Scientists study subatomic particles by examining the telltale trails, such as those shown here, their passage leaves behind in a bubble chamber. This image shows the first detection of a neutrino.
Click on image for full size
Argonne National Laboratory
Atomic Physics & Particle Physics
Atoms and the minute particles from which they are made strongly influence
the nature of many phenomena that play out their roles on astronomical scales.
The fields of atomic physics and particle physics provide many valuable insights
into the life cycles of stars, the forms of spaceborne radiation, and the way we
can use spectra to study distant objects.
The discipline of atomic physics concerns itself with atoms, the particles
from which atoms are made, and the various energy states that atoms can take
on. The tiny, dense nucleus of an atom is made up of protons and neutrons.
Clouds of electrons, less than a thousandth the size of the nucleons, buzz
around the nucleus in a complex array of energy states.
Particle physics delves into scales even smaller than the atom as it sheds
light on the worlds of subatomic physics. When atoms are torn apart, usually
in the presence of large amounts of energy, subatomic particles come out to
play. Some are familiar, such as protons, neutrons, and electrons; others are
more exotic, bearing strange names like muon, neutrino, baryon, meson,
and the elusive quark. Plasmas, such as the "soup" of electrons and protons
that makes up the solar wind, and many of the most dangerous forms of radiation,
such as cosmic rays, are collections of subatomic particles.
The "laws" of physics at atomic and subatomic scales are so different from
those we observe in our "normal" daily experiences that physicists had to invent
a whole new field to describe them. The discipline of quantum mechanics predicts the strange behaviors found
in the worlds of the very small. In the realms of quantum physics, the distinctions
between particles and waves disappear, we lose our ability to define the locations
of objects in favor of probabilistic descriptions of where particles are likely
to be, and the mere act of observing a phenomenon can fundamentally alter its
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