On Tue, 2010-01-05 at 17:54 -0800, Alastair wrote:
> OTOH, we are talking about asteroids that start out close to Jupiter.
> As the major axis of the asteroid was extended, the asteroid might
> have reached Jupiter before the minor axis was small enough for it to
> reach Venus. In that case, would Jupiter be the frontstop? It may be
> easy to check with the right data, whether the asteroid could mmet
> earth but not Venus before reaching Jupiter. We know roughly the
> initial solar orbits of the icy asteroids - greater than 3 AU to
> Jupiter's 5 AU and Venus at 0.723 AU.
This is a matter of gravity(1). The gravity of Jupiter will always be
perturbing the orbits of everything else in the solar system. To learn
more, I would suggest downloading a gravity simulator and try some
experiments with asteroids with orbits like these.
Intuition doesn't work well on orbital physics. For example: Going
faster makes your orbit slower. Slowing down usually increases your
average velocity. Having an orbit that exactly intercepts another body's
orbit means that there may not be a collision (unless both bodies are
small enough, or the relative velocity is high enough, or some special
cases).
It has been a long time since I spent a lot of time with an orbital
simulator, and the only one I could recommend first hand you would
probably have a lot of trouble getting to work on a modern computer.
However, Google searching for "gravity simulator" gives this as the
first hit:
http://www.orbitsimulator.com/
I have not tried it, but it looks both very user friendly and useful.
Some very nice examples are included.
If you want Linux or MacOSX you might try:
http://gravit.slowchop.com/
If you want something research grade, but expect to spend a lot more
time learning about the subject, this (and some of the others referenced
from this) looks hopeful:
http://bima.astro.umd.edu/nemo/
A day or a week or so playing with orbits should help anyone to
understand this subject better.
(1) No pun intended.
--
Phil Hays <[email protected]>
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