A new map generated by a group of physicists and geologists from around the country could be used to better understand the workings of the universe and track global nuclear activity.
Antineutrinos — the tiniest known elementary particles — are produced by nuclear reactions from the sun, from man-made nuclear reactors across the globe or from radioactive processes occurring deep beneath the surface of the Earth, said Bill McDonough, a University of Maryland geology professor and co-author of the study. Research on worldwide antineutrino distribution was published in September in the Scientific Reports journal.
Two large detectors, one stationed in Japan and the other in Italy, were used to measure concentrations of antineutrinos around the earth, McDonough said. The darker spots on the map indicate higher concentrations of antineutrinos and therefore higher levels of radioactivity, he said.
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There are about 10 billion neutrinos per square centimeter per second raining down on us, passing through people and the Earth’s surface, McDonough said. Thus far, they have been a “very large mystery” to scientists. Only now are researchers getting a chance to study these particles and measure their properties.
“The Earth has lots of processes that need energy, such as plate tectonics, and [scientists] have been trying to understand the fuel that powers the Earth’s engine,” McDonough said. “They try to understand the energy that comes from the Earth and try to pin down what fundamental building blocks are used to make the Earth.”
Glenn Jocher, Ultralytics founder and co-author of the study, said neutrinos and their antimatter counterpart, antineutrinos, are essentially like puzzle pieces of the universe. Scientists are still trying to figure out how these pieces fit into the puzzle of the universe, he said, but human study of them has its limitations.
“You can dig a tunnel into the Earth, for example, but it gets hotter and hotter the deeper you go. And the deepest people have ever gotten is probably about 10 or 15 kilometers. So if you want a better picture of what’s going on inside the Earth, you have to use some secondary means,” Jocher said. “This map — probably the most detailed of its kind — tells us a little more about the inner workings of the Earth.”
This antineutrino map could serve another purpose beyond building a greater understanding of fundamental matter, McDonough said.
Nuclear reactors that burn uranium produce antineutrinos, McDonough said, so some of the “hot spots” account for man-made nuclear activity. This means that the radioactivity associated with these processes can be tracked by this kind of mapping.
“We can use these new techniques to monitor the activities of nuclear reactors around the world,” he said.
Monitoring radioactivity is a hot topic these days, Jocher said.
Jordan Goodman, a university physics professor not involved with the study, said this facet of the map could be extremely useful.
“There is no way to shield the presence of neutrinos or antineutrinos,” Goodman said. “So we could tell if there was any nuclear reactor activity going on in secret.”
McDonough said compared the map to having an antineutrino flashlight.
“We have data to show us who is burning nuclear fuel,” McDonough said. “So in theory, we can tell if someone has turned their nuclear reactor off … or monitor nuclear activity if we found a signal where we didn’t expect one.”
