[wolfekeeper]

It would have been ridiculously easy to spot, the orbit of Mars would have been very significantly affected by another planet, at least if it was anything like a similar size to the Earth. The discrepancies would have stuck out like a sore thumb, because Mars spends half its time the other side of the Sun from us and any orbital simulations would have diverged far too quickly from reality.

I mean it's entirely possible there's an asteroid over there right now in a horseshoe orbit, but I'm sure that's not what you're talking about. Anything bigger than an asteroid we'd certainly know about it from centuries of observing the motions of the planets.

[Kryptid]

Kryptid, i propose it became thrown there by the migration of jupiter, formed in the gap between earth and jupiter, mars was one of its waywars satelites !

Jupiter's migration would have happened very early in the Solar System's development (billions of years ago). If counter-Earth was thrown into our orbit by that event, then it must have happened billions of years ago and thus must have remained in that orbit for billions of years in order to still be there in the present day. As others have stated before, it's extremely unlikely for such an orbit to be stable for that long.

[Petrochemicals (OP)]

Well why is the asteroid belt so stable, varying masses by more than we are on about here , equal orbits, little disturbance .

[Janus]

Well why is the asteroid belt so stable, varying masses by more than we are on about here , equal orbits, little disturbance .

Asteroids are always being subject to various tugs and pulls and variations of their orbits.  No individual asteroid maintains an unchanging orbit.   When disturbed they just take up a new position in the belt.  The fact that the asteroid belt remains, on average, the same is not the same as a single body maintaining a perfect position opposite of the Earth.  Even the asteroid belt has "No go" areas called Kirkwood gaps, which tend to be swept clean of asteroids due to various gravitational pulls on them. 

[Petrochemicals (OP)]

Well why is the asteroid belt so stable, varying masses by more than we are on about here , equal orbits, little disturbance .

The fact that the asteroid belt remains, on average, the same

I thought i said that

[chiralSPO]

Well why is the asteroid belt so stable, varying masses by more than we are on about here , equal orbits, little disturbance .

The fact that the asteroid belt remains, on average, the same

I thought i said that

Yes, you said that the asteroid belt stays roughly the same. Janus says that it's irrelevant...

The fact that the asteroid belt remains, on average, the same is not the same as a single body maintaining a perfect position opposite of the Earth.

[jeffreyH]

Johannes Kepler was working on the decades worth of observations of the orbit of Mars made by Tycho Brahe when he discovered the elliptical nature of planetary orbits. I think he may have noticed and mentioned an anomaly. Let the idea die. It is nonsense.

[Kryptid]

Well why is the asteroid belt so stable, varying masses by more than we are on about here , equal orbits, little disturbance .

Whoever said they are in equal orbits? The asteroid belt is over 200 million miles thick. That's much larger than the distance between the Earth and the Sun. It's not at all comparable to two planets being on opposite sides of the Sun with the exact same orbital distance.

[Bored chemist]

Which would be hidden by the sun

Saying this twice doesn't make it true (it does make you look a bit silly)

[Janus]

Well why is the asteroid belt so stable, varying masses by more than we are on about here , equal orbits, little disturbance .

Whoever said they are in equal orbits? The asteroid belt is over 200 million miles thick. That's much larger than the distance between the Earth and the Sun. It's not at all comparable to two planets being on opposite sides of the Sun with the exact same orbital distance.

Right they are spread out over a huge range of orbital distances, have different eccentricities and inclinations that vary as much as 30° from the ecliptic.   Trying to compare the asteroid belt to a body orbiting exactly opposite of the Sun is like saying that the a swarm of bees maintaining roughly the same shape overall is the same as two planes flying in perfect formation.

[Petrochemicals (OP)]

But asteroids in the asteroid belt is stable enough to orbit in a balanced constant mannor, so we agree then that all is left to do is to visually confirm the planet on the opposite side of the sun.

https://en.m.wikipedia.org/wiki/Ceres_(dwarf_planet)

2.767 au 1682 days orbit

https://en.m.wikipedia.org/wiki/2_Pallas

 2.771 1685 days orbit

Now does this seem a little bit more plausable

[Kryptid]

so we agree then that all is left to do is to visually confirm the planet on the opposite side of the sun.

