American physicist who, with David J. Gross (Gross, David J.) and Frank Wilczek (Wilczek, Frank), was awarded the Nobel Prize for Physics in 2004 for discoveries regarding the strong force—the nuclear force that binds together quarks (quark) (the smallest building blocks of matter) and holds together the nucleus of the atom.

Politzer studied physics at the University of Michigan (B.S., 1969) and Harvard University (Ph.D., 1974). In 1975 he began teaching at the California Institute of Technology, and from 1986 to 1988 he served as head of the school's physics department.

In the early 1970s Politzer—along with Gross and Wilczek, who were pursuing parallel research at Princeton University—used particle accelerators to study quarks and the force that acts on them. (See fundamental interaction.) They discovered that quarks were so tightly bound together that they could not be separated as individual particles but that the closer quarks approached one another, the weaker the strong force became. When quarks were brought very close together, the force was so weak that the quarks acted almost as if they were free particles not bound together by any force. When the distance between two quarks increased, the force became greater—an effect analogous to the stretching of a rubber band. This phenomenon became known as asymptotic freedom, and it led to a new physical theory, quantum chromodynamics (QCD), to describe the strong force. QCD completed the standard model, a theory that describes the fundamental particles in nature and how they interact with one another.

Politzer had a featured role in the film Fat Man and Little Boy (1989), a fictional look at the Manhattan Project.