October 1959 Popular Electronics
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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 Einstein
There once was a Miss Fanny Bright
Whose speed was much
greater than light
She set out one day
In a relative
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
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