Galactic Dark Matter and Terrestrial Periodicities

Abstract

Abstract : Analysis of recent geological databases reveals the presence of a ^26.5 Myr periodicity in the terrestrial record of the last ^200 Myr. The same periodicity is found to be present, at a high confidence level, in the record of impact cratering on Earth. It thus appears that global disturbances are modulated or caused largely by exogenous forcing. The likely source is a periodic comet influx caused by Oort cloud disturbance as the Sun oscillates vertically through the Galactic disc. The Earth may thus be regarded as a probe of the disc environment; and to account for the periodicity, the Galactic disc is required to have a substantial dark matter component (^approx .15 molar mass/cu pc). The purpose of this paper is to review the relevant observational framework, and to describe the basic astro- and geo-physical processes which now seem to underpin evolution on Earth. The resulting current hazard to Earth, amounting to a more substantial input and explosion megatonnage in toto, is both more complex and more profound.