In his famous thought experiment, a 16-year-old Albert Einstein imagined what it would be like to travel as fast as a beam of light. If he rode alongside, traveling at light speed, he wrote, “I should observe such a beam of light as an electromagnetic field at rest.” For the observer, in this case Einstein, time itself would slow down. This, among other thoughts, would lead Einstein to theorize about how time is relative. Time and speed have an inverse relationship — should you find yourself approaching the speed of light, you’ll note that time slows down.