The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south

celestial latitude In astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e.g. ...

of the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

– the apparent path of 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 ...

across the

celestial sphere In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, ...

over the course of the year. Within this zodiac belt appear 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 ...

and the brightest

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

s, along their orbital planes. The zodiac is divided along the ecliptic into 12 equal parts, called " signs", each occupying 30° of

celestial longitude In astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e.g. ...

. These signs roughly correspond to the

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

s with the following modern names:

Aries Aries may refer to: *Aries (astrology), an astrological sign *Aries (constellation), a constellation in the zodiac Arts, entertainment and media * ''Aries'' (album), by Luis Miguel, 1993 * ''Aries'' (EP), by Alice Chater, 2020 * "Aries" (song), ...

Taurus Taurus is Latin for 'bull' and may refer to: * Taurus (astrology), the astrological sign ** Vṛṣabha, in vedic astrology * Taurus (constellation), one of the constellations of the zodiac * Taurus (mythology), one of two Greek mythological ch ...

Gemini Gemini most often refers to: * Gemini (constellation), one of the constellations of the zodiac * Gemini (astrology), an astrological sign Gemini may also refer to: Science and technology Space * Gemini in Chinese astronomy, the Gemini constellat ...

Cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

Leo Leo is the Latin word for lion. It most often refers to: * Leo (constellation), a constellation of stars in the night sky * Leo (astrology), an astrological sign of the zodiac * Leo (given name), a given name in several languages, usually mas ...

Virgo Virgo may refer to: Arts and entertainment * Virgo (film), a 1970 Egyptian film * Virgo (character), several Marvel Comics characters * Virgo Asmita, a character in the manga ''Saint Seiya: The Lost Canvas'' * ''Virgo'' (album), by Virgo Four, ...

Libra Libra generally refers to: * Libra (constellation), a constellation * Libra (astrology), an astrological sign based on the star constellation Libra may also refer to: Arts and entertainment * ''Libra'' (novel), a 1988 novel by Don DeLillo Musi ...

, Scorpio,

Sagittarius Sagittarius ( ) may refer to: *Sagittarius (constellation) *Sagittarius (astrology), a sign of the Zodiac * Sagittarius of Gap, a 6th century bishop *Sagittarius A*, the supermassive black hole at the center of the Milky Way galaxy Ships *'' S ...

, Capricorn, Aquarius, and

Pisces Pisces may refer to: *Pisces (astrology), an astrological sign Astronomy *Pisces (constellation), a constellation ** Pisces Overdensity, an overdensity of stars in the Milky Way's halo that is situated in the Pisces constellation ** Pisces II, a ...

. The signs have been used to determine the time of the year by identifying each sign with the days of the year the Sun is in the respective sign. In

Western astrology Western astrology is the system of astrology most popular in Western countries. It is historically based on Ptolemy's '' Tetrabiblos'' (2nd century CE), which in turn was a continuation of Hellenistic and ultimately Babylonian traditions. West ...

, and formerly

astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

, the time of each sign is associated with different attributes. The zodiacal system and its angular measurement in 360

sexagesimal Sexagesimal, also known as base 60, is a numeral system with 60 (number), sixty as its radix, base. It originated with the ancient Sumerians in the 3rd millennium BC, was passed down to the ancient Babylonians, and is still used—in a modified fo ...

degree (°) originated with

Babylonian astronomy Babylonian astronomy was the study or recording of celestial objects during the early history of Mesopotamia. The numeral system used, sexagesimal, was based on 60, as opposed to ten in the modern decimal system. This system simplified the ca ...

during the

1st millennium BC File:1st millennium BC.jpg, 400x400px, From top left clockwise: The Parthenon, a former temple in Athens, Greece; Aristotle, Greek philosopher; Gautama Buddha, a spiritual teacher and the founder of Buddhism; Wars of Alexander the Great last from ...

. It was communicated into

Greek astronomy Ancient Greek astronomy is the astronomy written in the Greek language during classical antiquity. Greek astronomy is understood to include the Ancient Greece, Ancient Greek, Hellenistic period, Hellenistic, Roman Empire, Greco-Roman, and Late an ...

by the 2nd century BC, as well as into developing the Hindu zodiac. Due to the

precession of the equinoxes In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's Rotation around a fixed axis, rotational axis. In the absence of precession, the astronomical body's orbit would show ...

, the time of year that the Sun is in a given constellation has changed since Babylonian times, and the point of

March equinox The March equinox or northward equinox is the equinox on the Earth when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the ver ...

has moved from

into

. The zodiac forms a

celestial coordinate system In astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e. ...

