Have we spotted hints of gravitons? zf L/Getty Images Physicists have been searching for gravitons, the hypothetical particles thought to carry gravity, for decades. These have never been detected in space, but graviton-like particles have now been seen in a semiconductor. Using these to understand gravitons’ behaviour could help unite the general theory of relativity and quantum mechanics, which have long been at odds. “This is a needle in a haystack [finding]. And the paper that started this whole thing is from way back in 1993,” says Loren Pfeiffer at Princeton University. He wrote that paper with several colleagues including Aron Pinczuk, who passed away in 2022 before they could find hints of the elusive particles. Pinczuk’s students and collaborators, including Pfeiffer, have now completed the experiment the two began discussing 30 years ago. They focused on electrons within a flat piece of the semiconductor gallium arsenide, which they placed in a powerful refrigerator and exposed to a strong magnetic field. Under these conditions, quantum effects make the electrons behave strangely – they strongly interact …