192 The Poetry of Physics and The Physics of Poetry
Several physicists around the world began working on the problem.
One of the groups consisting of Davisson and Germer attempted to
detect the wave behaviour of particles by scattering electrons off of
nickel. They were off to a flying start when their apparatus blew up and
they had to start practically from scratch. Luckily they were able to
salvage their target by treating it with heat. Their misfortune was actually
a blessing in disguise. As a result of the heating, the nickel target had
crystallized. When Davisson and Germer returned to their experiment,
they immediately observed a diffraction pattern identical to the one that
had been observed in earlier x-ray scattering experiments. There was no
doubt about it. The electron behaved exactly like a wave. It produced the
same diffraction pattern as x-rays. The paradox of quantum physics had
come full circle; not only did waves display particle behaviour but now
particles displayed wave behaviour. The wave behaviour of the electron
was displayed in other experiments following Davisson and Germer’s
success. The wave behaviour of neutrons was also discovered in a similar
diffraction scattering experiment with a crystal.
Long before Davisson and Germer had completed their experimental
demonstration of the wave nature of the electron, an Austrian physicist
named Erwin Schrödinger began developing de Broglie’s ideas of
standing matter waves. De Broglie’s work had been brought to his
attention by Einstein whom he thanks in a letter dated Zurich, April 23,
1926: “Besides, the whole thing would certainly not have originated yet,
and perhaps never would have, (I mean not from me), if I had not had the
importance of de Broglie’s ideas really brought home to me by your
second paper on gas degeneracy.” Schrödinger developed de Broglie’s
notion of standing matter waves to a much greater extent. De Broglie’s
standing waves were essentially one-dimensional circular waves.
Schrödinger considered the electron as a cloud, which filled the entire
space around the nucleus of the atom and vibrated as a three-dimensional
standing wave. Schrödinger developed a wave equation to describe the
electron, which took into account the electromagnetic force exerted by
the proton on the electron.
There is an amusing story told by Dirac related to Schrödinger’s
discovery of his famous equation. It seems that when Schrödinger
was originally developing his ideas the very first equation he derived
was a relativistic one. This equation has a number of complications.
Consequently, when Schrödinger applied this equation to the problem of
the hydrogen atom he was unable to obtain the desired experimental