The Science Book

(Elle) #1

A PARADIGM SHIFT 209


found an unexplained radiation.
What were these new radiations
and where were they coming from?
Becquerel correctly surmised
that this radiation was emanating
from within uranium salts.
When Pierre and Marie Curie
studied the decay of radium,
they discovered a constant and
seemingly inexhaustible source of
energy inside radioactive elements.
If this were the case, it would
break several fundamental laws of
physics. Whatever these radiations
were, it was clear that there were
large gaps in current models.


Discovery of the electron
The following year, the British
physicist Joseph John (J. J.)
Thomson caused a sensation when


See also: John Dalton 112–13 ■ August Kekulé 160–65 ■ Wilhelm Röntgen 186–87 ■ Marie Curie 190–95 ■
Max Planck 202–05 ■ Albert Einstein 214–21 ■ Linus Pauling 254–59 ■ Murray Gell-Mann 302–07


J. J. Thomson is pictured here at
work in his Cambridge laboratory.
Thomson’s “plum pudding” model
of the atom was the first to include
the newly discovered electron.

he demonstrated that he could
break lumps out of atoms. While
investigating the “rays” emanating
from high-voltage cathodes
(negatively charged electrodes), he
found that this particular kind of
radiation was made of individual
“corpuscles,” since it created
momentary, pointlike sparkles of
light on hitting a phosphorescent
screen; it was negatively charged,
since a beam could be deflected
by an electric field; and it was
exceedingly light, weighing less
than a thousandth of the lightest
atom, hydrogen. Moreover, the
weight of the corpuscle was the
same, no matter which element
was used as a source. Thomson
had discovered the electron. These
results were totally unanticipated

theoretically. If an atom contains
charged particles, why shouldn’t
the opposing particles have equal
mass? Previous atomic theories
held that atoms were solid lumps.
As befit their status as the most
basic constituent of matter, they
were entire, whole, and perfect.
But when viewed in the light of
Thomson’s discovery, they clearly
were divisible. Put together,
these new radiations raised
the suspicion that science had
failed to understand the vital
components of matter and energy. ❯❯
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