, or more specifically an

ecliptic coordinate system In astronomy, the ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small So ...

, which takes the ecliptic as the origin of latitude and the Sun's position at

vernal equinox Spring equinox or vernal equinox or variations may refer to: * March equinox, the spring equinox in the Northern Hemisphere * September equinox, the spring equinox in the Southern Hemisphere Other uses * Nowruz, Persian/Iranian new year which be ...

as the origin of longitude. In modern astronomy, the ecliptic coordinate system is still used for tracking Solar System objects.

Name

The English word ' derives from , the Latinized form of the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

( ), meaning "cycle or circle of little animals". () is the diminutive of (, "animal"). The name reflects the prominence of animals (and

mythological hybrid Hybrid beasts are creatures composed of parts from different animals, including humans, appearing in the folklore of a variety of cultures as legendary creatures. In burial sites Remains similar to those of mythological hybrids have been found ...

s) among the twelve signs. In English, the term "zodiac" may also be used in reference to or translation for the similar twelve year cycle (also sometimes applied to other time units than years) of the East Asian-derived systems referred to as the

Chinese zodiac The Chinese zodiac is a traditional classification scheme based on the Chinese calendar that assigns an animal and its reputed attributes to each year in a repeating twelve-year (or duodenary) cycle. The zodiac is very important in traditional ...

(see also,

Earthly Branches The Earthly Branches (also called the Terrestrial Branches or the 12-cycle) are a system of twelve ordered symbols used throughout East Asia. They are indigenous to China, and are themselves Chinese characters, corresponding to words with no co ...

): similarities include the use of animal or theriomorphic figures associated with a twelve year cycle used culturally to allege or describe personality traits, life events, and their interrelationships—thus this use in translation.

Usage

The zodiac was in use by the

Roman era In modern historiography, ancient Rome is the Roman people, Roman civilisation from the founding of Rome, founding of the Italian city of Rome in the 8th century BC to the Fall of the Western Roman Empire, collapse of the Western Roman Em ...

, based on concepts inherited by

Hellenistic astronomy Ancient Greek astronomy is the astronomy written in the Greek language during classical antiquity. Greek astronomy is understood to include the Ancient Greek, Hellenistic, Greco-Roman, and late antique eras. Ancient Greek astronomy can be divided ...

from

of the Chaldean period (mid-1st millennium BC), which, in turn, derived from an earlier system of lists of stars along the ecliptic. The construction of the zodiac is described in

Ptolemy Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...

's comprehensive 2nd century AD work, the ''

Almagest The ''Almagest'' ( ) is a 2nd-century Greek mathematics, mathematical and Greek astronomy, astronomical treatise on the apparent motions of the stars and planetary paths, written by Ptolemy, Claudius Ptolemy ( ) in Koine Greek. One of the most i ...

''. Although the zodiac remains the basis of the

in use in

besides the equatorial one, the term and the names of the twelve signs are today mostly associated with

horoscopic astrology Horoscopic astrology is a form of astrology that uses a horoscope, a visual representation of the heavens, for a specific moment in time to interpret the purported meaning behind the alignment of the planets at that moment. The idea is that the pl ...

. The term "zodiac" may also refer to the region of the

encompassing the paths of the planets corresponding to the band of about 8 arc degrees above and below the ecliptic. The zodiac of a given planet is the band that contains the path of that particular body; e.g., the "zodiac of the Moon" is the band of 5° above and below the ecliptic. By extension, the "zodiac of the comets" may refer to the band encompassing most

short-period comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or coma surrounding the nucleus, and ...

History

Early history

As early as the 14th century BC a complete list of the 36 Egyptian

decan The decans (; Egyptian ''bꜣktw'' or ''baktiu'', "

hose A hose is a flexible hollow tube or pipe designed to carry fluids from one location to another, often from a faucet or hydrant. Early hoses were made of leather, although modern hoses are typically made of rubber, canvas, and helically wound w ...

connected with work") are 36 groups of stars (small constellations) used in the Egyptian astronomy, ancient Egyptian astronomy to conveniently divide the 360 degree ecliptic into 36 parts ...

s was placed among the hieroglyphs adorning the tomb of

Seti I Menmaatre Seti I (or Sethos I in Greek language, Greek) was the second pharaoh of the Nineteenth Dynasty of Egypt during the New Kingdom of Egypt, New Kingdom period, ruling or 1290 BC to 1279 BC. He was the son of Ramesses I and Sitre, and th ...

