On one hand, the speed of light is just a number: 299,792,458 meters per second. And on the other, it’s one of the most important constants that appears in nature and defines the relationship of ...

In 1676, by studying the motion of Jupiter's moon Io, Danish astronomer Ole Rømer calculated that light travels at a finite speed. Two years later, building on data gathered by Rømer, Dutch ...

Light is faster than anything else in the known universe, though its speed can change depending on what it's passing through. When you purchase through links on our site, we may earn an affiliate ...

In a Universe governed by General Relativity, filled with matter-and-energy, a static solution is not possible. That Universe must either expand or contract, with measurements revealing very quickly ...

Light is the fastest-moving thing in the universe. So what would happen if the speed of light were much, much slower? In a vacuum, the speed of light is about 186,000 miles per second (300,000 ...

Michael Lam does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their ...

Chris Impey receives funding from the National Science Foundation and the Hearst Foundation. Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, ...