Physicists at CERN have observed the light emitted from antimatter for the first time, bringing us one step closer to unraveling one of the longest-standing problems in physics today – why is it that regular matter is so much more abundant than antimatter in the Universe?
Standard models suggest that for every particle of matter created in the Big Bang, an antiparticle was also created. Antiparticles are identical to their regular-particle counterparts in every sense except one – they possess an opposite charge. But because of this property, if an antiparticle comes in contact with a regular particle, the two particles annihilate. And so scientists are puzzled by this apparent asymmetry in the Universe today. At some point very early on in the history of our Universe, something must have happened to tip the scale in favor of regular matter, leaving antimatter virtually undetectable.
Because of this overabundance of regular matter, observing naturally occurring antimatter is difficult, since it will quickly come into contact with regular matter and annihilate. Instead, scientists at CERN devised a way to create antimatter in the lab, producing up to 25,000 antihydrogen atoms in less than 15 minutes, and trapping roughly 14 of them. Shining a high intensity laser beam on the antihydrogen particles, scientists observed the light emitted as a positron (a positively charged electron) within the antihydrogen jumped from one energy level to the next, stimulated by the laser light. The signature of the light emitted – or its spectrum – matched exactly the spectrum emitted by a regular hydrogen particle, confirming our standard model of particle physics and even Einstein’s theory of special relativity.
Nevertheless, future experiments with greater precision will be needed in order to confirm whether the emission and absorption of light by antimatter mirrors that of regular matter precisely, or whether our standard model requires tweaking. Until then, we remain only one step closer to understanding the elusive nature of antimatter.
Acknowledgements: Many thanks to Andy Greenspon, a Ph.D. candidate in Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences, for his helpful knowledge on the subject.
Managing Correspondent: Tarraneh Eftekhari
Scientific Paper: Observation of the 1S–2S transition in trapped antihydrogen – Nature
Media Coverage: Physicists have observed the light spectrum of antimatter for first time – Science Alert