Number 169 (Story #1), March 17, 1994 by Phillip F. Schewe and Ben Stein LIMITS ON THE FLUX OF MAGNETIC MONOPOLES streaming through the solar system can be determined from the apparent lack of proton decays. Magnetic monopoles have never been unambiguously observed, but some theories suggest that if they exist they might catalyze proton decays. Working backwards, scientists at the IBM proton-decay detector in Ohio use their measured lack of proton-decay events to calculate monopole flux limits for a variety of hypothetical monopole velocities. For a velocity of 0.001 c and a proton-monopole cross section of 10**-24 cm**2, they derive a monopole flux limit of 2.7x10**-15 cm**-2 sr**-1 sec**-1. (R. Becker-Szendy et al., Physical Review D, 1 Mar.)