Bad news: Time travel is impossible

You might think time travel has always belonged in the world of fantasy, but 10 years ago some scientists began to believe time travel might actually be possible when superluminal — or faster-than-light — propagation of some specific medium were discovered. It was later found to be a visual effect, but the idea that a single photon could exceed the speed of light lingered, and with it, the possibility of time travel.

But in a study published in the peer-reviewed scientific journal Physical Review Letters, Shengwang Du and his team measured the ultimate speed of a single photon and showed that it cannot move faster than the speed of light.