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Re: Missing the point of Nemesis
- To: meteorite-list@meteoritecentral.com, phil@ticetboo.demon.co.uk
- Subject: Re: Missing the point of Nemesis
- From: Louis Varricchio <varricch@postal.aero.und.edu>
- Date: Thu, 10 Jun 1999 08:51:17 -0500
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- Resent-Date: Thu, 10 Jun 1999 09:52:48 -0400 (EDT)
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What point are we really missing? There's an underlying philosophical point
I'd like to make. Personally, I am not so cock-sure about some of our
contemporary, accepted scientific
"facts"--i.e., what's beyond the orbit of Pluto? Naturally, I do NOT mean
we should consider there's a chance of discovering Planet X populated by
exotic angelic beings who look like Pamela Anderson and Fabio--mmmm... : )
After all, there are some intelligent questions challenging the actual
existence of the "Oort Cloud" itself by a few maverick astronomers. Ok,
they may be a minority, but why should that ever dismiss an open discussion?
It's bad enough many of the peer-reviewed scientific journals make many of
their contributors tow the party line on so many subjects. A geologist
friend of mine once said, "One stubborn peer reviewer can ruin your whole
day (and career)!"
I always enjoy seeing how we are so quick to accept, as fact, the
oft-repeated "truths" of our experts, especially when those who really dig
into a subject know there's a shadow of a doubt. But neat and tidy theories
are only neat and tidy when you either ignore, or reject outright, data that
doesn't fit the paradigm. I know that's not a popular position to hold in
the sciences these days; sciences that, seen from an inside vantage-point,
can border on the dogmatic.
Either way, 'rambling on' (especially about controversial, but still
intelligent and legitimate topics like lunar tektites, K-T boundary
questions, why some lunar and martian meteorites found on Earth are
"unshocked," and distant stellar companions) does make for a lively
discussion group! Now I've rambled on long enough. Thanks for the soap
box.
Louis Varricchio
Environmental Information Specialist/Research Associate
Upper Midwest Aerospace Consortium
University of North Dakota
Grand Forks, N.D. 58202-9007 U.S.A.
Telephone: 701-777-2482
E-mail (in N.D.): varricch@umac.org
E-mail (in Vt.): morbius@together.net
>>> "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.
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. If all the extinctions had the same cause - and it is by no
means clear that they did - then one possibility may be a regular influx of
comets from the Oort cloud. The Oort cloud lies at a distance of about
30,000 to 100,000 AU from the Sun. One of the ways in which the cloud could
be disturbed would be by the existence of a solar companion star - the
so-called Nemesis star. But it is dynamically difficult, if not impossible,
for such an orbit to have become established and to have lasted for the life
of the Solar System. It has nothing to do with what type of star Nemesis
is - or how many companion stars there may be - it is purely a dynamical
problem based on the distance of the Oort cloud.
Now, it has got to be said that Raup & Sepkoski's data have been subject to
much criticism from statisticians and palaeontologists alike. The geologic
record is by no means complete, and doubts have been raised about the
radiometric timescales used by the two researchers. There is also a
background 20-30 genera extinctions every million years, which serves to
complicate matters further.
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? Did the Nemesis
object drift from its unstable orbit at the time of the dinosaur extinction
thus putting an end to the cyclical nature of extinctions?
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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