On Jun 16, 12:24*am, "Jim Hawkins" wrote:
"Mike Dworetsky" wrote in message

...





"OG" wrote in message
...

"Jim Hawkins" wrote in message
news:dNednQy4CJfjqcjVnZ2dneKdnZydnZ2d@supernews. com...
If there were another planet, same mass as Earth and in the same orbit
but
at the precise opposite orbital position, we would presumably never see
it
because it would always be eclipsed by the sun.
Is there any way we can be sure that there isn't such a planet?

Jim Hawkins

It would be detectable due to its perturbation of the orbits of other
solar system objects.

Yes.

And perturbations by other planets would move it out from behind the sun
where it could be seen, and from time to time it would approach the
longitude of the Earth, when all hell would break loose due to tides while
the two passed each other. *The situation would resemble the co-orbital
moons of Saturn, Janus and Epimetheus.

Even the "presumably" of the OP is wrong. *At total eclipses of the Sun,
any Earth-similar planet on the opposite side of the Sun would be directly
visible more times than not. *The Earth's orbit isn't circular and
Kepler's second law would apply, so it would not always be exactly 180 deg
different in true anomaly.

Objects like Cruithne (which has the same period as Earth) could not exist
in a captured orbit if an Earth-like planet had a similar orbit. *This
goes back to OG's point, of course.

--
Mike Dworetsky

Thanks for the explanations, Mike and OG (and thanks to A N Other who sent
me an email on the same lines).

Jim Hawkins- Hide quoted text -

- Show quoted text -



The only thing that is perturbed are these guys and their thinking for
while they talk of an elliptical orbital geometry,the framework they
use is circular -

http://upload.wikimedia.org/wikipedi...3%A9reo.en.png

Your hypothetical question aside,the ability to believe that you can
reference axial rotation off celestial sphere geometry while
referencing orbital motion off the central Sun is truly a remarkable
belief in a simpleminded sort of way,the genuine belief among
empiricists that they actually can justify axial rotation in 23 hours
56 minutes 04 seconds because they can see a star returning back to a
observed location in that time.Aaarrr, Jim lad,were it only that
simple.

If the anonymous science entity thinks it can script whatever
explanation it wants and sell it to the general population then they
should learn that the trick of obfuscation,no matter how elaborate and
supported,does not work. In this respect,there is some joy this week
in seeing ordinary people reject a European treaty even though the
treaty had the backing of every organisation with power,a re-packaged
treaty that was given a new name and wrapped up in legalise in order
to bludgeon people into acceptance,the same tactic used in a section
of science day in and day out.Only this time it failed.

Given a chance,people do find their voice,the dismay of politicians in
seeing that people will not follow something because they are told it
is good for them is outweighed by the sense that originality and the
tendency to fight against mediocrity and bureocracy is not quite dead
yet.Oh that it existed in these forums where even those who towed an
anonymous empirical line realised the damage that was and is still
being done using terrestrial/celestial phenomena.