MEASURING GRAVITY GRADIENTS WITH ATOM INTERFEROMETRY. Splitting an atom into two wave packets and then recombining them will produce an interference pattern that depends on any forces that are present, including gravity. By putting two such atom interfermometers together, Mark Kasevich (203-432-3826, mark.kasevich@yale.edu) and his Yale colleagues have made a highly sensitive gradiometer that will soon be able to detect changes in gravity as small as 10^-10 g over a distance of 1 meter, as good as any technique now available, and likely to get even better after more development. Because the test objects whose acceleration is being measured are individual atoms rather than bulk objects and because the readout is based on stable laser beams, systematic uncertainties are eliminated or greatly reduced. Also, the device is immune to vibrations incurred on moving platforms, which should make it valuable for pending gradiometer applications such as covert navigation, underground structure detection, oil exploration, and geodesy, as well as for fundamental studies of general relativity. (Snadden et al., Physical Review Letters, 3 August 1998.)