In our pockets, we have a tool so powerful that it dwarfs the power of the computer that went to the Moon. Its development required the unprecedented collaboration of all branches of the military and many different countries during increasingly hostile times, and its seeds were planted in the early 1800's. It is a technology that truly did take 200 years to develop, yet most of us take it for granted. I am talking about GPS: a service which allows us to locate ourselves on a map anywhere in the world. To create a truly global positioning system, the U.S. had to collaborate with Russia in the midst of the Cold War as well as create entirely new technologies based solely on science-fiction or convert old technologies for an entirely different purpose. Of all the services we talk for granted in the modern world, GPS is the most modern. Yet we still know so little about who created it, how it works, and what was necessary for it to be created.
GPS is a complicated system: to understand how it works, we first must understand how satellites work, and to understand how satellites work, we must understand the Space Race. In October of 1957, the Russians launched Sputnik, the first ever man-made satellite, which transmitted a radio signal which could be heard on even the cheapest at-home radios of the era. We rushed to launch our own satellite, and thus began the space race, which only ended in 1969, when Neil Armstrong set foot on the Moon. The Space Race lead to many new technologies(including LED's), but the most important one was the satellite. As the Space Race drew to a close, many military men realized that satellites could be paired with another recent technology to create a positioning system.
Atomic clocks are the second crucial part of GPS. In 1949, scientists first channeled the explosive power of the atom towards timekeeping. Their goal was to define the second on a basis not based on the length of the solar year. In 1967, scientists finally used the Cesium atoms to create an atomic clock used to redefine the second as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Caesium-133 atom". After the Space Race, a man named Roger Easton realized that by putting these clocks in space, he could determine his position on the Earth with an astonishing accuracy.
GPS Satellites are all geostationary, meaning that they orbit the Earth at the same rate as the Earth spins on its axis. This means that the Satellites are always above the same spot on the Earth, making them a constant frame of reference. GPS Satellites constantly send out radio waves in a pattern of different frequencies. When a receiver locks on to the signal, it begins repeating it and then measures the delay from the repeated signal to the next instance of the original GPS signal. The delay amount is the time taken for the radio waves to reach the receiver. By multiplying this by the speed of light, you can find the distance from the satellite. By doing this for two more satellites, you can find your exact position on the Earth. More satellites can be used to more accurately measure the time delay using atomic clocks, making the system even more accurate.
The GPS system is revolutionary in many ways. It was used in Operation Desert Storm for precision bombing and to reduce civilian casualties in war. It was used by the army and the navy to pinpoint the location of troops and ships on land and sea to coordinate offensives and prevent friendly fire. Aircraft use it to stay on course. We use it to get around the world. This system was possible only because of the collaboration of many seemingly hostile nations, the rapid advances of modern technology, and our ability to take any military technology and give it away for public use. Yet so many of us take this revolutionary technology for granted. It can be difficult to acknowledge as amazing, but many of us couldn't imagine a life without GPS.
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