What is time? A deceptively simple question, yet it is the key to understanding relativity. Is time universal? In other words, is there an audible tick-tock throughout the galaxy? A master clock, so to speak, forging ahead like Mozart’s metronome? The answer, my friends, is no. But understanding time is essential to understanding relativity. Ten meters per second, 100 miles per hour. But a mathematical description of velocity is moot unless we can define time.
Now, close your eyes.
