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Re: Does the earth wobble?



> Now, I have a question. How is "wobble" measured? I expect that it is so
> slight that it is very hard to detect.
Actually, using laser technology, we can measure "wobble" in the Earth 
and the moon (which probably wobbles more than Earth) using mirrors. I 
think the equipment was set up during the Apollo missions. The equipment 
(I don't remember the figure exactly) is supposed to have an accuracy of 
about 5 cm.

> The figure of 20,000 years for the cycle has been bandied about. Is it
> possible that this is simply a "harmonic" of a much longer cycle, perhaps
> lasting millions of years and going through a larger angle? Obviously a
> longer cycle would be harder to detect.
I don't believe the cycles are that long. Otherwise, we wouldn't be able 
to measure the wobble very well. 

> I don't think wobble is likely to be a cause of extinction. My point is that
> if the tilt of the Earth was different during the mesozoic it would have a
> huge effect on the climate, particularly near the poles. If the earth had no
> tilt there would be no seasons, or if the angle was smaller the effect of
> seasons would be much less. We know the earth was much warmer then, and this
> could offer a partial explanation why.
I'm neither an expert in astrophysics or paleontology, but I'm quite 
interested in both, and I remember a little more about astrophysics than 
paleontology. So I'll give my idea: I don't think the Earth is tilted any 
more or less than is has been, or at least not to a noticeable effect. 
There are so many factors that affect global climate, it's a real shot in 
the dark to pin it down to one. If the Eart wobbles, it is most likely 
that it's the result of a huge meteor impact. Now I guess it gets down to 
your definition of "wobbling". I'm assuming you mean the Earth in some 
simple harmonic motion going back and forth, relative to it's orbit or 
some other point of reference. If the meteorite was of the correct 
trajectory, it could turn the Earth, (that would be one hell of a bang) on 
the north-to-south axis, but that wouldn't be a wobble so much as free 
rotation. In that case, the Earth would continue rotating, and would 
continue for millions of years right up to present day. If the effect of 
the axial tilt was enough to kill off the dinos, then it would at least be 
measureable now, if not kill us off too. Back to the SHM. If that were 
the case, then the average global climate would most likely still be in 
check. 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.

> On the other hand, if I am flogging a dead horse, please let me know.
I welcome this discussion. It's the first where I can actually contribute 
something worthwhile (I hope :) )

Alex Hertzog