just like it's like a little piece of metal in the sky," Beacom said.
The team theorized that if dark matter particles are large enough, and interact with regular matter enough, they might show up in the data.
鈥淒ark matter makes up about 85% of the matter in the universe," said , who was a PhD student who worked on the paper with Beacom, along with Pawan Dhakal and Steven Prohira. 鈥淏ut we don't know what it is, to be rather blunt about it," Cappiello said.
Beacom said dark matter is just the name of the concept describing matter that hasn鈥檛 yet been accounted for in the universe.
鈥淲e don't know if it's really massive particles, and there's not that many of them, or little, low mass particles, and there's a lot of them. We know how much total mass there is, but we don鈥檛 know the identity of the particles,鈥� Beacom said.
But we know there鈥檚 some massive amount of matter out there that hasn鈥檛 been accounted for yet, because of the way galaxies and stars are moving through space.
鈥淎nd all of this evidence is pointing to the idea that most of the mass in galaxies, in fact, most of the mass in the universe, is something that we cannot see. It's not just the stars and gas and things that we're able to see with a telescope,鈥� Cappiello said.
Beacom said to understand where our understanding of dark matter lies today, think about the way humanity first started to understand germ theory.
鈥淔or a long time, people knew that something made people sick. But they didn't know what it was. And they had all kinds of crazy theories, and you know, about vapors and cold weather and hexes," Beacom said.
Over time, people came to understand the idea that 鈥済erms鈥� were being passed from one person to another, though they couldn鈥檛 see the organisms to study them, he said.
鈥淭hey started to have a name or a concept, but they didn't actually know what it was. And that's sort of like where we are with dark matter. We know it鈥檚 a thing,鈥� Beacom said, we just haven't been able to observe it, yet.
This experiment looked for large, highly interacting particles.
鈥淲e did not discover dark matter," Cappiello said.
But, the research still added to the knowledge of what dark matter doesn鈥檛 do.
鈥淲e are able to say, if dark matter existed anywhere in this parameter space, we would have seen it, but we did not," he said.
And, Beacom said the approach to using radar can be adapted to search for particles of other masses and levels of interaction.
鈥淭his whole approach could be greatly improved. These radar data that we used are intended to find these little, teeny tiny meteors,鈥� Beacom said.
Cappiello remains fascinated by the unknown and is continuing his studies on dark matter as a postdoctoral fellow at Queen鈥檚 University in Ontario.
鈥淚f you discover dark matter, you win the Nobel Prize,鈥� Cappiello said.
Scott Palo and John Marino with the University of Colorado also assisted with their work at the observatory in Antarctica.
