What is the difference between atomic and nuclear physics?
Asked by: Kelley D. Burroughs
What is the difference between atomic and nuclear
physics? Really short and non-informative answer
would be that one deals with atoms, while the other
deals with nuclei.
Of course, nucleus is a part of the atom. So what is
it that separates these two branches of physics? Atomic
physics deals with the properties of atoms, which are
mainly due to their electron configuration. The nucleus
is also involved, but only with its overall properties.
As far as atomic physics is concerned, the nucleus
is a single massive particle, with spin, mass, and charge.
The internal workings of the nucleus are irrelevant.
Nuclear physics, on the other hand, deals only with
nuclei. It studies the structure of nuclei, and their
reactions and interactions.
The distance scales involved are inherently different -
atomic physics deals with distances of the order of
nanometers - (10-9 m) while nuclear physics deals with
distances of the order of femtometers (10-15 m).
Also, energy scales involved in the two branches are
quite different. The energies involved in atomic physics
are in the 1 eV (electron volt) to 1 keV range. The energies
in nuclear physics are generally 1 MeV to 1 GeV. (Anything
higher may be considered elementary particle physics, but
it is hard to draw lines.)
These differences in scale and energies are due to differences
of the forces under study. Atoms are by and large governed
by electromagnetic interactions, where electrons
are bound at a typical distance of a fraction of
nanometers, with a typical energy of electron volts.
Nuclei, however, are bound by nuclear forces, which
are shorter ranged, yet much stronger than electromagnetic
forces - the typical binding distance is a femtometer,
with binding energies of a couple MeV per nucleon in
As a final note, the 'atom bomb' is probably a misnomer -
the energy released from the detonation of an atom bomb
is not due to an 'atomic reaction', but due to a
'nuclear reaction', where the nuclei are broken up.
So, 'nuclear bomb' is the better way of referring to it.
Answered by: Yasar Safkan, Ph.D. M.I.T., Software Engineer, Istanbul, Turkey
'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '