The Counter-Earth is a hypothetical body of the Solar System that orbits on the other side of the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

. A Counter-Earth or ''Antichthon'' () was hypothesized by the

pre-Socratic Pre-Socratic philosophy, also known as early Greek philosophy, is ancient Greek philosophy before Socrates. Pre-Socratic philosophers were mostly interested in cosmology, the beginning and the substance of the universe, but the inquiries of the ...

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

philosopher Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...

Philolaus Philolaus (; , ''Philólaos''; ) was a Greek Pythagorean and pre-Socratic philosopher. He was born in a Greek colony in Italy and migrated to Greece. Philolaus has been called one of three most prominent figures in the Pythagorean tradition and ...

() to support his non- geocentric

cosmology Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe, the cosmos. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', with the meaning of "a speaking of the wo ...

, in which all objects in the universe revolve around a "Central Fire" (unseen from Earth and distinct from the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

which also revolves around it). In modern times a hypothetical planet always on the other side of the Sun from

has been called a "Counter-Earth", and has been a recurring theme in UFO claims, as well as in fiction (particularly

science fiction Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, space ...

Greek Pythagorean universe

An astronomical system positing that the Earth, Moon, Sun, planets and unseen "counter-earth" revolve around an unseen "Central Fire" was developed in the 5th century BC and attributed to the Pythagorean

. Philolaus' universe moved "the earth from the center of the cosmos,"Philolaus
Stanford Encyclopedia of Philosophy, Carl Huffman. and provided the insight that "the apparent motion of the heavenly bodies" was (in large part) due to "the real motion of the observer"—i.e. Earth. In Philolaus' system, the Earth and Counter-Earth revolved around the unseen Central Fire every 24 hours, while the Moon's revolution was monthly, and the Sun's yearly. It was the Earth's speedy travel past the slower moving Sun that resulted in the appearance on Earth of the Sun rising and setting. Further from the Central Fire, the Planets' movement was slower still, and the outermost "sky" (i.e. stars) probably fixed.

Counter-Earth

Along with the Central Fire, the "mysterious" Counter-Earth (''Antichthon'') was the other heavenly body not visible from Earth.

Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...

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 (such as astronomer John Louis Emil Dreyer) have thought that Philolaus had it following an orbit such that it was always located between Earth and the Central Fire. However, Burch argues that Philolaus must have thought that 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. According to Aristotle—a critic of the Pythagoreans—the function of the Counter-Earth was to explain "eclipses of the moon and their frequency", which could not be explained by Earth alone blocking the light of the Sun if Earth did not revolve around the Sun. Aristotle suggested that it was also introduced "to raise the number of heavenly bodies around the central fire from nine to ten, which the Pythagoreans regarded as the perfect number".Burch, George Bosworth. The Counter-Earth
''Osirus'', vol. 11. Saint Catherines Press, 1954. p. 267-294 However, Burch believes Aristotle was having a joke "at the expense of Pythagorean number theory," and that the true purpose of the Counter-Earth was to "balance" Philolaus' cosmos—balance being needed because without a counter there would be only one dense, massive object in the system—Earth. Although his system had both the Earth and the Planets orbiting a single point, the

ancient Greeks Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically re ...

did not consider Earth a "planet." In the time before

Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

could observe from his telescope that planets were spheres like Earth, they were thought to be different from stars only in brightness and in their motion, and like stars composed of a fiery or ethereal matter having little or no density. However, the Earth was obviously made of the dense elements of earth and water. According to Burch,

If there was a single Earth revolving at some distance from the center of space, then the universe's center of gravity, located in the Earth as its only dense body, would not coincide with its spatial center ... The universe, consequently, would be off center, so to speak—lopsided and asymmetric—a notion repugnant to any Greek, and doubly so to a Pythagorean.

This could be corrected by another body with the same mass as Earth, orbiting the same central point but 180 degrees from Earth—the Counter-Earth.

Later

In the 1st century AD, after the idea of a spherical Earth had gained more general acceptance,

Pomponius Mela Pomponius Mela, who wrote around AD 43, was the earliest known Roman geographer. He was born at the end of the 1st century BC in Tingentera (now Algeciras) and died AD 45. His short work (''De situ orbis libri III.'') remained in use nea ...

