Physics Terms

ATOMS The basic units of ordinary matter consist of one or more electrons circling a tiny, dense nucleus of protons and neutrons.

DARK MATTER Invisible matter that seems to provide the gravitational glue to assemble galaxies and other large cosmic structures, according to astronomical measurements.

FERMIONS Particles that form the basis for what we normally think of as matter. Elementary fermions are divided into two categories, leptons and quarks (see below). Protons and neutrons are also fermions.

HADRONS Particles made of more than one quark, like protons or neutrons, which have three, and mesons, which have two.

HIGGS BOSON The building block of the Higgs field, which imbues other elementary particles with mass.

HIGGS FIELD A field of energy said to permeate space and to imbue elementary particles with mass.

LARGE HADRON COLLIDER A particle accelerator at CERN, outside Geneva, that collides bulky hadrons like protons and lead ions.

LEPTONS Lightweight particles like the electrons that constitute electrical current and their relatives, and three kinds of neutrinos (see below).

NEUTRINOS Extremely light, almost massless, invisible particles produced in radioactive decays, they are part of the lepton family and come in three kinds.

NEUTRONS Electrically neutral particles found in the atomic nucleus along with protons. Like protons they are made of quarks.

STANDARD MODEL A set of equations that describes forces of nature in terms of elementary particles, known as fermions, interacting by tossing blobs of energy called bosons at one another in a sort of cosmic game of catch. In this theory, matter has been further subdivided. Fermions are divided into six kinds of quarks and six kinds of lighter particles like electrons and neutrinos called leptons.

SUPERSYMMETRY A hypothetical property of nature relating matter particles (fermions) and force particles (bosons). For each particle in one group, there would be a corresponding superpartner, as yet undiscovered, in the other group. The result would be to double the number of kinds of elementary particles in the universe.

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