Along with the Central Fire, the "mysterious" Counter-Earth ("Antichthon") was the other heavenly body not visible from Earth. Aristotle described it as "another Earth", from which Greek scholar George Burch infers that it must be similar in size, shape and constitution to Earth. Some (astronomer John Louis Emil Dreyer) think Philolaus had it following an orbit so that it was always located between Earth and the Central Fire. This tenth planet is always invisible to observers on Earth, because it is between Earth and the central fire and always keeps pace with the Earth. A tale of Greek mythology may have placed it in that location to stop man from looking at the throne of Zeus directly. However, Burch argues Philolaus must have thought it orbited on the other side of the Fire from Earth. 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.