Number 214 (Story #3), February 16, 1995 by Phillip F. Schewe and Ben Stein TABLETOP TESTS OF ELECTROWEAK THEORY have been performed with thallium atoms. The theory holds that an atom's electrons interact with its nucleus through the electromagnetic force (by the exchange of photons) and, at a much weaker level, through the weak force (principally by the exchange of Z bosons). Working independently, a team at Oxford, UK, and a University of Washington team (contact Norval Fortson, 206-543-2665) carefully observed what happened to laser light when it passes through a thallium vapor. Among other things, both groups measure Q, the value of the "weak charge" (somewhat analogous to electric charge) of the thallium nucleus as seen by its outermost electron. These and other measurements of parity violation (the weak force, unlike the electromagnetic force, differentiates between left and right) in atoms do not yet yield electroweak values that rival in precision those obtained at particle accelerators, but this may change if theorists could provide a more precise picture of the quantum behavior of the electron (as described by its wavefunction) in the thallium atom. (P.A. Vetter et al. and N.H. Edwards et al., upcoming articles in Physical Review Letters.)