The most startling example of this is
the Twin Paradox, today science fiction but one day certain to become
reality. A man sets out for a distant star at close to the speed of
light, leaving his twin brother back on Earth. Eventually he returns
home---to find his brother twice as old as he is. This will not be an
illusion to be explained by psychologists, but a physical fact.
Yet the twins were born on the same
date, so how could their ages now differ? After all, the Earth is also
moving at high speed through space. The answer is plain. When the
stay-at-home twin moves, the entire universe moves with him. But when
the astronaut twin moves, he moves alone.
A German book appeared in the 1920s
called 100 Scientists Against Einstein. Nearly all of them
ignored the point in the above paragraph.
And why does the astronaut age
more slowly? It is because of the strange behaviour of light. It always
travels at the same speed, 670 million mph. If, for example your
spaceship was rushing towards a star at half the speed of light, you
might expect the star's light to reach you at 1.5 times the speed of
light. But it doesn't. It arrives at its same, constant speed. You can
only conclude that your clocks are running slowly.
But logical though the case may be, by
the time that we have the technology to travel at near the speed of
light, many people will still find it impossible to believe that someone
who travels fast enough can be younger than his own children. It will
seem utterly at variance with everyday experience. And churchgoers will
no doubt be singing the old hymn with its beautiful wording but with its
erroneous Newtonian message:
Time, like an ever-rolling stream,
Bears all its sons away.
It has happened before, this clash
between reason and common sense. When Columbus asked the King and Queen
of Spain to fund his voyages, the two monarchs set up a committee of
scholarly experts who rejected with contempt the idea that the Earth was
round.
``Is there anyone so foolish as to
believe that there are antipodes opposite to ours?'' the committee
asked. ``That there are people who walk with their heels upwards and
their heads hanging down?''
Like the opponents of Einstein, these experts were
displaying common sense, that most dangerous enemy of creative thought.
As the great mathematician Alfred North Whitehead remarked, ``common
sense can only act to suppress originality.'
