The Universe Should Be Empty. A Single Trapped Antiparticle Might Finally Reveal Why It Isn’t.

The conventional picture of Big Bang cosmology holds that 13.8 billion years ago, all mass and energy was packed into a singularity, a state that predated even atoms, protons, and quarks. Then, a lot happened in a very short time, including the rapid inflation of the universe and the creation of the fundamental building blocks of matter, which eventually coalesced into, well, everything.Except that shouldn’t have happened at all, according to the Standard Model, otherwise known as Lambda-Cold Dark Matter, or ΛCDM model. During that immense Big Bang (which, of course, didn’t produce any “bang” at all), matter and antimatter created mere fractions of a second after the cosmic event should have annihilated one another in equal measure, leaving behind only a rapidly expanding void filled with radiation—no stars, no planets, no us. But, as evidenced by your eyeballs scanning these very words, that very much didn’t happen, and instead we live in a universe dominated by matter.So…what gives?Our existence is the result of what scientists call the “matter-antimatter asymmetry”: for every billion matter-antimatter pairs created at the universe’s birth, one particle of matter somehow survived. That suggests that the Standard Model, our best theory of how the universe works, is incomplete. Now, a new study led by Northwestern University scientists details a promising technique that could help solve this cosmological conundrum.In an article in the journal Physical Review Letters, the researchers explain how they essentially “trapped” an anti-electron, otherwise known as a positron, for months, creating what they call a “one-positron quantum cyclotron.” Antimatter annihilates on contact with ordinary matter, as it did in the first moments after the Big Bang, so holding even a single particle requires a nearly perfect trap.“If we want to study antimatter, we must handle it carefully,” Northwestern physicist Gerald Gabrielse, senior author of the study, said in a press statement. “To be clear, it’s not dangerous. We don’t have enough antimatter to make an explosion.”To capture the positron, researchers relied on radioactive decay from sodium-22, a rare isotope of sodium. Once the positrons emerged, the researchers guided a single one into the trap’s near-perfect vacuum, then cooled it to just 300 millikelvins above absolute zero. The whole process took less than 12 hours.This process lowered the particle to its quantum ground state, and the scientists could then deliver energy via finely tuned microwaves to study the particle’s quantum transitions. The goal was to eventually gain a complete understanding of the particle’s magnetic properties and compare the results to the team’s previous work with a one-electron quantum cyclotron.“Current theories suggest that there will be no difference in the two measurements,” Gabrielse said in a press statement. “If it turns out they are not equal, that would be the biggest discovery in physics in the last century.”Paolo Crivelli, a physicist at Swiss Federal Institute of Technology (ETH) Zurich, who’s unaffiliated with the study, writes for Physics that this research is an “experimental breakthrough,” but it’s not enough on its own to provide high-precision measurements of a positron’s “g factor,” which describes the relationship between the particle’s magnetic moment and its angular momentum.“Achieving such a measurement will require detailed spectroscopy and exquisite control of systematic effects,” Crivelli cautions.Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.