October 1959 Popular Electronics
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Albert Einstein published his paper on Special Relativity in 1905 and on General Relativity in 1916. Since that time, many experiments have been performed worldwide by scientists intent on both proving and disproving Mr. Einstein. Laser and nuclear based timepieces have been improved for precision and calculations refined to aid in the task. Nearly 100 years later, General Relativity stands. Even the rigors of quantum mechanics has not toppled its precepts.
Atomic Clock to Check EinsteinThere once was a Miss Fanny Bright
Whose speed was much greater than light
She set out one day
In a relative way
And arrived the previous night
According to Einstein's theory of relativity, if you were to travel in space for 20 years at the speed of light (186,000 miles per second), you would return to find the earth millions of years older. In the topsy-turvy world of relativity, where space and time merge into one and the same thing, the average person tends to be incredulous about the whole thing. But you can't argue about the existence of atomic bombs - which were developed according to Einstein's "theories." And now a most critical check of the special and general relativity theories is being planned.
Dr. Harold Lyons examines the tubular heart of the atomic clock which will be rocketed into space to test Einstein's two theories of relativity.
Dr. Harold Lyons, head of Hughes Aircraft's atomic physics department, is supervising the design of a 30-pound atomic "clock" which will be rocketed into space to "keep time" as it orbits around the earth through varying intensities of the earth's gravitational field. More accurate than any other time device in existence, the atomic clock will lose or gain less than one second in a thousand years. It bears no resemblance to an ordinary clock - having no arms or face - and in truth is more oscillator than clock. It looks something like a foot-long electron tube.
Before being launched, the atomic clock will be synchronized with a similar clock on the ground. Then, as it orbits through space at 18,000 miles per hour, it will generate an alternating current at a frequency of 24 billion cycles per second. For purposes of measurement, this extremely high frequency will be converted to a frequency more convenient for use with earth-based laboratory instruments. This information will then be radioed to earth and the time on the orbiting clock will be compared with the time on the earth clock.
It is expected that the satellite clock will run slow in comparison with the ground clock as it passes through orbits below 2000 miles because, according to the special theory of relativity, motional effects should predominate below that altitude. Above 2000 miles, the clock should run fast in order to bear out the general theory of relativity; at higher altitudes, the effects of the earth's gravity will be less.
Since the effects of motion and gravity are opposite, as the satellite goes through the 2000-mile point, they should cancel out and the two clocks should agree. Thus both the special and general relativity theories will be checked.
The importance of the experiment was pointed out by Dr. Lyons, who stated, "Any experiment that puts the general theory of relativity on a firmer physical basis would spur much significant work in the space and nuclear ages." With an actual clock-launching probably only several years off, the entire scientific world eagerly awaits the results.
Posted January 27, 2013