QUOTE (helvick @ Oct 14 2006, 04:17 AM)
That was my thinking too.
To nudge this slightly back on topic. There are plenty of theories out there (Martian polar wander, the long term stability of the earth's inclination resulting from the moon etc) that seem to imply that the inclination of the planets should be fairly widely distrubuted. In that case no really odd mechanics is required to explain the Uranian tilt. However if it really is that "simple" then how come it's the only really extreme one?
We can probably exclude Mercury and Venus as being solar-locked, and we can perhaps exclude Earth on the anthropic principle (would we be here as an advanced species to discuss the issue if Earth had Uranus's inclination?).
That leaves us with Mars and four giants, plus choose-as-you-like for other worthy bodies to include in the discussion. Pluto is tidally locked to its satellite, which probably excludes that one from consideration (Mars and the giants are NOT locked to their satellites, to say the least). Eris is unknown.
Jupiter and Ceres are very low inclination. Earth, Mars, Saturn, and Neptune are eerily similar in their modest inclinations; Vesta is also in that general vicinity. Then Uranus is the big outlier. Mars, at least, is prone to swings over geological time. Earth and probably Saturn seem to be stabilized and I'm quite sure that the other three giants are too big/too far from anything to get tossed around.
It's important to note that this is a very small n
. You can't call any trends you spot statistically significant. I wonder if the "expected" distribution is flat or clustered in Gaussian fashion around 0. The data leads me to the wild guess that it is the latter, and it's a fluke that the "midrange" instances are clustered around 25 degrees with nothing between 6 and 21 or between 30 and 90. If one standard deviation is 30 degrees, we would expect about 2/9 to be in each of these bins: 0-10, 11-20, 21-30. The first bin got its quota and it just happened that the third bin ended up with "both" of the planets that "should have" been in the second bin, and one that "should" have been in a higher-number bin. Three little flukes. A friend of mine had a phone number with "666" in it -- things like this happen.