Cornell, Eric Allin (1961-…), an American physicist, won a share of the 2001 Nobel Prize in physics for discovering and studying a state of matter known as a Bose-Einstein condensate (BEC). A BEC is a cluster of atoms that behave somewhat as if they were a single atom. Cornell shared the prize with his colleague, the American physicist Carl E. Wieman; and with the German physicist Wolfgang Ketterle, who worked separately on BEC’s. The condensates are named for the physicists Satyendra Nath Bose of India and Albert Einstein of Germany, who proposed in the 1920’s that BEC’s could be created.
The creation and behavior of a BEC can be explained in terms of the wave-particle duality of matter. We commonly consider an atom to be made up of solid particles. But an atom also has properties of a wave. One of those properties is wavelength, the distance between successive wave crests. The wavelength of an atom depends on the atom’s momentum—_that is, its total amount of motion. The smaller the momentum, the larger the wavelength. An atom’s momentum equals the _mass of the atom times the atom’s velocity. The atom’s mass is its amount of matter; its velocity is its speed in a particular direction.
Cornell and Wieman created BEC’s by decreasing the velocity of atoms in a gas. As the velocity decreased, the wavelengths of the atoms became larger. Eventually, the wavelengths became approximately as large as the distances between the atoms. When that occurred, all the atoms suddenly began to move at one velocity. The entire cluster of atoms took on the properties of a single wave, thereby becoming a BEC.
Cornell and Wieman created their BEC’s in a gas consisting of rubidium atoms. The scientists cooled the gas to less than 35 billionths of 1 degree Fahrenheit above absolute zero (–459.67 °F or –273.15 °C). Cooling a gas is equivalent to decreasing the velocity of its atoms; the temperature of a gas is a measure of the average energy of motion of its atoms.
The scientists decreased the velocity of the rubidium atoms by bombarding them with light. According to wave-particle duality, light can be thought of as consisting of waves or of particles called photons. A photon has zero mass, but it possesses momentum. Cornell and Wieman forced photons to collide head-on with the rubidium atoms, thereby slowing those atoms.
Cornell was born in Palo Alto, California, on Dec. 19, 1961. In 1990, he obtained a Ph.D. degree in physics at the Massachusetts Institute of Technology (MIT) in Cambridge. Since 1992, he has been a physicist at the National Institute of Standards and Technology (NIST) in Boulder, Colorado. In 1992, Cornell also became an adjoint assistant professor at the University of Colorado in Boulder. He became an adjoint professor in 1995. An adjoint professor is a faculty member who is employed by another institution.
Cornell and Wieman first created BEC’s in 1995 at JILA, a research institute operated jointly by NIST and the University of Colorado. JILA was originally known as the Joint Institute for Laboratory Astrophysics. Today, only the abbreviation is used.
