Physics

# Passenger Airplanes and the Theory of Relativity

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How Does the Theory of Relativity Apply to Plane Travel?

In his General Theory of Relativity, Einstein treats space and time as one four-dimensional object. He called this space time. In his theory he states that time is not absolute and flows differently for different observers. (Time does not flow when the universe is viewed as a whole. In essence it is timeless.) In his Special Theory of Relativity, Einstein states that an outside observer would see a clock on a moving object tick slower than one that is at rest next to him.

If we were to test this theory we would need two identical accurate time keepers, a fast moving vehicle (i.e a jet) and two observers to keep the clocks safe. Both clocks are checked and set to the same time. One observer boards the jet with one clock and the other observer stays on the ground with the other. Send the plane off on a long round trip. When the plane lands compare the clocks. The clock that was on the plane should be slower than the one that was left on the ground.

When you read further into this part of the Theory of Relativity, the loss of time on the plane should only occur when the plane is traveling eastward. The clock should gain time on a westward journey. This is to do with the earths rotation and gravitational forces.

Thanks to J.L.Hafele and R.E.Keating, who did a series of experiments in 1971, we have no need to find the equipment to do the above experiment ourselves. They took four Cesium atomic beam clocks and placed them on commercial jet flights around the world, first eastward, then westward. They used clocks at the U.S Naval Observatory as their ground reference clocks.

Using the planes flight plans and the Theory of Relativity, Hafele and Keating predicted that the clocks on the planes should have lost 40+/-23 nanoseconds during the eastward trip and gained 275+/-21 nanoseconds during the westward trip. In actual fact when the clocks were checked they had lost 59+/-10 nanoseconds on the eastward trip and gained 273+/-7 nanoseconds on the westward trip.

They proved that time does seem to flow differently in a fast moving vehicle than when we are at relative rest. Meaning people on a plane observe the passage of time differently than those at relative rest on the ground, just as Relativity suggests.

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