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.
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Argonne National Laboratory

Atomic Physics & Particle Physics

Atoms and the tiny particles from which they are made strongly influence the world around us. The fields of atomic physics and particle physics help us understand the life cycles of stars, the forms of radiation in space, 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.

Last modified September 12, 2008 by Randy Russell.

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