A single antimatter particle has been held in place for months in a striking physics experiment that could open new avenues for testing the fundamental laws of the universe.
Researchers at Northwestern University successfully trapped one positron—the antimatter counterpart of an electron—without allowing it to collide with ordinary matter, an event that would cause the two to annihilate. The achievement, detailed in new research, required extraordinary precision: even a minor error could have destroyed the experiment.
The team confined the positron inside an ultra-cold apparatus, using powerful magnetic and electric fields to suspend it in a vacuum. Their findings were published in Physical Review Letters.
“We actually coaxed this very fast positron to sit there and behave for months at a time,” lead researcher Gerald Gabrielse told the technology and science outlet Interesting Engineering.
To prevent the particle from touching the walls of its container, the scientists created a device known as a “one-positron quantum cyclotron.” Near-zero temperatures, along with precisely controlled electromagnetic fields, kept the positron floating in empty space rather than coming into contact with any physical surface.
The first-of-its-kind experiment also placed the particle in its lowest possible energy state. That allowed researchers to manipulate and monitor it with exceptional precision over several months, opening the door to detailed comparisons between antimatter and the ordinary matter it mirrors.
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Working under Gabrielse’s direction, the Northwestern team captured the positron as it emerged from radioactive material. They then cooled it to just 0.3 degrees above absolute zero—about negative 459.67 degrees Fahrenheit.
The biggest challenge, Gabrielse said, was slowing the rapidly moving particle enough to capture it in the first place.
The breakthrough could help scientists investigate one of cosmology’s most enduring puzzles: why the universe is composed almost entirely of ordinary matter. Under the standard account of the Big Bang, matter and antimatter should have been produced in roughly equal quantities, allowing them to annihilate one another billions of years ago.
While the Big Bang model remains the leading explanation for the universe’s early history, some researchers have explored alternatives, including the possibility that the cosmos emerged from a “bounce” within a black hole, as The Post previously reported.
So far, the positron has shown no measurable behavior that differs from that of a regular electron. However, the new apparatus could make future comparisons roughly 30 times more precise, according to the American Physical Society.
“Current theories suggest that there will be no difference in the two measurements,” Gabrielse said.
“If it turns out they are not equal, that would be the biggest discovery in physics in the last century,” he added.
