Here's a cool video about a man named Dr. Judah Levine. He works at the National Institute of Standards and Technology and helps a team keep track of time with atomic clocks. If atomic clocks failed, the entire world would essentially come to a halt because so many systems are locked into the atomic clock infrastructure. Thankfully, the likelihood of that scenario is slim since there are over 400 atomic clock stations spread across the world, all for the purpose of keeping time but also as redundant backup systems for each other.