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4/20/2006 Physics Colloquium: Richard A. Muller
Physics Colloquium Series at
MIT
4/20/2006
Richard A. Muller, University of California - Berkeley
Cycles in Fossil Diversity
We have recently analyzed the most complete record of marine animal
fossils ever compiled, the "Compendium" of Jack Sepkoski, which
lists all known fossil marine animal genera back 542 million years.
When the fossil diversity (number of distinct genera) is plotted, it
shows a very strong 62 Myr cycle. The cycle is particularly evident
in the species that endured for relatively short times. We examined
many possible causes for this cycle, including movement of the Earth
through the Galaxy, volcanic eruptions from the core of the Earth,
variations in the energy output of the Sun, comet bombardments from solar
system perturbations, an intrinsic biological cycle, and more. No
known mechanism accounts for the cycles. There is one other strong
cycle in the data, with period 140 Myr. This matches a previously
known climate cycle, and may be due to the passage of the Earth through
the arms of our galaxy. Our initial results were published in
Nature, vol 434, 208-210, 10 March 2005. See also
www.muller.lbl.gov.
Time: 4:15pm
Place: Room 10-250
Refreshments will be served in the Physics Undergraduate Lounge (8-329)
at 3:45pm
For a complete list of upcoming colloquia, please visit the Physics
website:
http://web.mit.edu/physics/newsandevents/physics_colloquia_sched_spring_06.html
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