Earth2 ?

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

"Jim Hawkins" wrote in message
m...
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.

"OG" wrote in message
...

"Jim Hawkins" wrote in message
m...
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

(Remove pants sp*mbl*ck to reply)

"Mike Dworetsky" wrote in message
...
"OG" wrote in message
...

"Jim Hawkins" wrote in message
m...
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

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.

On 17 Jun, 05:16, oriel36 wrote:
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.


Of course it could be that you are correct and thousands of
professional and amateur astronomers are wrong.

However until you can be bothered to publish a detailed explanation of
your theories in a peer reviewed journal I am inclined to believe the
majority.

On Jun 16, 10:16 pm, oriel36 wrote:

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

Nah. Celestial sphere geometry is just a convenience for knowing where
to point things. If you're going to do any calculating, there's only
one geometry to use - Cartesian coordinates, x, y, and z.

Unless, of course, general relativistic effects are so strong that
they're nonlinear; then there's nothing for it but to go whole hog
with tensor calculus. Thankfully, while general relativistic effects
are strong enough to be *detectable* in the precession of Mercury,
they're still nowhere near strong enough to require THAT. (Depending
on the precision you need, of course.)

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.

Well, we have to start with the simple stuff.

Aaarrr, Jim lad, were it only that
simple.

Celestial motions *are* a whole lot simpler if you can untangle them,
and look at one motion at a time. Using the distant stars as an
approximation to a stationary coordinate system _is_ a great way to
get started. If you don't like it - that's your problem, not ours, I'm
afraid.

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,

Here's something I agree with you about. Most Europeans don't want a
less-responsive European Parliament and are happy with their own
national governments. However, with a free trade area, a common
currency - the Euro - _is_ needed to gain the full benefits, so a case
can be made for some additional integration over and above that of the
original European Economic Community.

And from what I've heard about the issue, you are also right that the
new treaty is much the same as the old one that was rejected in
referendums despite it being claimed that it is different enough so
that no referendums are appropriate this time.

But modern science is hard to understand *not* because scientists have
dressed it up in jargon, but because it genuinely *depends* on fancy
mathematics.

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.

I can't even guess what damage you are referring to that we were aware
of. I wish I could usefully communicate with you to get information
about where we're supposed to be wrong that I could get a grip on.

John Savard

In uk.sci.astronomy message dNednQy4CJfjqcjVnZ2dneKdnZydnZ2d@supernews.
com, Sun, 15 Jun 2008 16:25:46, Jim Hawkins
posted:
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?


Even if the Universe consisted solely of the Sun, Earth in circular
orbit, and counter-Earth, the system would not be dynamically stable; it
would be like an infinitely-sharp pencil balanced on its point in an
infinitely-hard flat surface. That conclusion is independent of the
mass of counter-Earth.

Plus what others have said.

The argument that the Earth's orbit is not circular, and hence its
angular velocity is not constant, implies that a body in the same
orbital path would not remain diametrically opposite. But a body in an
orbit of the same shape but "pointing" in the opposite direction to
ours, if initially behind the Sun, would remain so until the effects of
perturbations and instability accrued. That's analogous to L4 & L5
still working for elliptical orbits.

--
(c) John Stockton, nr London, UK. Turnpike v6.05 MIME.
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
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