Re: Does the earth wobble?

[Tompaleo@xxxxxxx]

>>If the Eart wobbles, it is most likely 
>>that it's the result of a huge meteor impact.

>Now this I really doubt. If I remember my physics, you would need a >huge
>meteor travelling incredibly fast to have even a slight effect on the
>trajectory of the Earth. On the other hand, it mightn't take so much >to add
>a little to the spin, like putting spin on a cue-ball. Anyone like to try
>out some figures to see if its plausible?

The earths wobble on  a ~20Ky is the result of the distribution of mass
throughout the sphere of the globe. Since these distributions can be changed
by plate tectonics, wind, water, volcanism and the motion of the earths inner
core the tidal forces between the earth and moon are changed. Think of a
spinning top or how a gyroscope spins  and then change the distributuin of
mass (ie forces). The spin axis of the top or planet will be an equilibrium
position until a net force changes its motion again. BTW, the polar axis of
the planet Uranus is tilted ~87 degrees toward the ecliptic. So when you are
looking at the planet through a telescope you are actually seeing it's south
pole, the northern hemisphere is in perpetual darkness! The latest theory as
to why this is so is that a large asteroid or planetoid struck the planet
eons ago. Just look at the multiple impact of SL-9 on Jupiter recently to see
that the scenario is quite likely. Another planet, Mars, has a similar axial
tilt ~25 degrees and it's day is slightly longer than earths  at 24h 39m 35s
compared to 23h 57m and has similarly longer Milankovitch cycles.



>The earth wouldn't move fast enough or far enough to kill off the 
>dinos, or we'd at least have a killer world record crater. So, in a 
>nutshell, I have a lot of doubt that axial tilt had anything to do with 
>the dinos.

Most definitely true. And since we have paleomagnetic records going to ~165
Ma, long before the K-T impact,  precession can be ruled out as a cause for
extinction.

                                     Regards,
                                     Thomas R. Lipka 
                                     Paleontological/Geological Studies