thumb|250px|right|Philolaus believed there was a "Counter-Earth" (Antichthon) orbiting the "Central Fire" (not labeled) that was not visible from Earth. The upper illustration depicts Earth at night while the lower one depicts Earth in the day. The Counter-Earth is a hypothetical body of the Solar System that orbits on the other side of the Solar System from Earth, e.g. at the L3 Lagrange point of the Sun–Earth system. A Counter-Earth, or Antichthon (), was hypothesized by the pre-Socratic Greek philosopher Philolaus () to support his non-geocentric cosmology, in which all objects in the unive
thumb|250px|right|Philolaus believed there was a "Counter-Earth" (Antichthon) orbiting the "Central Fire" (not labeled) that was not visible from Earth. The upper illustration depicts Earth at night while the lower one depicts Earth in the day. The Counter-Earth is a hypothetical body of the Solar System that orbits on the other side of the Solar System from Earth, e.g. at the L3 Lagrange point of the Sun–Earth system. A Counter-Earth, or Antichthon (), was hypothesized by the pre-Socratic Greek philosopher Philolaus () to support his non-geocentric cosmology, in which all objects in the universe revolve around a "Central Fire" (unseen from Earth and distinct from the Sun which also revolves around it).
In modern times, a hypothetical planet always on the other side of the Sun from Earth has been called a "Counter-Earth", and has been a recurring theme in UFO claims, as well as in fiction (particularly science fiction).
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).