Matter and antimatter should have destroyed each other in the moments after the Big Bang. That they didn’t is yet another enduring mystery of physics.
Physicists are facing a matter/antimatter conundrum: they can’t find a good reason to explain why the universe actually exists.
It sounds like a classic episode of classic Star Trek when someone inexplicably shuts down the warp engines, some imminent threat looms, and — right on cue — Scotty says: “Captain, I canna’ change the laws of physics.”
On its face, it’s a flight of fancy, a philosophical question akin to how many angels fit on the head of a pin. But it’s actually the logical conclusion from one of the most advanced scientific studies ever conducted and recently published in the journal Nature.
The experiment looked hard at antiprotons in an attempt to better understand what might have happened just after the Big Bang — the cataclysmic event that created the universe billions of years ago.
The Big Bang was caused by particles and antiparticles crashing into each other in a dance of mutually-assured destruction. We know it occurred because the universe literally glows with the remnants of that collision in what is known as the Cosmic Microwave Background.
But although we know matter was created after the Big Bang, we don’t know how that matter was created. The theory has always been that, for some unknown reason, that The Big Bang was asymmetrical, with far more particles of one kind, and those particles — mostly matter, enigmatic dark matter, with a dollop of antimatter — were expelled outward on a journey of billions of years to create the universe.
So far, the experimental results chronicled in Nature suggest that the subatomic particles were expelled by the Big Bang in equal concentrations, but that answer leads to an inherent contradiction. If that’s the case, the Big Bang collision of matter and antimatter would have canceled out both sides of the equation, creating a huge sea of energy, and nothing that could expand and coalesce into galaxies and solar systems and planets and us.
The research suggesting this baffling result was designed to measure a property of antiprotons that is known as the magnetic moment.
“There’s got to be some difference between matter and antimatter in order to explain what happened to antimatter,” says Makoto Fujiwara, a leading researcher at TRIUMF, Canada’s national laboratory for particle physics who runs antimatter experiments at CERN in Geneva. Scientists thought that the answer might be the magnetic moment, suggesting that maybe matter might enjoy a slightly different vector when subjected to a magnetic force than antimatter. If so, that might explain why matter is common in the universe.
It’s been a popular hypothesis, but one that is almost impossible to test because antimatter is as elusive as a leprechaun. Except when you’re an incredibly creative team of researchers.
To test the hypothesis, CERN researchers lead by Christian Smorra used a proton synchrotron to slam a beam of protons into metal, thereby create a cascade of elementary particles. Using several brilliant scientific tricks, they were able to collect, cool, and isolate antiprotons to measure their magnetic moment.
Previous experiments had been conducted to answer this question, but the sample sizes were infinitesimal even by the standards of quantum mechanics, and the results simply weren’t precise enough to show any differences between the two opposing particles. Smorra and his team were able to improve on those measurements by several hundred times.
The end result is that we have now defined the magnetic moment of protons and antiprotons to a significant number of decimal points, and they are still identical, though opposite.
So we’re back to square one, with no clear understanding about why matter survived the Big Bang in far greater concentrations than antimatter.
For the profoundly religious, such secular experiments are a complete waste of time when faith provides all the answers. But for physicists, delving deeply into the origins of the universe, one of the most essential ways to be fully human, and fully spiritual is to be inquisitive, to always ask why.
“Science is not only compatible with spirituality; it is a profound source of spirituality,” wrote astronomer Carl Sagan 20 years ago. “When we recognize our place in an immensity of light‐years and in the passage of ages, when we grasp the intricacy, beauty, and subtlety of life, then that soaring feeling, that sense of elation and humility combined, is surely spiritual.”