2 3 2 D O C . 2 3 6 T H E C O M P T O N E X P E R I M E N T
sudden change of direction when reaching surfaces. By using this fundamental no-
tion, a quite complete theory was created for almost all phenomena known up to
then, particularly those involving the telescope and the microscope.
But when some one hundred years ago one became better acquainted with the
phenomena of interference and diffraction (along with the polarization of light), it
became necessary to replace Newton’s fundamental assumption about the nature of
light with the entirely different one of the wave theory, which had been postulated
already some one and a half centuries earlier by Huygens. According to it, light
would consists of elastic waves that propagate outwards in all directions through
space (i.e. the ether) similarly to the propagation of waves in two dimensions at the
surface of water when they are set into oscillatory motion from single point on that
surface. It was only this theory that succeeded in clarifying why a ray of light prop-
agates in all directions after passing through a very narrow opening. Only this the-
ory can explain why there are dark spots in interference and diffraction effects in
the middle of an area of space flooded with light, or why many bundles of light can
locally cancel out one another’s effect. This wave theory was able to represent the
complicated phenomena of diffraction and interference with downright astronom-
ical precision, thus cementing the conviction of its correctness.
The wave theory was modified and, at the same time, given even firmer ground-
ing through the investigations of Faraday and
Maxwell,[2]
according to which the
wave field was divested of its mechanical character. Maxwell’s theory of electricity
and magnetism also encompasses the wave theory of light without altering any of
its formal content. This theory establishes quantitative relationships between the
optical and electrical behavior of empty space as well as of ponderable bodies, and
reduces the number of mutually independent hypotheses upon which wave optics
is based. Thus, around the turn of the century, physics seemed to possess a founda-
tion that it was hoped could forever serve as a basis for all its subfields, including
mechanics.
But it happened otherwise. From
Planck’s[3]
papers about the law governing the
radiation emitted by hot bodies it emerged that the theory was unable to explain this
law. Neither could one explain the general finding that the effects of the radiation
depended qualitatively not on the latter’s intensity but only on its color. This is
highly paradoxical and seems to be incompatible with the fundamental idea of the
wave
theory.[4]
Imagine huge waves generated somewhere on the open sea spread-
ing out in all directions from the center of excitation. Naturally, the wave peaks
generated this way will not be as high the farther away they have propagated from
the center of agitation. Now imagine equally sized ships distributed over that area
of the ocean before the afore-mentioned waves are generated. What will happen