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 ...

There's an ultimate speed limit in the Universe: the speed of light in a vacuum, c. If you don't have any mass — whether you're a light wave (a photon), a gluon, or even a gravitational wave — that's ...