; they figured again in the temple of

Ramesses II Ramesses II (sometimes written Ramses or Rameses) (; , , ; ), commonly known as Ramesses the Great, was an Pharaoh, Egyptian pharaoh. He was the third ruler of the Nineteenth Dynasty of Egypt, Nineteenth Dynasty. Along with Thutmose III of th ...

, and characterize every Egyptian astrological monument. Both the famous zodiacs of

Dendera Dendera ( ''Dandarah''; ; Bohairic ; Sahidic ), also spelled ''Denderah'', ancient Iunet 𓉺𓈖𓏏𓊖 “jwn.t”, Tentyris,(Arabic: Ewan-t إيوان-ة ), or Tentyra is a small town and former bishopric in Egypt situated on the west bank of ...

display their symbols, identified by

Karl Richard Lepsius Karl Richard Lepsius (; 23 December 181010 July 1884) was a German people, Prussian Egyptology, Egyptologist, Linguistics, linguist and modern archaeology, modern archaeologist. He is widely known for his opus magnum ''Denkmäler aus Ägypten ...

Antoninus Pius Drachm showing a Zodiac wheel

The division of the ecliptic into the zodiacal signs originates in

during the first half of the

. The zodiac draws on stars in earlier

Babylonian star catalogues Babylonian astronomy collated earlier observations and divinations into sets of Babylonian star catalogues, during and after the Kassite rule over Babylonia. These star catalogues, written in cuneiform script, contained lists of constellations, ...

, such as the MUL.APIN catalogue, which was compiled around 1000 BC. Some constellations can be traced even further back, to Bronze Age (

Old Babylonian Empire The Old Babylonian Empire, or First Babylonian Empire, is dated to , and comes after the end of Sumerian power with the destruction of the Third Dynasty of Ur, and the subsequent Isin-Larsa period. The chronology of the first dynasty of Babylon ...

) sources, including

"The Twins", from "The Great Twins";

"The Crab", from "The Crayfish", among others. Around the end of the fifth century BC,

Babylonia Babylonia (; , ) was an Ancient history, ancient Akkadian language, Akkadian-speaking state and cultural area based in the city of Babylon in central-southern Mesopotamia (present-day Iraq and parts of Kuwait, Syria and Iran). It emerged as a ...

n astronomers divided the ecliptic into 12 equal "signs", by analogy to 12 schematic months of 30 days each. Each sign contained 30° of

, thus creating the first known celestial coordinate system. According to calculations by modern astrophysics, the zodiac was introduced between 409 and 398 BC, during Persian rule, and probably within a very few years of 401 BC. Unlike modern astrologers, who place the beginning of the sign of

at the position of the Sun at the

in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

(

), Babylonian astronomers fixed the zodiac in relation to stars, placing the beginning of

at the "Rear Twin Star" ( β Geminorum) and the beginning of Aquarius at the "Rear Star of the Goat-Fish" ( δ Capricorni). Due to the

, the time of year the Sun is in a given constellation has changed since Babylonian times, as the point of March equinox has moved from

into

. Because the divisions were made into equal arcs of 30° each, they constituted an ideal system of reference for making predictions about a planet's longitude. However, Babylonian techniques of observational measurements were in a rudimentary stage of evolution. They measured the position of a planet in reference to a set of "normal stars" close to the ecliptic (±9° of latitude). The normal stars were used as observational reference points to help position a planet within this ecliptic coordinate system. In

Babylonian astronomical diaries The Babylonian astronomical diaries are a collection of Babylonian cuneiform texts written in Akkadian language that contain systematic records of astronomical observations and political events, predictions based on astronomical observations, weat ...

, a planet position was generally given with respect to a zodiacal sign alone, though less often in specific degrees within a sign. When the degrees of longitude were given, they were expressed with reference to the 30° of the zodiacal sign, i.e., not with a reference to the continuous 360° ecliptic. In astronomical

ephemerides In astronomy and celestial navigation, an ephemeris (; ; , ) is a book with tables that gives the trajectory of naturally occurring astronomical objects and artificial satellites in the sky, i.e., the position (and possibly velocity) over time. ...

, the positions of significant astronomical phenomena were computed in

fractions of a degree (equivalent to

minutes and seconds of arc A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

). For daily ephemerides, the daily positions of a planet were not as important as the astrologically significant dates when the planet crossed from one zodiacal sign to the next.

