Professor Wilhelm Roentgen was fascinated by the
mysterious illumination produced by an electric discharge
in a tube without any air. The illumination
seemed to start at the
negative electrode, or "cathode".
Accordingly, the phenomenon was referred to as
"cathode rays". When the rays hit the glass of the
tube, it glowed with a greenish light.
On November 5, 1895, Roentgen enclosed his cathode
ray tube in a box of black cardboard and
darkened the room. He wanted to observe the luminescence
without the interference of outside light.
He turned on the electricity. Almost at once a flash
of light that did not come from the tube caught his
eye. He looked up.
Quite a distance from the tube, he
happened to have a sheet of paper coated with a
chemical, barium platinocyanide. He had been using
the paper in
experiments because this was one of the
chemicals that glowed when
placed near the cathode ray tube.
wny should it be glowing now? After all, the
tube was in a cardboard box!
Roentgen walked into the next room with the coated
paper, closed the door,
and pulled down the blinds.
Still the paper continued the glow
so long as the tube was in
had discovered something invisible that acted
through cardboard and walls!
Wilhelm Roentgen was born on March 27, 1845, in
Lennep, a small town in Germany. For most of his
early life, however, he lived outside Germany. He
received his primary education in Holland and went to
college in Switzerland.
After completing his college course, Roentgen continued
his studies in Switzerland, concentrating on
research in physics. In 1888 a new
institute of physics was
opened at the
University of Wurzburg in Bavaria,
and Roentgen was invited there. It was there that he
discovered his penetrating rays and won world fame.
His mysterious rays, which penetrated cardboard
and doors, causing chemicals to luminesce, were
called "Roentgen rays" in honour of their discoverer.
Roentgen himself, in view of their mysterious origin,
. gave his rays the
mathematical symbol for the unknown.
He called them "X-rays", the name by
which they are commonly referred to in English.
As we have
seen in previous chapters of this book,
careful investigations of some phenomenon often result
in unexpected discoveries of related, but previously
unknown phenomena. To an outsider
often seem accidents or luck. But, as Pasteur once
remarked, in science chance favours the prepared
mind. The mind must be prepared in two ways. It
must know the subject very well, well enough to
recognize something new
when it turns up.
it must also be receptive to
something new or strange. There is only a narrow line between the
understandable refusal of a
scientist to be distracted by side effects
and a willingness to notice and to
strange or annoying effect in an
experiment. In the last
decades of the nineteenth century there
were many scientists
with more or less "prepared minds" working
with cathode rays. But the
astonishing discovery of
X-rays was made by a man both lucky and wise -lucky
enough to observe something peculiar (although
oihers had already observed it)
and wise enough to
announced his discovery, the scientific
world was amazed. A number of scientists found
that they had encountered these
mysterious rays earlier.
William Crookes, a British scientist who had worked
with cathode rays, had noticed several times that photographic
film nearby had become fogged." He had
accidental and paid no
attention. In 1890
American physicist, had actually
produced what we now call an X-ray
he was not sufficiently interested to follow it up and
the nature of the phenomenon.
a few weeks of his discovery, Roentgen was
-able to establish many important
characteristics of X-rays.
He demonstrated that X-rays have a much
penetrating power than cathode rays and that they are not
bent by magnetic or electric fields.
Usually years or even decades pass between a new
scientific discovery and its
practical application. But
with X-rays the applications came
discovery was made in November, 1895.
His first publication
on the subject appeared in December. And already
in January, 1896, the broken arm of an American,
Edward McCarthy, was set with the help
Soon X-rays were in common use in medical practice.
Doctors now had a way of looking into the
quickly, easily, and — above all —
breaks in bones
could be discovered, the beginnings
of tuberculosis in the lungs, foreign objects in the
in short, the doctor had a magic eye at his disposal.
industry, too, X-rays have applications. They can
detect internal flaws in the structure of metals,
flaws that would
be invisible otherwise. In chemical
research they are used to probe the structure of crystals and of
complex molecules, for example, of
proteins. In short, Roentgen's discovery provided a new means
of making the invisible visible.