Abstract:
Apparent periodicity was observed in the mass extinction event for the past few hundred million years. Previous investigations suggested the observed period to be somewhat lower than the calculated period of oscillation of the Sun about the galactic plane. Our knowlege of the structure and surface density of the Milky Way has changed radically over the past decade. The present investigation aims to calculate the time period of the Sun's oscillation about the galactic plane using the latest model of the vertical structure of the disc in the solar neighborhood and to see if it matches the extinction periodicity, which it does indeed, but with a quarter, not one-half, of the period of oscillation