Hebrew astronomy and astrology

Knowledge of the Babylonian zodiac is said to be reflected in the

Hebrew Bible The Hebrew Bible or Tanakh (;"Tanach"
. '' E. W. Bullinger interpreted the creatures that appear in the

book of Ezekiel The Book of Ezekiel is the third of the Nevi'im#Latter Prophets, Latter Prophets in the Hebrew Bible, Tanakh (Hebrew Bible) and one of the Major Prophets, major prophetic books in the Christian Bible, where it follows Book of Isaiah, Isaiah and ...

( 1:10) as the middle signs of the four quarters of the zodiac, with the Lion as

, the Bull as

, the Man as Aquarius and the Eagle as a higher aspect of Scorpio. Some authors have linked the signs of the zodiac with the

twelve tribes of Israel The Twelve Tribes of Israel ( , ) are described in the Hebrew Bible as being the descendants of Jacob, a Patriarchs (Bible), Hebrew patriarch who was a son of Isaac and thereby a grandson of Abraham. Jacob, later known as Israel (name), Israel, ...

, and with the lunar

Hebrew calendar The Hebrew calendar (), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance and as an official calendar of Israel. It determines the dates of Jewish holidays and other rituals, such as '' yahrze ...

, which has twelve

lunar months In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona, Middle Eastern, and Euro ...

in a

lunar year A lunar calendar is a calendar based on the monthly cycles of the Moon's phases (synodic months, lunations), in contrast to solar calendars, whose annual cycles are based on the solar year, and lunisolar calendars, whose lunar months are brought ...

Martin Martin may refer to: Places Antarctica * Martin Peninsula, Marie Byrd Land * Port Martin, Adelie Land * Point Martin, South Orkney Islands Europe * Martin, Croatia, a village * Martin, Slovakia, a city * Martín del Río, Aragón, Spain * M ...

and others have argued that the arrangement of the tribes around the

Tabernacle According to the Hebrew Bible, the tabernacle (), also known as the Tent of the Congregation (, also Tent of Meeting), was the portable earthly dwelling of God used by the Israelites from the Exodus until the conquest of Canaan. Moses was instru ...

(reported in the

Book of Numbers The Book of Numbers (from Biblical Greek, Greek Ἀριθμοί, ''Arithmoi'', , ''Bəmīḏbar'', ; ) is the fourth book of the Hebrew Bible and the fourth of five books of the Jewish Torah. The book has a long and complex history; its final f ...

) corresponded to the order of the zodiac, with Judah,

Reuben Reuben or Reuven is a Biblical male first name from Hebrew רְאוּבֵן (Re'uven), meaning "behold, a son". In the Bible, Reuben was the firstborn son of Jacob. Variants include Reuvein in Yiddish or as an English variant spelling on th ...

Ephraim Ephraim (; , in pausa: ''ʾEp̄rāyīm'') was, according to the Book of Genesis, the second son of Joseph ben Jacob and Asenath, as well as the adopted son of his biological grandfather Jacob, making him the progenitor of the Tribe of Ephrai ...

, and

Dan Dan or DAN may refer to: People * Dan (name), including a list of people with the name ** Dan (king), several kings of Denmark * Dan people, an ethnic group located in West Africa ** Dan language, a Mande language spoken primarily in Côte d'Ivo ...

representing the middle signs of Leo, Aquarius, Taurus, and Scorpio, respectively. Such connections were taken up by

Thomas Mann Paul Thomas Mann ( , ; ; 6 June 1875 – 12 August 1955) was a German novelist, short story writer, social critic, philanthropist, essayist, and the 1929 Nobel Prize in Literature laureate. His highly symbolic and ironic epic novels and novell ...

, who in his novel ''

Joseph and His Brothers ''Joseph and His Brothers'' (, ) is a four-part novel by Thomas Mann, written over the course of 16 years. Mann retells the familiar stories of Genesis, from Jacob to Joseph (chapters 27–50), setting it in the historical context of the ...

'', attributes characteristics of a sign of the zodiac to each tribe, in his rendition of the

Blessing of Jacob The Blessing of Jacob is a prophetic poem that appears written in Genesis at and mentions each of Jacob's twelve sons. Genesis presents the poem to be the words of Jacob himself to his sons when he is about to die. Linguistically, it's dated t ...

Hellenistic and Roman era

The Babylonian star catalogs entered

in the 4th century BC, via

Eudoxus of Cnidus Eudoxus of Cnidus (; , ''Eúdoxos ho Knídios''; ) was an Ancient Greece, ancient Greek Ancient Greek astronomy, astronomer, Greek mathematics, mathematician, doctor, and lawmaker. He was a student of Archytas and Plato. All of his original work ...

