Noun
counter-earth (plural not attested)
A hypothetical planet sharing an orbit with the earth, but on the opposite side of the sun.
counter-Earth
Alternative form of counter-earth
Counter-Earth Along with the Central Fire, the "mysterious" Counter-Earth (Antichthon) was the other heavenly body not visible from Earth. Source: Internet
Greek Pythagorean universe further Philolaus believed there was a "Counter-Earth" (Antichthon) orbiting the "Central Fire" (not labeled) that was not visible from Earth. Source: Internet
Since "counter" means "opposite", and opposite could only be in respect to the Central Fire, it follows that the Counter-Earth must be orbiting 180 degrees from Earth. Source: Internet
The Counter-Earth is L3.) The arrows indicate the gradients of the potential around the five Lagrange points—downhill toward them ( red ) or away from them ( blue ). Source: Internet
The idea of a Counter-Earth waned after the heliocentric model of the solar system became widely accepted from the 16th century. Source: Internet