In this video, Dr. Demetrios Matsakis, Chief Scientist for USNO’s Time Services at the US Naval Observatory (located in Washington DC), explains in detail how the US Naval Observatory Master Clock works, including how the time gets communicated to your phone.

All forms of digital communication – military operations, banking systems, the internet, cell phone networks – depend on the Observatory’s precise time.

Over 100 atomic clocks are used to compute the time. There are three types of timekeeping used: Cesium clocks, laser-based clocks and atomic fountains (which use lasers as well). These technologies are combined together to provide a time that is accurate to 16 decimal points. In other words, together, they will not lose or gain 1 second in 300 million years.

“It is the most accurate measuring device ever created by mankind,” says Matsakis.

Time is disseminated from the Naval Observatory to GPS satellites to cell towers to your phone. The time is also broadcast over the internet or via a phone line (202-762-1401).