. Babylonia or

Chaldea Chaldea () refers to a region probably located in the marshy land of southern Mesopotamia. It is mentioned, with varying meaning, in Neo-Assyrian cuneiform, the Hebrew Bible, and in classical Greek texts. The Hebrew Bible uses the term (''Ka� ...

in the Hellenistic world came to be so identified with astrology that "Chaldean wisdom" became among

Greeks Greeks or Hellenes (; , ) are an ethnic group and nation native to Greece, Greek Cypriots, Cyprus, Greeks in Albania, southern Albania, Greeks in Turkey#History, Anatolia, parts of Greeks in Italy, Italy and Egyptian Greeks, Egypt, and to a l ...

and

Romans Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of Roman civilization *Epistle to the Romans, shortened to Romans, a letter w ...

the synonym of

divination Divination () is the attempt to gain insight into a question or situation by way of an occultic ritual or practice. Using various methods throughout history, diviners ascertain their interpretations of how a should proceed by reading signs, ...

through the

planets A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets by the most restrictive definition of the te ...

and

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

s. Hellenistic astrology derived in part from Babylonian and Ancient Egyptian astronomy, Egyptian astrology. Horoscopic astrology first appeared in Ptolemaic Kingdom, Ptolemaic Egypt (305 BC–30 BC). The Dendera zodiac, a relief dating to , is the first known depiction of the classical zodiac of twelve signs. The earliest extant Greek text using the Babylonian division of the zodiac into 12 signs of 30 equal degrees each is the ''Anaphoricus'' of Hypsicles of Alexandria (fl.190BC). Particularly important in the development of Western horoscopic astrology was the astrologer and astronomer Tetrabiblos, Ptolemy, whose work ''Tetrabiblos'' laid the basis of the Western astrological tradition. Under the Greeks, and Ptolemy in particular, the planets, Houses, and signs of the zodiac were rationalized and their function set down in a way that has changed little to the present day. Ptolemy lived in the 2nd century AD, three centuries after the discovery of the precession of the equinoxes by Hipparchus around 130 BC. Hipparchus' lost work on precession never circulated very widely until it was brought to prominence by Ptolemy, and there are few explanations of precession outside the work of Ptolemy until late Antiquity, by which time Ptolemy's influence was widely established. Ptolemy clearly explained the theoretical basis of the western zodiac as being a tropical astrology, tropical coordinate system, by which the zodiac is aligned to the equinoxes and solstices, rather than the visible constellations that bear the same names as the zodiac signs.

Hindu zodiac

According to mathematician-historian Jean-Étienne Montucla, Montucla, the Hindu zodiac was adopted from the Ancient Greek astronomy, Greek zodiac through communications between ancient India and the Greek empire of Bactria. The Hindu zodiac uses the Sidereal astrology, sidereal coordinate system, which makes reference to the fixed stars. The tropical zodiac (of Mesopotamian origin) is divided by the intersections of the

and equator, which shifts in relation to the backdrop of fixed stars at a rate of 1° every 72 years, creating the phenomenon known as precession of the equinoxes. The Hindu zodiac, being sidereal, does not maintain this seasonal alignment, but there are still similarities between the two systems. The Hindu zodiac signs and corresponding Greek signs sound very different, being in Sanskrit and Greek respectively, but their symbols are nearly identical. For example, ''dhanu'' means "bow" and corresponds to Sagittarius, the "archer", and ''kumbha'' means "water-pitcher" and corresponds to Aquarius, the "water-carrier".

Middle Ages

Angers Cathedral South Rose Window of Christ with Zodiac

During the Abbasid Caliphate, Abbasid era, Greek reference books were translated into Arabic, and Astronomy in the medieval Islamic world, Islamic astronomers then did their own observations, correcting Ptolemy's Almagest. One such book was Abd al-Rahman al-Sufi, Al-Sufi's ''Book of Fixed Stars'', which has pictorial depictions of 48 constellations. The book was divided into three sections: constellations of the zodiac, constellations north of the zodiac, and southern constellations. When Al-Sufi's book, and other works, were translated in the 11th century, there were mistakes made in the translations. As a result, some stars ended up with the names of the constellation they belong to (e.g. Hamal in Aries). The High Middle Ages saw a revival of interest in Greco-Roman magic, first in Kabbalism and later continued in Renaissance magic. This included magical uses of the zodiac, as found, e.g., in the Sefer Raziel HaMalakh. The zodiac is found in medieval stained glass as at Angers Cathedral, where the master glass maker, André Robin, made the ornate rosette window, rosettes for the North and South transepts after the fire there in 1451.

