The Shiva Hypothesis (fwd)

[Dominik Wujastyk]

INDOLOGY members of long standing will remember an unexpected posting to
the group in January 1995 which was sent from McMurdo Station in
Antarctica -- surely the most remote imaginable location for indological
reflection.

The author of that posting, Rolf Sinclair, now writes to us from the more
temperate location outside Washington D.C.

-- Dominik Wujastyk

---------- Forwarded message ----------
Date: Tue, 3 Mar 1998 19:26:23 -0500
From: Rolf Sinclair/NSF Physics Division <rsinclai at nsf.gov>
Subject: Re: fwd: The Shiva Hypothesis


Dear Colleagues -- I would like to describe some recent work in astronomy
that may interest you because it has led to the naming of an astronomical
theory as the "Shiva Hypothesis". This theory describes an astronomical
model for the seemingly periodic mass extinctions of species on Earth, and
a subsequent "starting over" of the biological record. I would be grateful
for your comments on the choice of "Shiva" to identify the hypothesis. I am
not on this list, so please send any comments to me as well as to the list.

The basic idea is this: the Sun is one of a very large number of stars that
make up our galaxy -- the galaxy that is spread across the sky as the
"Milky Way". (Outside our own galaxy we glimpse many other such collections
of stars -- other galaxies -- making up the universe we observe. A good
description is in the Encyclopedia Britannica, under "Galaxies".) Our own
galaxy is disk-shaped and rotates like a giant pinwheel, with the Sun and
the other stars joining in this rotation. As the Sun turns with the galaxy
(taking some 220 million years for each rotation), it periodically
oscillates back and forth through the plane of the galaxy -- an
"up-and-down motion", perpendicular to the rotation, on a time scale of 26
to 30 million years. The planets (including the Earth) travel along with
the Sun, like a brood of chicks with their mother hen. Each time the Sun
(and of course the Earth) crosses the higher-density central plane of the
Galaxy, it periodically encounters greatly increased interactions with
other stars and with the small-scale interstellar debris, a lot of which we
term comets.

Michael Rampino (New York University), the author of recent papers on this
subject(*), then asks: Could recurrent waves of impact by comets be
responsible for the recurrent mass extinctions of species seen in the
geologic record over many millions of years ?  A few years ago such a
suggestion would have seemed far-fetched, but recent evidence is converging
on the conclusion that mass extinctions coincide with comet or asteroid
impacts, and that periodic comet showers, triggered by the Solar System's
motions through the Milky Way Galaxy may provide a general theory to
explain impact-related mass extinctions. The cyclic extinctions are
followed by explosive evolution of the surviving species that re-filled the
many life niches emptied by the global catastrophe, so he has named this
idea the "Shiva Hypothesis", after the Hindu deity of cyclic destruction
and renewal.

Like Shiva, the Hindu Destroyer/Creator, the cyclic impacts bring an end to
one world, and allow the beginning of a new one. For example, it is now
well established that an impact 65 million years ago ended the Mesozoic
world, populated by giant dinosaurs and flying reptiles, and gave way to
the modern world of mammals and birds.

(*) A short version of Rampino's paper is at
http://www.giss.nasa.gov/gpol/abstracts/96.RampinoHaggerty2.abs.html. A
popular version is in: The Planetary Report, Vol. 18, No. 1, p. 6-11
(1998), and a longer, technical version in: Earth, Moon and Planets, v. 72,
p. 441-460 (1996). An earlier paper is: "Shiva versus Gaia: Cosmic Effects
on the Long-Term Evolution of the Biosphere": in "Scientists on Gaia", ed.
S.H. Schneider and P. Boston, MIT press, Cambridge Mass, p. 382-391 (1991).

Rolf Sinclair
Division of Physics
National Science Foundation
rsinclai at nsf.gov