Number 29 (Story #1), April 11, 1991 by Phillip F. Schewe and Ben Stein GRAND UNIFIED THEORIES of particle physics predict that at very high energies (1015 GeV), or equivalently at very early times after the Big Bang, the electromagnetic, weak, and strong forces should be comparable in strength. At the lower energies available at particle accelerators, the relative strengths of the forces are expressed as three "coupling constants." Using data at the LEP electron-positron collider at CERN, scientists have extrapolated the value of the coupling constants up into the energy range at which unification would take place. The failure of the three curves to intersect in a single point has been interpreted by some as evidence that new physical effects, not accounted for by the so-called Standard Model, may be at work. (CERN Courier, March 1991.)