BUT HERE’S THE THING. The atomic clock has to be very accurate so it can tell your smartphone where the GPS and the phone are with respect to each other. A ship at sea, for instance, has to know its latitude and longitude with precision, so it can navigate to its destination.  Einstein’s theory of relativity — verified many times — says that rapidly moving clocks such as those in the satellites, tick more slowly than clocks on Earth, by about seven-millionths of a second per day. Also, the orbiting clocks are 12,000 miles above the Earth, so they feel gravity that is about four times weaker than clocks on the ground. Einstein’s theory of Special Relativity —also verified many times — says that the orbiting clocks will tick faster by about 45 millionths of a second per day. Since these atomic clocks must synchronize with each other, as well as with clocks and smartphones on the ground, Einstein’s corrections must be applied continuously, or else your navigational error will accumulate by about 6 miles a day.

So the next time your plane lands safely in bad weather, or your smartphone tells you to turn left in 700 feet, give thanks to the genius — and yes to the Patron Saint of the GPS system — Albert Einstein.

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GPS

YOU MAY BE SURPRISED to learn that if you use or carry a smartphone, you are also using and carrying Albert Einstein around with you. Yes, it’s true. His theories, confirmed many times by sophisticated experiments done all over the world by clever dedicated physicists, make your smartphone a living heroic embodiment of Einstein!

LET ME EXPLAIN.
Up above us, circling the Earth twice a day at an altitude of about 12,000 miles, zipping along at about 8,700 miles per hour, are 24 satellites containing precise atomic clocks. These depend on the fixed basic vibrational frequencies of atoms inside the clock. These vibrations ensure that the atomic clock is accurate to 50 billionths of a second. They allow the satellite to communicate their location and distance from your smartphone to an extra-ordinarily high degree of accuracy. They were originally designed and built for military navigation at a cost of about ten billion dollars, and now we use them every day when we insert an address and get directions. The smartphone communicates with the GPS, and the GPS communicates with the smartphone. They are partners. Colleagues. Tight colleagues. Very tight.

BUT HERE’S THE THING. The atomic clock has to be very accurate so it can tell your smartphone where the GPS and the phone are with respect to each other. A ship at sea, for instance, has to know its latitude and longitude with precision, so it can navigate to its destination.  Einstein’s theory of relativity — verified many times — says that rapidly moving clocks such as those in the satellites, tick more slowly than clocks on Earth, by about seven-millionths of a second per day. Also, the orbiting clocks are 12,000 miles above the Earth, so they feel gravity that is about four times weaker than clocks on the ground. Einstein’s theory of Special Relativity —also verified many times — says that the orbiting clocks will tick faster by about 45 millionths of a second per day. Since these atomic clocks must synchronize with each other, as well as with clocks and smartphones on the ground, Einstein’s corrections must be applied continuously, or else your navigational error will accumulate by about 6 miles a day.

So the next time your plane lands safely in bad weather, or your smartphone tells you to turn left in 700 feet, give thanks to the genius — and yes to the Patron Saint of the GPS system — Albert Einstein.

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