Re: Solar System's rotation

[Larry Woolf <Larry.Woolf@GAT.COM>]

The best estimate is that the earth formed about 4.6 billion years ago, not
12 billion.   According to a recent article in the Sep-Oct 2001 issue of
American Scientist (pages 432-442), the protoearth accretion was 99%
complete 40 million years after "the settling of dust in the accretionary
disk of the protosolar system."

See Cameron, A. G.W. 1978. Solar accretion disk and planetary formation.
In Origin of the Solar System, ed. S. F. Dermott, pp. 49-74. New York:
Wiley.

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At 8:10 PM -0700 9/10/2001, Paul O. Johnson wrote:
 But itdid not touch on the subject that I have wondered about for many years
> -- how long the earth required to grow to its present size.
>
> We often read that the earth was formed 12 billion years ago. But did
> that formation extend over a million years, or longer, or shorter? Do
> the current models of planetary formation give a time for this?

Dr. Lawrence D. Woolf; General Atomics, 3550 General Atomics Court, Mail
Stop 15-242, San Diego, CA 92121