It’s been over 340 years since Danish physicist Ole Rømer observed that the speed of light was finite. And, to this day, photons still manage to surprise us. Last year, scientists revealed a new fundamental property of light. This year, a team of physicists from by the Trinity College Dublin and the CRANN Institute have just discovered a new form of light that refuses to behave normally, and undermines what physicists know about angular momentum.
“Angular momentum measures how much something is rotating,” one of the study’s researchers, Kyle Ballantine, told Trinity News. “For a beam of light, although traveling in a straight line it can also be rotating around its own axis.” Up until this finding, physicists thought the angular momentum of all forms of light was a multiple of Planck’s constant. Apparently, that’s not so.
To uncover this information, the researchers began by searching for new behaviors of light by shining beams through crystals to create “screw-like structures.” They used the theory of quantum mechanics to analyze these beam structures and realized that the angular momentum of the photon would be a half-integer, not a multiple of Planck’s constant.
This discovery might not sound like much, but researchers suggest that it will influence our knowledge about the very essence of light. “Our discovery will have real impacts for the study of light waves in areas such as secure optical communications,” Professor John Donegan said.
Finding a new form of light is undoubtedly exciting. However, much of the physics community’s real joy comes from validating 30-year-old theoretical physics predictions. In the 1980s, physicists speculated ways in which quantum mechanics would open doors for strange new discoveries, such as particles with fractions of their expected quantum numbers. This research provides the first validation of those predictions. “This discovery is a breakthrough for the world of physics and science alike,” said CRANN Director, Stefano Santo.