A low-threshold test ban is feasible

At present, nuclear explosions are limited by treaty to underground testing with yields of no more than 150 kilotons, and recently there have been renewed calls for further test restrictions. As part of these discussions, the U.S. Congress is considering bills that would legislate new limits to testing,whereas the Reagan Administration opposes such constraints. The editors of Science have asked two groups of participants in the debate to present their arguments for or against new limits to testing. Feiveson, Paine, and von Hippel argue for a treaty of indefinite duration between the United States and the Soviet Union, which includes the following provisions: (i) a ban on all testing outside a desiqnated site having known seismic properties; (ii)verification by means of on-site inspection and in-country seismic monitoring; (iii) unlimited testing below 1 kiloton at the special site; and (iv) an average of one test per year with a yield of up to 15 kilotons for ensuring reliability of the nuclear stockpile. MiUer, Brown, and Nordyke argue that a lowering of the present 150-kiloton threshold would be undesirable, and that new test bans would divert attention from a comprehensive approach to negotiated reductions in the nuclear and conventional arsenals of the United States and the Soviet Union.     

Borehole measurement of the newtonian gravitational constant

It has been reported that the geophysically determined Newtonian gravitational constant is consistently larger than the laboratory value by 1 to 2% on the basis of gravity measurements in Australian mines. This discrepancy may have strong implications for the physics of gravitation. To test whether similar results can be observed in a different geological environment, gravity measurements in a Michigan borehole have been examined. Although these results cannot be taken as conclusive, owing to the large uncertainties involved in mass determination on a geophysical scale, these measurements are generally consistent with those of the Australian experiment.