Today at 02:20 AM mjiracek said this in Post #69
what about the beginnings of the earth...what do you belive on that?
It's not what we "believe", but what the
data shows.
This should prove a good resource for you to pursue:
http://www.gpc.peachnet.edu/~pgore/geology/geo102.htm
http://www.union.edu/PUBLIC/GEODEPT/COURSES/geochemistry/moon_scn.htm
"As described above, long-standing ideas about the formation of the inner planets are uniformatarian in nature. The early solar nebula was shaped like a disk and contained gas and dust. The dust gradually clumped together to make pebbles, the pebbles clumped to make boulders, the boulders clumped to form asteroid bodies, and the asteroid bodies accreted by gravity and collision to form the planets:
Dust of the early solar nebula.
A great many pebbles.
Zillions of boulders.
Trillions of asteroids.
Four inner planets. This idea holds that the planets basically formed from the accumulation of a "rain" of fairly small boulder to asteroid size fragments. Recent computer models and other evidence suggest a somewhat different course of events. The beginning is the same, with tiny particles gradually clumping together to form larger particles. The difference is that, as the growth of the larger bodies is primarily by the collision of other large bodies:
Dust of the early solar nebula.
A great many pebbles.
Zillions of boulders.
Trillions of asteroids.
Thousands of planetesimals.
Dozens of protoplanets.
Four inner planets. This idea holds that the later accretion events in the formation of the inner planets involved increasingly large collisions, finally involving mammoth collisions of planet-sized bodies. The large, random collisions involved in the last stages of planetary accretion can explain many of the inner planet anomalies pointed out above:
Mercury may have its proportionally large core because half of its mantle may have been blown away by one or more giant impacts. However, where the silicate debris went is a problem for this concept.
Venus may have its slow, retrograde spin because its last big collision may have, by chance, almost eliminated Venus's spin.
Earth's moon and the large angular momentum of the Earth-Moon system may have been caused by an oblique giant impact on the proto-Earth. This impact, by chance, put enough material into orbit to crate our moon.
Although Mars has no dramatic anomalies, the geology of Mars is asymmetric, which may have been instigated by a large late collision. References and further reading
Ahrens, T.J., 1994, The origin of the Earth. Physics Today, August, p. 38-45.
Meyer, Charles, 1987, The Lunar Petrographic Thin Section Set. NASA, Curatorial Branch Publication No. 76, Lyndon B. Johnson Space Center, Houston, Texas, 77058, 61 p.
Nozette, Stuart, et al., 1994, The Clementine mission to the Moon: scientific overview. Science, v. 166, p. 1835-1839. Also see several related articles in the same issue.
Stevenson, D.J., 1987, Origin of the Moon-the collision hypothesis. P. 271-315, in Wetherill, G.W., editor, Annual Review of Earth and Planetary Sciences, v. 15, Annual Reviews, Inc., Palo Alto, California, 614 p.
Taylor, S.R., 1987, The origin of the Moon. American Scientist, v..75, p. 468-477.
Taylor, S.R., 1994, The scientific legacy of Apollo. Scientific American, v. 271, no. 1, p, 40-47. Also see responses to this article in: Letters, A misbegotten Moon, Scientific American, v. 271, no. 6, p. 8.
Warren, P.H., 1985, The magma ocean concept and lunar evolution. P. 201-240, in Wetherill, G.W., editor, Annual Review of Earth and Planetary Sciences, v. 13, Annual Reviews, Inc., Palo Alto, California, 443 p."