In the context of the book The Planet of the Apes by Pierre Boulle (also a big-budget 1968
movie by Franklin J. Schaffner and starring Charlton Heston, and a more recent
film), we see an early popular understanding of time dilation serve as a major
plot device. The relativity of time was
used as a convenient method for allowing travel to a distant star system. It was imagined in 1963, amidst frenzied advancement
in astronomy, and so placed its opening timeframe perhaps only a few decades
into the future.
Professor Antelle, a genius scientist, has invented a
special spacecraft that is able to move at such a high velocity (via unknown
propulsion) that time itself is slowed significantly for the pilot. This obviates the problem of impossibly low
interstellar speed, and allows a huge amount of space to be traversed in even
“less” time (from the pilot’s point of view) due to time dilation. Ulysses, the main character, is part of the
expedition, along with the professor, and Levain, a physician.
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| Time dilation versus velocity |
They intend to use this spaceship to travel to the nearest
place they believe that extraterrestrial life may exist- a star system whereof
the supergiant Betelgeuse is the local sun.
The time it would take their ship to reach there is 350 years, but for
the individuals inside, the time will feel like a mere two years. What velocity does this entail? Rearranging the above equation for known
values:
In order for time dilation to be that potent,
one must get very close to the speed
of light. As we can see, earthly
technology brings us nowhere close to even this velocity which would only shrink time by a factor of 175. In order to reach space millions or billions
of light-years away, the only possibility is to get even closer to the speed of
light.
The
practical difficulty is not so much in what a person would do for years on a
spaceship (although this is a bit mind-boggling) but the quantity of energy it
would take to transport anything at speeds close to that of light. The kinetic energy of an object traveling at
the speed of light is phenomenal. The
craft described in the book is not miniscule, either. Let us say, for example, that using
miraculous miniaturization technologies that the spacecraft can be able to
carry its engines, three passengers, and enough supplies for two years forward,
two years back- in a mass no greater than that of the Space Shuttle.
This figure is a bit large, to say the least. If this spaceship spread out its acceleration
over the ridiculously long interval of 20 days, then the power required would
be:
which is equal to 3.8 billion horsepower. If it were to accelerate to that speed in the
same time that it took for the Shuttle to clear the atmosphere, then over one
trillion horsepower would be required.
The
conclusion I draw from this is that, in order for humans to attain speeds close
to that of light, the mass involved must be infinitesimal enough so that the
energy can be produced to power it, or else new methods of power (e.g. not
derived from chemical or electrical propulsion) must be found.
But
audiences would never have suspected this in the optimistic year of 1963, and
as The Planet of the Apes shows, it was not a picnic when the light-speed
travelers arrived at their destination.
Society involved the subjugation of humans by their primate
overlords. When our hero Ulysse finally
fled, and returned to Earth, 700 years had passed and the same fate of human
enslavement had befallen his planet.
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