Photons traveling through a cloud of atoms can emerge so early that they appear to have spent a negative amount of time ...

A photon enters a cloud of atoms and emerges on the other side. When physicists calculate how long the atoms remained excited because of that transmitted photon, the answer falls below zero.

Add Yahoo as a preferred source to see more of our stories on Google. Scientists measured a negative weak value for the time photons left atoms excited, while later studies revealed how quantum ...