Prelude to Relativity 119
the stationary car and the moving car, we would surely think that the
light from the headlights of the moving car would have a greater velocity
than the light from the headlights of the stationary car. This conclusion,
which we have reached intuitively, can also be supported logically by
arguing in the following manner: If we must add the velocity of the car
to the velocity of the ball, then we should add the velocity of the car to
the velocity of light. The conclusion that the velocities of the car and
light should add, nevertheless, contradicts the results of the Michelson–
Morley experiment. Although this contradicts both our logic and
intuition, it becomes apparent the one way to explain the negative result
of the Michelson–Morley experiment is to assume that the velocity of
light is independent of the velocity of the source of the light or of the
observer.
The reason that it was so difficult for Fitzgerald, Lorentz, and their
contemporaries to arrive at Einstein’s simple, literal interpretation of the
Michelson–Morley experiment was that it violated their intuition. For
them, Einstein’s conclusion wasn’t natural. We experience the same
discomfort in understanding and accepting Einstein’s Theory of
Relativity for it violates our intuition as well. His theory is based on the
apparent paradox that the velocity of the car plus the velocity of light is
equal to the velocity of light. But if Einstein’s Theory of Relativity
violates our intuitive notions of space, time and motion, why should we
accept his interpretation rather than the Lorentz–Fitzgerald one? The
reason is simply that the Lorentz–Fitzgerald interpretation represents
a dead end. It is an ad hoc explanation of the Michelson–Morley
experiment, which, aside from the increase of mass, did not make any
other predictions, which could be tested experimentally. Einstein’s
interpretation led to a theory, which made a number of measurable
predictions. All of the experimental tests that have so far been performed
have all corroborated Einstein’s Theory of Relativity.
Since the purpose of a scientific theory is to explain empirical
observations rather than reinforce our intuitions, the choice of inter-
pretation is obvious. We must learn to live with what seems to us an
apparent paradox. If we consider for a moment, however, that our
intuition concerning the addition of velocities developed only through
the consideration of velocities, much less than the velocity of light,
perhaps we may resolve this paradox. After all, the greatest velocity, any
of us experienced was the speed of an airplane that is less than the speed
of sound, which is only 300 m/sec or approximately one-millionth the