Quote:
Originally Posted by Piers
As to the superficially regular pattern of extinctions, well the dates of the mass extinctions are hardly new - (I suspect most students of evolutions over the last fifty have spotted the pattern). Its probably just coincidence, however there could be some other explanation. *danger wild unsupported speculation* Maybe the earth’s orbit ‘regularly’ passes into the same plain as a group of comets increasing the chance of impact, or maybe there is some geological cycle.
David Raup and Jack Sepkoski published a paper in the Proceedings of the National Academy of Sciences in February, 1984 demonstrating a 26-million-year periodicity in mass extinctions. This led to the question, why would these extinctions be regular and what caused them? The answer came from astrophysicists who postulated (among other theories) a "Death Star" companion to the sun, dubbed Nemesis. This star would periodically come close to the sun, disturbing the Oort Cloud of comets, sending some of them to rain down on Earth, thus killing substantial amounts of life on earth.
Unfortunately no one has ever seen this Nemesis star, which is not due to return for another 13 million years or so. In fact no one has seen the Oort Cloud either, although I understand most astrophysicists believe it is there.
Additionally Raup and Sepkoski's work has been questioned. This new work may be better informed.