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Re:Nemesis - No point to miss
- To: meteorite-list@meteoritecentral.com
- Subject: Re:Nemesis - No point to miss
- From: "E.P. Grondine" <epgrondine@yahoo.com>
- Date: Mon, 14 Jun 1999 14:53:58 -0700 (PDT)
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- Resent-Date: Mon, 14 Jun 1999 17:54:52 -0400 (EDT)
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Hello Phil and all -
> >>> "Phil Bagnall" <phil@ticetboo.demon.co.uk> 06/10
> 4:33 AM >>>
> It is evident from the postings to this list that
> some people are missing
> the point of the Nemesis hypothesis. There are
> people rambling on about
> brown dwarfs and multi-sun systems, both of which
> are totally irrelevant.
Yes. A better explanation for the periodicity in
extinctions is Clube and Napier's hypothesis that our
Solar Sytem passes through the plane of our galaxy the
Milky Way, and that this dislodges POTENTIAL impactors
from the Oort Cloud. More...
> The problem is that Raup and Sepkoski claim that
> mass extinctions are
> cyclical and that, at least since the Permian, the
> period has been about 26
> million years.
The ABOUT part is important here - not only are
geological dating mechanisms not exact, there is also
the chaotic factor - while the dislodgements may take
place with a rough perioldicity, since the impactors
orbits are random, impacts will occur at varying times
afterwards. There are other planets and moons for
the dislodged objects to collide with besides the
Earth, so only a rough periodicity should be observed,
which is pretty much what happened. More...
>snip<
> If anyone seriously wishes to tackle this problem
> then perhaps the approach
> they should take is to look at the history since the
> dinosaur extinction of
> 65 mya. If R&S are correct, then there should have
> been mass extinctions 39
> mya and 13 mya. Where is the evidence for these
> extinctions?
It stries me that the date for the Chesapeake Bay
impact event fell roughly close to 39 mya, and I also
seem to remember a large change in mammal types about
them.
As for the lack of a 13 mya event, it's pretty clear
we would not be here now if one had occured. In the
past there were also a couple of "missing"
extinctions. Maybe these hit another planet as well.
EP
> A couple of good starting points are the books by
> Clube and, if you have an
> awful lot of time on your hands, by Sharpton and
> Ward. There have been
> numerous other books and papers of this subject but
> the three I have listed
> lay the foundations for research.
>
> References:
>
> Clube, S.V.M. (Ed.) 1989 Catastrophes and Evolution:
> Astronomical
> Foundations. Cambridge University Press
>
> Raup, D.M. & Sepkoski,J.J. 1984 Periodicity of
> extinctions in the geologic
> past. Proceedings of the National Academy of
> Sciences, 81, 801-815
>
> Sharpton, V.L. & Ward, P.D. (Ed.) 1990 Global
> Catastrophes in Earth History.
> Geological Society of America Special Paper 247.
>
> Phil Bagnall
> www.ticetboo.demon.co.uk
>
>
>
>
>
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