Name: Prairie View, Ken E Hawley, and Andy Beaucage
Why is Uranus tipped on its side?
This is one of the great unanswered questions about our solar system. Some
astronomers think that this is just the way Uranus developed, but that does
not seem to me to be consistent with how most scientists think that the
solar system developed. The other widely-held belief is that the tipping is
the result of a collision between Uranus and some other body long ago.
There are some problems with this explanation too: if such a collision took
place, why is Uranus' orbit so nearly circular (just like the orbits of most
of the other planets, which presumably did not suffer the same sort of
collision)? Similarly, assuming Uranus' moons formed before the collision,
why are their orbits also nearly circular? They orbit Uranus in essentially
the same plane as Uranus' equator. As you can see, we do not have to go to
the ends of the universe to find puzzling questions.
This is one of the big mysteries in the solar system. It is probably
because Uranus was hit by something really big in its early history,
knocking it off it is old rotational axis (which would be expected to be in
the same plane as the orbit like most of the other planets).
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Update: June 2012