It's almost as if you haven't read any of the replies in this thread...

https://en.m.wikipedia.org/wiki/Ceres_(dwarf_planet)

2.767 au 1682 days orbit

https://en.m.wikipedia.org/wiki/2_Pallas

 2.771 1685 days orbit

Now does this seem a little bit more plausable

Except Pallas and Ceres are not on opposite sides of the Sun from each other. The two approach each other every 4.6 years: http://saj.matf.bg.ac.rs/158/pdf/061-066.pdf

[Bored chemist]

But asteroids in the asteroid belt is stable enough to orbit in a balanced constant mannor

One of the  relatively few things we know about the asteroid belt is that the orbits are not stable.
From time to time they get kicked out and go on trips across the rest of the solar system.
Some of them hit  Earth.
https://en.wikipedia.org/wiki/Asteroid_belt#Meteorites

So, the thing most of us actually agree on is that you are wrong, for a number of reasons.

[Petrochemicals (OP)]

It's almost as if you haven't read any of the replies in this thread...

Except Pallas and Ceres are not on opposite sides of the Sun from each other. The two approach each other every 4.6 years: http://saj.matf.bg.ac.rs/158/pdf/061-066.pdf

And yet they continue on there orbits, without being attracted to the same position ? Approach after approach ?

[Bored chemist]

It's almost as if you haven't read any of the replies in this thread...

Except Pallas and Ceres are not on opposite sides of the Sun from each other. The two approach each other every 4.6 years: http://saj.matf.bg.ac.rs/158/pdf/061-066.pdf

And yet they continue on there orbits, without being attracted to the same position ? Approach after approach ?

What do you mean by that?
Are you expecting them to somehow synchronise or collide?
That's obviously impossible since they have to obey the laws of conservation of both momentum and energy.

[chiralSPO]

Petrochemicals,

This question appears to be solidly asked and answered. If you wish to continue defending you theory, then I suggest we continue in the "New Theories" sub-forum (you can start a new thread with a similar title, or I can split off part of this discussion and move it there.)

The "Physics, Astronomy & Cosmology" sub-forum is intended for discussions mostly within the framework of generally accepted science. Together, generally accepted theories of gravitation and orbital mechanics, as well as observations of our solar system from antiquity until now indicate with high certainty that there cannot be an Earth-sized planet on the other side of the sun.

[Petrochemicals (OP)]

Petrochemicals,

This question appears to be solidly asked and answered. If you wish to continue defending you theory, then I suggest we continue in the "New Theories" sub-forum (you can start a new thread with a similar title, or I can split off part of this discussion and move it there.)

The "Physics, Astronomy & Cosmology" sub-forum is intended for discussions mostly within the framework of generally accepted science. Together, generally accepted theories of gravitation and orbital mechanics, as well as observations of our solar system from antiquity until now indicate with high certainty that there cannot be an Earth-sized planet on the other side of the sun.

I will leave it at that as conjecture only and inconclusive. Thank you !

[Janus]

It's almost as if you haven't read any of the replies in this thread...

Except Pallas and Ceres are not on opposite sides of the Sun from each other. The two approach each other every 4.6 years: http://saj.matf.bg.ac.rs/158/pdf/061-066.pdf

And yet they continue on there orbits, without being attracted to the same position ? Approach after approach ?

Pallas and Ceres actually have quite different orbits despite the resonance of the periods. Pallas' orbit is more eccentric and is inclined by ~35 degrees to the ecliptic compared to Ceres at ~10.6,  The longitude of their ascending nodes are over 90 degrees apart.    Whether or not stable resonances can exist between orbiting bodies (they can) is not the issue. The issue is whether or not two bodies holding positions opposite the sun of each other is one of those stable resonances.    It is not.  Other patterns or arrangements can be stable, but this particular arrangement in not one of them.  This isn't opinion, but the result of the same orbital mechanics that says that the other resonances are possible.

[Colin2B]

Petrochemicals,

This question appears to be solidly asked and answered.

I will leave it at that as conjecture only and inconclusive. Thank you !

The answers given are not inconclusive.

[Bored chemist]

Petrochemicals,

This question appears to be solidly asked and answered. If you wish to continue defending you theory, then I suggest we continue in the "New Theories" sub-forum (you can start a new thread with a similar title, or I can split off part of this discussion and move it there.)

The "Physics, Astronomy & Cosmology" sub-forum is intended for discussions mostly within the framework of generally accepted science. Together, generally accepted theories of gravitation and orbital mechanics, as well as observations of our solar system from antiquity until now indicate with high certainty that there cannot be an Earth-sized planet on the other side of the sun.

I will leave it at that as conjecture only and inconclusive. Thank you !

Why would you do that?
It is perfectly clear that any "counter Earth" would have to be  tiny  in order not to be noticed.
Even then, it wouldn't be stable.