> As it turns out the ecliptic may be the 'real nemesis,' responsible for > past mass extinctions on earth. > > The ecliptic plane is canted wrt the galactic plane, and the result is > that the sun traces what is in effect a circumferential sine wave, such > that it swings sequentially closer, and then furhter away from the the > MW plane
No Jones, the 62My period "vertical" oscillation superimposed on the "horizontal" circular orbit of the sun round the galactic center has nothing to do with the inclination of the solar system plane wrt the galactic plane. It is a purely gravitational effect due to the galactic plane being denser. The "real nemesis" is more likely to be the galactic plane itself, around which our solar system is more likely to undergo collisions. Such collisions explain why rotating clouds of matter always end up as planes BTW. Actually I believe we are still in the danger zone presently, having crossed the plane only 1My ago or so. It seems to me this is in favor of using solar sail reflectors to mitigate global warming BTW: such reflectors could also be used occasionally to deviate from very far away any asteroids detected to be on collision course, using photon pressure as was discussed here some time ago. Michel ----- Original Message ----- From: "Jones Beene" <[EMAIL PROTECTED]> To: "vortex" <[email protected]> Sent: Sunday, May 06, 2007 5:04 AM Subject: [Vo]:The Ecliptic and Mass Extinctions > Once upon a time ... it was believed that our sun was paired with a > hypothetical companion star, 'Nemesis' which might orbit at a distance > of a light year or so. Nemesis was introduced to explain an apparent > periodicity in the occurrence of mass extinctions of around 65 million > years. In the past 26 years of intense searching, Nemesis was never > found - and it should be relatively easy to find if it were there. In > the mean time, we have discovered dozens of planets orbiting stars at > similar distances, for instance. This companion star, if it existed, > would need to be much larger than any planet. ERGO, it is most likely > that no such companion star exists. > > Reference was recently made on Vo to the 'ecliptic,' which is the > apparent path that the Sun traces out along the sky, and the imaginary > disk of the ecliptic which is enclosed within the larger Milky Way disk. > As it turns out the ecliptic may be the 'real nemesis,' responsible for > past mass extinctions on earth. > > The ecliptic plane is canted wrt the galactic plane, and the result is > that the sun traces what is in effect a circumferential sine wave, such > that it swings sequentially closer, and then furhter away from the the > MW plane and the protection (from extremely strong comic rays) which is > afforded within the galactic plane, but not when we swing outside pf it. > > The cycle of this swing is around 63 million years, which is a close fit > with the cycle of mass extinctions. > > There is an short article in 'Science News' two weeks ago: > > http://www.sciencenews.org/articles/20070421/fob3ref.asp > > "Northern Exposure: The inhospitable side of the galaxy?" by Davide > Castelvecchi > > Executive Summary: Our solar system's periodic motion from one side of > the galaxy to the other could expose life on Earth to massive amounts of > cosmic rays and cause recurring, catastrophic mass extinctions. > > References: > > Medvedev, M.V., and A.L. Melott. In press. Do extragalactic cosmic rays > induce cycles in fossil diversity? Astrophysical Journal Abstract and > preprint available at http://arxiv.org/abs/astro-ph/0602092. > > Rohde, R.A., and R.A. Muller 2005. Cycles in fossil diversity. Nature > 434(March 10):208-210. Abstract available at > http://dx.doi.org/10.1038/nature03339. > > Further Readings: > > Monastersky, R. 1997. The big chill. Science News 152(Oct. 4):220-222. > Available at http://www.sciencenews.org/pages/pdfs/ > data/1997/152-14/15214-15.pdf. > >
