Time travel might still be in the realms of science fiction, but that doesn't mean you can't change the past. Just don't build your hopes up too much.

As New Scientist explains, when it comes to photons, we can decide after the event how they traveled through space—like arriving in San Francisco from L.A., only to then decide if you drove or flew. Confused? Watch the video to make sense of it all. [New Scientist]