Light has always been the stage on which quantum mechanics performs its strangest tricks, and the double-slit experiment is still the star of that show. A new, ultra-clean version of this classic test ...

The constancy of the speed of light is a pillar of modern physics, but questions persist about its absolute universality. Advanced theories, seeking to unify general relativity and quantum mechanics, ...

Add Yahoo as a preferred source to see more of our stories on Google. When you buy through links on our articles, Future and its syndication partners may earn a commission. An artistic celebration of ...

Scientists pushed photons across the universe to test the speed of light—and found Einstein’s cosmic speed limit still holds ...