Number 105 (Story #2), December 4, 1992 by Phillip F. Schewe and Ben Stein LUNAR TIDAL EFFECTS are the main cause of error in determining the mass of the Z boson. Scientists at the CERN laboratory in Geneva, Switzerland, with help from workers at SLAC and the University of Lausanne, have found that the Moon's gravitational pull warps the LEP (Large Electron Positron) collider by as much as a millimeter (out of a total circumference of 27 km). This blurs the Z mass estimates by about 10 MeV. Hereafter, calibrations of the beam energy will take into account the phase of the Moon. (CERN press release, 23 Nov. 1992.)