Two of the most frustrating things about driving a car are getting lost and getting stuck in traffic
While the computer revolution is unlikely to cure these problems, it will have a positive impact.
Sensors in your car tuned to radio signals from orbiting satellites can locate your car precisely at
any moment and warn of traffic jams. We already have twenty-four Navstar satellites orbiting the
earth, making up what is called the Global Positioning System. They make it possible todetermine
yourlocation on the earth to within about a hundred feet. At any given time, there are several GPS
satellites orbiting overhead at a distance of about 11,000 miles. Each satellite contains four
"atomic clocks," which vibrate at a precise frequency, according to the laws of the quantum theory.
As a satellite passes overhead, it sends out a radio signal that can be detected by a receiver in a
car's computer. The car's computer can then calculate how far the satellite is by measuring how long
it took for the signal to arrive. Since the speed of light is well known, any delay in receiving the
satellite's signal can be converted into a distance.