Re: ZetaTalk and Spaceguard UK

Greg Neill wrote:
> If you would take the time to read a book on astrodynamics,
> you would know that there is of course a theory of orbital
> motion. It is derived from Newton's law of gravitation, and
> renders orbits that behave just as we see them, including the
> various pertubations. ... Planets trade energy by way of Newton's
> force law.  ...  Gain a little, and you move away from the Sun.

Fine.  Explain why Pluto moves AWAY from the Sun, after having been
perturbed inward.  Explain how gravity can be a push-away.  What PULLS
or PUSHES Pluto away?  How long does it take to return to its orbit?
And please don't tell me something on the other side of the Sun pushes
Pluto AWAY from the Sun, due to some center of the solar system thing.
This is a drama between Pluto and the Sun, and anything on the other
side of the Sun would only INCREASE the gravity pull TOWARD the Sun on
Pluto.

Bill Nelson wrote:
> Why would we want to calculate "gravitational forces" in the
> same way. We are not interested in the causes of the forces,
> only the magnitudes and directions of the forces.
>
> So, we use one equation that accounts for the gravitational
> attraction between the Earth and the Moon. We use a different
> equation to account for the centripital force (due to momentum)
> of the Moon.

The force of gravity is what it is EXCEPT in the Centrifugal Force
equation.  Then we use a lesser force as otherwise the math does not
work.  The force of gravity is what it is EXCEPT when planets return to
their orbits after having been perturbed inward toward the Sun.  Then we
use a mytical barycenter concept as otherwise the math does not work.
You can't put your concepts together!  Your math only works when you
keep things apart and have convenient amnesia!

Daivd Tholen wrote:
>>> Perturbations can work both ways.  Six years later, Jupiter
>>> will be on the other side of the Sun, causing the barycenter
>>> to shift, thus the heliocentric osculating orbit for Pluto
>>> will now be different. It's called indirect perturbations.
>
>> Pluto is the OUTERMOST Planet ... How can Jupiter,
>> anywhere, do a push-away from the Sun to Pluto!
>> You're saying the Sun moves away from Pluto, and Pluto
>> just stays where it is, not noticing?
>
> That's not what I'm saying at all.  I'm saying that the
> osculating orbit for Pluto changes as a result.