An Etymological Dictionary of Astronomy and Astrophysics

A subatomic particle that, according to the uncertainty principle, comes into being out of energy fluctuations of the “vacuum” and lasts for extremely short periods of time. An electron-positron pair can exist only about 4 x 10^-21 seconds. The lifetime increases as the mass and energy involved decreases. Virtual particles are real and have measurable effects, but cannot be directly observed, according to the uncertainty principle. → vacuum polarization.

See also: → virtual; → particle