"Professor" Haesemeyer has shed some light on the alleged dark twin of Earth. This is a response he made on the India During Poleshift blog @ https://earthchanges.ning.com/profiles/blogs/india-during-poleshift:
Something that occurred to me was that ZT has this Dark Twin Theory. I did some research and apparently has only started up in conversation from ZT in 2004, and prior to that it was referred to as the Dead Twin in ZT which was actually PX.
From what I gather is that it was that the Sun had a Dead Twin (PX) and ever since 2003-2004 (when Earth halted in it's orbit according to ZT) it seemed to morph into a description of an Earth size Dark Twin in the same orbit as Earth, 180 degrees opposite the Sun.
Prior to ZT, I faintly recall a theory to this nature, but could find no reference. I would be aghast that ZT originated something original.
After further examination, I found a Marvel Comics published the same theory in in one of their comics in 1972. The Greeks had some mythology behind it also.
http://en.wikipedia.org/wiki/Counter-Earth_%28comics%29
There was a Counter Earth theory with scientific analysis.
If such a planet actually existed, according to present scientific cosmology, it would be permanently hidden behind the sun but nevertheless detectable from Earth, because of its gravitational influence upon the other planets of the Solar System. No such influence has been detected, and indeed space probes sent to Venus, Mars and other places could not have successfully flown by or landed on their targets if a Counter-Earth existed, as it was not accounted for in navigational calculation.
It must also be noted that the Earth orbit is not a circle but an ellipse, and in respect of Kepler's second law, a planet revolves faster when it is close to the star. So if the Counter-Earth followed the Earth on the same orbit with half a year of delay, it would sometimes be visible from Earth. Rather, to be hidden from Earth, the Counter-Earth would have an orbit symmetrical to Earth's one, not sharing the second focus.
The Sun-Jupiter Trojan asteroid system is an example of a stable Lagrange orbit. Equation 10 in section 14 of Lectures on Celestial Mechanics by Siegel and Moser shows the relation between the masses of the bodies and the distances between them in the case of a collinear orbit. However, these linear orbits are not as stable as, for example, the equilateral Lagrange orbits L4 and L5. Hilda asteroids do not visit L3 of Jupiter-Sun system, though they do come close to it in their curious orbits.
Any planetary sized body at Earth's L3 point should have been visible by the NASA STEREO coronagraphs during the first half of 2007. The separation of the STEREO spacecraft from Earth would give them a view of the L3 point during the early phase of the mission. Later, as the spacecraft continued to separate, the L3 point drifted out of the field of view. Given the sensitivity of STEREO's COR2 coronagraph, anything larger than 100 kilometres (62 mi) in diameter should have been detected.
http://en.wikipedia.org/wiki/Counter-Earth#References_in_culture
There have been a few films with the same theme,
Doppelgänger or outside Europe known as Journey to the Far Side of the Sun, 1969
Another Earth 2011
Melancholia, 2011
