tt40 wrote:
Phew, I'm overwhelmed by the considerable and considered lengths that
respondents have made on this topic. (Of course it's tempting to be a
smart-alec and ask 'Yes, but why an ellipse?' as if to off-handedly
tilt at the signficance of mathematics in answering my question, but
that would lazy and disingenuous).

** To clarify, as was requested by some, the extended version of my
question is 'Why an ellipse and not a circle?' And thanks to those who
recognised this -- an imprecision on my part. **

It is a fascinating topic and I wish I understood (read 'could
configure my life so I had the time to learn') the maths.

Sorry that I've only had time to skim the thread, can't wait to read it
all in detail.

Greg.

It is no longer possible to isolate the elliptical geometry of orbital
motion as attempt to persuade people that it is a larger version of
terrestial ballistics.

For over a 100 years,geologists and climatologists have found that mid
latitude glaciation or ice ages contain the clues for a variation in
the shape of the planet's orbit from more to less elliptical.Because
the relationship between axial and orbital motion changes depending on
whether the geometry is more elliptical or less,the regretable feature
of the Newtonian scheme is that no such variation can be considered.

Newtonian physicists have axial and orbital motion sharing a common
axis when both motions are actually independent of each other -

http://www.pfm.howard.edu/astronomy/...S/AACHCIR0.JPG

Because they insist of a constant orbital displacement,if you extend
the orbital geometry to an ellipse,you will witness an assault on the
eyes for under such a justification ,the Earth would travel faster at
the aphelion !,Go ahead and try it.

The moral is don't be desperate for elliptical orbital causes and
certainly not terrestial ballistics or the silly and grandiose named
'unioversal laws of gravitation'.