The first satellites in space were not there to look at the stars; they were up to look back down on earth — specifically into the land of the enemy, and, as a side benefit, for location tracking. When the Soviet Sputnik launched, American scientists quickly learned they could track the satellite’s movement by “listening” for the doppler signature of the signals. Three satellites were enough to triangulate a location; more gave better precision. By the late 1970s the U.S. used no fewer than six in guiding nuclear submarines, which spent months at a time under the waters. The guidance system was called NAVSTAR GPS.

On this day, May 2, in 2000, Bill Clinton announced the unscrambling of some of the GPS satellite signals, allowing civilians for the first time to use them in tracking their own locations – a useful tool first for commercial mining and oil extraction businesses, which eventually spread to the public at large.

Not limited to just navigation, a cornucopia of new uses has grown around GPS. Atmospheric researchers use the displacement of the signals to study wind and air conditions at the upper reaches of the planet, while geologists place GPS receivers at fault lines to detect and record earthquakes. Everything from power grids to financial networks are now hooked in to the GPS system.