Descriptionary

boson any of a class of subatomic particles, includ­ing mesons, weakons, classons, and photons, that do not obey the Pauli exclusion principle. All particles are either bosons or fermions.

carbon dating a technique for determining the ages of substances or objects that contain carbon by mea­suring how much carbon 14 remains in them.

carbon 14 a radioactive isotope of carbon, hav­ing a half-life of 5,730 years, and subsequently used to determine the age of carbon-containing fossils, archaeological artifacts, and so forth.

CERN Center for European Nuclear Research; an international accelerator facility near Geneva, Swit­zerland.

chain reaction a series of self-sustaining nuclear reactions.

charm a characteristic in particles that predicts the lack of reaction between certain particles and that accounts for the long life of the J particle.

classon either a photon or a graviton, which have neither mass nor charge.

cold fusion hypothetical method of creating unlim­ited energy by fusing atoms in a test tube with much lower temperatures and pressures than traditionally believed to be possible.

collider an accelerator that creates two beams of charged particles that collide head on, used for research and experimental purposes.

color the distinguishing characteristic of quarks that determines their behavior in the strong interaction.

cosmic rays particles of energy radiating from space.

critical mass the minimum amount of fissionable material needed to cause a nuclear explosion.

curie a unit of radioactivity equal to the quantity of a radioactive isotope that decays at 37,000,000,000 disintegrations per second.

cyclotron a circular accelerator in which particles in a magnetic field are propelled by alternating high- frequency voltage, to study interactions.

dalton an atomic mass unit.

decay a process in which a particle gradually dis­appears and is replaced with a different particle or particles.

deuterium an isotope of hydrogen.

deuteron the nucleus of deuterium, used in accel­erator collisions of particles for research purposes.

E = mc² Albert Einstein's formula, energy equals mass multiplied by the velocity of light squared, which can be used to explain the loss of mass in a nuclear reaction and its ultimate conversion to energy.

electron a subatomic particle or lepton with a nega­tive charge. A cloud of electrons surround an atomic nucleus.

dose a quantity of radiation absorbed by a body.

dosimeter a device containing photographic film, which darkens the more it is exposed to radiation. It is worn and monitored by people who work around radiation sources. Also known as a film badge.

electromagnetic force one of the four fundamental forces of nature, the interaction between particles caused by their electric and magnetic fields. Also known as electromagnetic interaction.

electron a negatively charged particle that moves around the nucleus of an atom.

electroweak force the combined effects of the elec­tromagnetic and weak forces.

elementary particle any indivisible subatomic par­ticle in a nucleus, such as a lepton, quark, weakon, or classon.

exclusion principle the law of physics that states that no two identical particles can have the same set of quantum numbers or occupy the same quantum state. More formally known as the Pauli exclusion principle.

fast neutron a neutron that can produce fission.

Fermilab the Fermi National Accelerator Labora­tory in Batavia, Illinois.

fermion a subatomic particle with peculiar angular momentum or spin and which cannot exist in the same state simultaneously as any other fermion. Elec­trons, protons, neutrons, quarks, and leptons are all fermions.

film badge see dosimeter.

fissile fissionable. The isotopes uranium 235 and plutonium 239 are highly fissile.

fission a nuclear reaction through which an atom is split, releasing massive energy.

flavor designating any one of the types of quarks or leptons. in quarks, the flavors are up, down, charm, strange, top, and bottom. In leptons, the flavors are electron, muon, tau, electron neutrino, muon neu­trino, and tau neutrino.

fundamental interaction any one of the four fun­damental forces of nature—electromagnetic, weak, strong, and gravitational.

fusion a nuclear reaction through which two atoms combine to form another element, releasing massive energy. It is the primary energy of stars.

gamma ray electromagnetic radiation with a high penetration power, produced by nuclear reactions.

Geiger counter an instrument used to detect and measure the presence of ionizing particles.

gluon a massless subatomic particle that binds quarks through strong force to form hadrons, such as protons and neutrons.