Collapsing Atoms
In 1898 Henri Becquerel had discovered an entirely new
physical phenomenon - radioactivity. This growth area in physics rapidly led to
the realisation that atoms were not simply inert billiard balls. On the
contrary, they have an internal structure. By the end of the first decade of
the 20th Century sufficient research had accumulated for physicists to be able
to begin making models of this structure. It was clear that atoms had a very
small, dense, positively charged nucleus surrounded by negatively charged
electrons.
Ernest Rutherford proposed a planetary model for the atom -
electrons in orbit around a nucleus like planets around a star. The fly in the
ointment was electromagnetism. An electric charge moving in a circle emits
energy. If electrons are classical particles emitting energy in this way, they
would very rapidly dissipate all their energy and fall into the nucleus.
A solution was offered by a young Danish physicist, Niels Bohr
(see model and metaphor). The
key was the abandonment of continuity in favour of quantisation. Bohr simply
ruled out the possibility of electrons occupying every possible orbit. Instead
they are confined to certain discrete energy levels. Although outlandish, his
suggestion had the added attraction that it explained another anomaly - the
fact that the light emitted by hot gases is emitted only at certain frequencies
(spectral lines).
Email
link | Feedback | Contributed by: Dr.
Christopher Southgate
Source: God, Humanity and the
Cosmos (T&T Clark, 1999)
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