The universe has a speed limit, and it's the speed of light. Nothing can travel faster than light — not even our best spacecraft — according to the laws of physics. So, what is the speed of light?

The speed of light is a fundamental constant, approximately 299,792,458 meters per second. It's the same for all observers and hasn't changed measurably over billions of years. Nothing can travel ...

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 ...

James is a published author with multiple pop-history and science books to his name. He specializes in history, space, strange science, and anything out of the ordinary.View full profile James is a ...

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 ...

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, ...