From: Robert J. Bradbury (bradbury@www.aeiveos.com)
Date: Tue Dec 21 1999 - 11:11:23 MST
On Mon, 20 Dec 1999, Eliezer S. Yudkowsky wrote:
>
> Now for a different stumper I got hit with (once; after that I looked it
> up). How do we *know* the Earth is 4.5 billion years old?
Oooh, oooh, oooh, a question I can answer...
This is derived from the ratios of various radioactive elements and
their decay products in crystallized minerals in meteors, the Earth
and the moon using highly accurate mass spectrometry methods. We know
that some elements can only be produced in supernovas. Those elements
get expelled into the clouds that collapse into nebulas and then condense
into the star(s) and/or planet(s). By looking at spectra from the sun
we can determine the relative abundances of these elements in the solar
nebula. By looking at the abundances in rock samples we can determine
the relative times of crystalization.
For a pretty in-depth discussion see:
http://corona.eps.pitt.edu/www_GPS/courses/GEO0840/118.html
http://www.owlnet.rice.edu/~geol108/Test1QandA.html
If you want some good examples of psuedo-science and creationist
babble, try:
http://www.panama.gulf.net/~godsword/old.htm
http://www.forerunner.com/forerunner/X0741_Origin_of_the_Univer.html
http://dialspace.dial.pipex.com/town/avenue/xlm75/netchristian/the.htm
One of the things that was fascinating in looking for pages about
this is the observation that there seem to be many more pages
of the 2nd group than the 1st group on the net!!
Sigh.
Robert
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