how fast does light travel?
Credit: Iscatel | Shutterstock. The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light. In miles per hour, light speed is, well, a lot: about 670,616,629 mph. If you could travel at the speed of light, you could go around the Earth 7.5 times in one second. Early scientists, unable to perceive lightâs motion, thought it must travel instantaneously.