, a Latin cosmographer, developed an updated version of the idea, wherein a

spherical Earth Spherical Earth or Earth's curvature refers to the approximation of the figure of the Earth as a sphere. The earliest documented mention of the concept dates from around the 5th century BC, when it appears in the writings of Ancient Greek philos ...

must have a more or less balanced distribution of land and water, even though all known continents were in the northern hemisphere. Mela drew a map which postulated a continental landmass in the unknown, southern half of Earth—the antipodes—below the equator and the tropics,

clime The climes (singular ''clime''; also ''clima'', plural ''climata'', from Greek κλίμα ''klima'', plural κλίματα ''klimata'', meaning "inclination" or "slope") in classical Greco-Roman geography and astronomy were the divisions of ...

s which he believed uninhabitable and impassably hot. Mela ascribed the name " Antichthones" to the inhabitants of this continent.Pomponius Mela. ''de Chorographia''.

Modern era

Philolaus's ideas were all eventually superseded by the modern realization that a spherical Earth rotating on its own axis was one of several spherical planets following the laws of gravity and revolving around a much larger Sun. The idea of a Counter-Earth waned after the heliocentric model of the solar system became widely accepted from the 16th century. In the contemporary world, "Counter-Earth" usually refers to a hypothetical planet with an orbit as Burch described, on the other side of the "Central Fire"—i.e. the Sun. It cannot be seen from Earth, not because Earth faces away from the center, but because the Sun's great size blocks its view. It has been a recurring motif in fiction—often serving as an

allegory As a List of narrative techniques, literary device or artistic form, an allegory is a wikt:narrative, narrative or visual representation in which a character, place, or event can be interpreted to represent a meaning with moral or political signi ...

for the real Earth—and UFO claims.The Ufo Book of Lists
By STEPHEN J SPIGNESI, Stephen J. Spignesi, The 1968 '' Scientific Study of Unidentified Flying Objects'' headed by Edward Condon at the

University of Colorado The University of Colorado (CU) is a system of public universities in Colorado. It consists of four institutions: the University of Colorado Boulder, the University of Colorado Colorado Springs, the University of Colorado Denver, and the U ...

even included a "Numerical Experiment on the Possible Existence of an 'Anti-Earth as an appendix.

Detectability

A Counter-Earth could still be detected from the Earth for a number of reasons. Even if the Sun blocked its view from Earth, a Counter-Earth would have gravitational influence ( perturbation) upon the other planets, comets and man-made probes of the

. Researchers have detected no such influence, and indeed space probes sent to

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

and other places could not have successfully flown by or landed on their targets if a Counter-Earth existed, as the navigational calculations for their journeys did not take any putative Counter-Earth into account. Roughly speaking, anything larger than in diameter should have been detected.Could There Be a Planet Hidden on the Opposite Side of our Sun? PopSci asks the scientist who has peered around it
By Danny Freedman, PopSci , 20 April 2009 Any planetary-sized body 180 degrees from Earth should also have been visible to some space probes, such as NASA's

STEREO Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...

coronagraph probes (two spacecraft launched into orbits around the Sun in 2006, one farther ahead of and one behind the Earth's orbit) which would have seen the Counter-Earth 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. A Counter-Earth would also eventually be visible from Earth because the gravitational forces of the other planets on it would make its own orbit unstable.

has 82% of the mass of Earth and would come within 0.3 AU of the location of a Counter-Earth every 20 months, providing considerable gravitational pull that over the years would move its orbit into sight of observers on Earth.

In fiction

Counter-Earth has made appearances in fiction since the late 1800s. It is variously depicted as very similar to Earth or very different, and often employed as a vehicle for

satire Satire is a genre of the visual, literary, and performing arts, usually in the form of fiction and less frequently non-fiction, in which vices, follies, abuses, and shortcomings are held up to ridicule, often with the intent of exposin ...

. Counter-Earth being inhabited by counterparts of the people of Earth is a recurring theme. Variations on the concept also occasionally appear, including extrasolar equivalents, the

equivalent "Counter-Mars", and a planet hidden on the other side of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

rather than

Notes

M.Admin. (2014, March 26). The Bizarre Greek Theory About The Solar System. KnowledgeNuts. https://knowledgenuts.com/2014/03/26/the-bizarre-greek-theory-about-the-solar-system/

References

External links

* {{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Ancient Greek astronomy Early scientific cosmologies Pseudoastronomy Hypothetical bodies of the Solar System Hypothetical astronomical objects