The phrase "the driver is lost, be late" is disappearing. Many vehicles begin to incorporate a GPS (Global Positioning System) that lets us know where we are on Earth to within a few meters and can suggest a route not to be late. The GPS also allows a plane to fly almost pilot a ship to know their position at sea or determine how they are shifting the tectonic plates that make up the continents. We've all heard of this new technology without being aware that their work requires theories of Special Relativity (1905) and General Relativity (1915) of Albert Einstein.
The fundamental idea is that both theories help us understand how the time is measured by different watches. The operation of a GPS device is based on receiving signals from different clocks whose location is known and derive its own position from this information. To this end, thirty satellites orbiting the Earth. Each satellite carries a cesium atomic clock precision almost unimaginable: a tic every nanosecond ago and only delayed about 4 nanoseconds per day. The reason for such overwhelming accuracy is easy to understand. Light travels about 30 cm every nanosecond. If we want to accurately determine a position a few meters using electromagnetic signals from satellites, we measure time with an error less than about 20 nanoseconds. We need accurate clocks well synchronized. Here comes
Relativity. Time is not equal to a clock on a satellite to another we have at home. Here are two reasons. A, the clock in orbit is moving relative to our approximately 12 000 km / s. Two, our watch is immersed in an intense gravitational field. In the first case, the Special Theory of Relativity predicts the clock in orbit is delayed about 7 microseconds per day on the clock in our house. In the second case, the General Theory of Relativity dictates that the clock in orbit is ahead about 45 microseconds per day. Both effects combine so that, if not corrected, clocks are out of sync about 38 microseconds per day. In other words, if we do not use relativity, our GPS is useless after two minutes. After a day, would our position with an error of 10 km.
GPS incorporates, therefore, the equations of relativity! In fact, the orbiting clocks were set at the factory to make their tics more slowly and thus correct some of the relativistic effects mentioned above. It's a great history lesson: Einstein's theory, motivated by the need to unify the paradigms of classical physics and electromagnetism has led to a technological tool whose impact we begin to see.
We can speculate about the social impact of GPS. Combining GPS with the issuance of a signal can remotely monitor the position of any object. There are tracking systems for cars that may extend to all types of objects or people. The vision of a Big Brother who knows where every human being terrified me. It is urgent to initiate legislation limiting the use of GPS. Is it ethical to monitor the position of a worker? How a child? Like other times in the history of science, conceptual achievement means that we should use technology with agreed criteria and containment.
The GPS system operates under the control Department of Defense U.S.. Because relativity belongs to no one, Europe is building Galileo, its own civil GPS. Public investment in basic science is at least two justifications: their unpredictable fruit are produced on time frames greater than the need to return a company and also the knowledge gained must be public and non-proprietary.
The future will be a thousand times more fascinating to glimpse. Atomic clocks have a hundred thousand times more accurate than those used in the GPS system will stabilization, miniaturization and cheaper and that will locate an object with an accuracy of 1 cm. That object could be a car without a driver.
More than one young reader will be devising an original use of GPS, capable of providing the needed value. Without basic science, there is no further development or innovation. Quantum mechanics also awaits. The study and construction of atomic lasers will lead to slow quantum waves, capable of measuring distances with greater accuracy. (Younger readers, study quantum mechanics.)
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