[QUOTE=tony873004]
The problem with the planetary disk condensing the way it is is that orbital periods are quite slow at the distances of Uranus & Neptune, and the disk material is theorized to have been too thin at that distance that the lifetime of the solar system is not long enough to have allowed Uranus & Neptune to accrete. This suggests they formed closer to the Sun, and migrated out to their current positions.
(eddit to add end quote here)

(i havent seen anyone suggest this apart from one other person who was to put it mildly rather `strange')got any links?


In the particular case of this Nature paper, the author's concern about the planets forming in their current locations is that it doesn't explain the tilts of the gas giants, especially Uranus. If Uranus were knocked on its side by a giant collision, there's no reason to believe that the orbital planes of its moons would have enough time over the life of the solar system to catch up with the planet's equator. So he speculates that if Uranus got tipped on its side gradually over the course of hundreds of thousands of years, that the moons orbital planes would be able to keep pace with the changing orientation of Uranus' equator. Although he doesn't say so in the paper, it seems to me that unlike the impactor theory, the planatary pertubation theory would provide torque to the planes moons' orbits as well as Uranus' equator.


ummm


by exactly what mechanism would a planatary impact (changing its axis of rotatation or not) have any ef(F)ect on the moons orbits anyway??

seems like either you i or both have misunderstood him-or he really has no idea about planets,orbits or anything else to do with planetary movement or newtons `laws'

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Surely if you are going to start a conspiracy theory it is best to start with something that might have a grain of truth or reality in it. To start with the preposterous and go downhill from there is just stupid. steve(primus) (Avatar)