It’s absolutely incredible that the most accurate atomic clocks lose only about 1 second over 138 million years. But how exactly do they work? Bill Hammack, The Engineer Guy, explains the science behind these time-keeping marvels in his latest video. Using cesium atoms to create a feedback loop, a block of quartz is electronically “nudged” to keep its oscillations consistent. And this amazing accuracy is a critical part of GPS technology. According to Bill, being off by even a milisecond could mean an error of about 300 kilometers.