Many US folks just changed their clocks for daylight saving time, and here in California we’re voting on a proposition that might lead to changes in California’s time standards, so quite a number of people have time on their minds. Meanwhile, on a national level, Trump intends to defund one of the mechanisms we use to to synchronize time across the country.
The National Institute for Standards and Technology operates timecode radio stations. As explained in Wikipedia:
Both WWV and WWVH announce the Coordinated Universal Time each minute, and make other recorded announcements of general interest on an hourly schedule, including the GPS satellite constellation status and severe oceanic weather warnings.
And if you follow that path far enough, you might learn that those radio stations were critical to our early understanding of satellite behavior:
WWV’s 20 MHz signal was used for a unique purpose in 1958: to track the disintegration of Russian satellite Sputnik I after the craft’s onboard electronics failed. Dr. John D. Kraus, a professor at Ohio State University, knew that a meteor entering the upper atmosphere leaves in its wake a small amount of ionized air. This air reflects a stray radio signal back to Earth, strengthening the signal at the surface for a few seconds. This effect is known as meteor scatter. Dr. Kraus figured that what was left of Sputnik would exhibit the same effect, but on a larger scale. His prediction was correct; WWV’s signal was noticeably strengthened for durations lasting over a minute. In addition, the strengthening came from a direction and at a time of day that agreed with predictions of the paths of Sputnik’s last orbits. Using this information, Dr. Kraus was able to draw up a complete timeline of Sputnik’s disintegration. In particular, he observed that satellites do not fall as one unit; instead, the spacecraft broke up into its component parts as it moved closer to Earth.
Basically, the WWV radio signal was part of a very large, hemisphere-wide radar tracking the disintegration of Sputnik in the atmosphere.