The question you might ask next is: well, how does this global positioning technology work today? There are three main keywords that are essential to understanding how GPS technologies work in our world today. It's about trilateration, synchronization, and time travel... yes, time travel. To begin with, the basic concept of the Global Positioning System is to have a minimum of 24 operational satellites orbiting at an altitude of approximately 24,000 km above the Earth and traveling at an orbital speed of approximately 14,000 km/hour. At any time there are always at least 4 satellites “visible” on your receiver (e.g. iPhone). The receiver then gets information from at least 3 of these 4 satellites and uses what is called trilateration to determine your exact location on the surface of the Earth. Trilateration, according to the Encyclopedia Britannica, is a “surveying method in which the lengths of the sides of a triangle are measured and the angles are calculated from this information. By constructing a series of triangles adjacent to each other, a surveyor can obtain other distances and angles that would otherwise be unmeasurable.” To keep things simple, trilateration is the method by which 3 satellites send a signal to a receiver which then calculates the distance to each and the time the signal was sent. The timing part of this process is essential and will be explained later. The receiver then compares these 3 or even 4 signals and finds the common intersection between them, essentially determining where the GPS user is located. The basic concept of how the Global Positioning System works seems extremely simple, however what happens behind the scenes includes processes that get particularly confusing... half the paper... day. On the other hand, Einstein's theory of General Relativity basically states that clocks closer to a large mass will appear to slow down compared to those isolated in space. As a result, clocks down here on earth tick faster than those farther away. And in this case the satellites are located about 24,000 km above the Earth, which means that the clocks found inside the satellites would be ahead of ours by about 45 microseconds per day. With some basic math, we can calculate 45 and subtract 7 to get the magic number of 38, which is the time the satellite clocks beat each day. To compensate for this natural error, engineers slow down the ticking frequency of atomic clocks placed on satellites before they are put into orbit. Satellites literally travel in time so we can find our way to the nearest gas station when we get lost.