Scientists observe 'negative time' in quantum experiments

FILE - A student walks in front of the University of Toronto, St. George campus, in Toronto, Sept. 26, 2023. FILE - People take a break from playing sports on the grounds of the University of Toronto, Sept. 9, 2020.

Scientists have long known that light can sometimes appear to exit a material before entering it — an effect dismissed as an illusion caused by how waves are distorted by matter.