Medieval Islamic era

Ottoman Sundial at the Debbane Palace museum

Astrology emerged in the 8th century AD as a distinct discipline in Islam, with a mix of Indian, Hellenistic Iranian and other traditions blended with Greek and Islamic astronomical knowledge, for example Ptolemy's work and Al-Sufi's Book of Fixed Stars. A knowledge of the influence that the stars have on events on the earth was important in Islamic civilization. As a rule, it was believed that the signs of the zodiac and the planets control the destiny not only of people but also of nations, and that the zodiac has the ability to determine a person's physical characteristics as well as intelligence and personal traits. The practice of astrology at this time could be divided into four broader categories: Natal astrology, Genethlialogy, Catarchic Astrology, Interrogational Astrology and General Astrology. However the most common type of astrology was Genethlialogy, which examined all aspects of a person's life in relation to the planetary positions at their birth; more commonly known as our horoscope. Astrology services were offered widely across the empire, mainly in bazaars, where people could pay for a reading. Astrology was valued in the royal courts, for example, the Abbasid Caliph Al-Mansur used astrology to determine the best date for founding the new capital of Baghdad. While horoscopes were generally widely accepted by society, many scholars condemned the use of astrology and divination, linking it to occult influences. Many theologians and scholars thought that it went against the tenets of Islam; as only God should be able to determine events rather than astrologers looking at the positions of the planets. In order to calculate someone's horoscope, an astrologer would use three tools: an astrolabe, ephemeris and a takht. First, the astrologer would use an astrolabe to find the position of the sun, align the rule with the persons time of birth and then align the rete to establish the altitude of the sun on that date. Next, the astrologer would use an ephemeris, a table denoting the mean position of the planets and stars within the sky at any given time. Finally, the astrologer would add the altitude of the sun taken from the astrolabe, with the mean position of the planets on the person's birthday, and add them together on the takht (also known as the dustboard). The dust board was merely a tablet covered in sand; on which the calculations could be made and erased easily. Once this had been calculated, the astrologer was then able to interpret the horoscope. Most of these interpretations were based on the zodiac in literature. For example, there were several manuals on how to interpret each zodiac sign, the treatise relating to each individual sign and what the characteristics of these zodiacs were.

Early modern

An example of the use of signs as astronomical coordinates may be found in the ''Nautical Almanac and Astronomical Ephemeris for the year 1767''. The "Longitude of the Sun" columns show the sign (represented as a digit from 0 to and including 11), degrees from 0 to 29, minutes, and seconds. Mughal Empire, Mughal king Jahangir issued an attractive series of coins in gold and silver depicting the twelve signs of the zodiac. File:P.9 a volvella of the moon. A volvella is a moveable device for working out the position of the sun and moon in the zodiac.jpg, A volvella of the moon. A volvella is a moveable device for working out the position of the Sun and Moon in the zodiac, 15th century File:Monasterio de Svetitskhoveli, Miskheta, Georgia, 2016-09-29, DD 41.jpg, 17th-century fresco of Christ in the zodiac circle, Svetitskhoveli, Cathedral of Living Pillar, Georgia (country), Georgia

Twelve signs

What follows is a list of the signs of the modern zodiac (with the ecliptic longitudes of their first points), where 0° Aries is understood as the vernal equinox, with their Latin, Greek, Sanskrit, and Babylonian names. But the Sanskrit and the name equivalents (after c.500 BC) denote the constellations only, not the tropical zodiac signs. The "English translation" is not usually used by English speakers. The Latin names are standard English usage (except that "Capricorn" is used rather than "Capricornus"). These twelve signs have been arranged into a nursery rhyme as a mnemonic device: Another mnemonic is ''A Tense Gray Cat Lay Very Low, Sneaking Slowly, Contemplating A Pounce''. The following table compares the Gregorian calendar, Gregorian dates on which the Sun enters a sign in the Ptolemaic tropical astrology, tropical zodiac, and a sign in two sidereal astrology, sidereal systems: one proposed by Cyril Fagan, and a fourteen-sign system proposed by Steven Schmidt which adds Ophiuchus (see below) and Cetus (the International Astronomical Union, IAU boundaries of which just graze by the ecliptic): Zodiac German Woodcut

The beginning of Aries is defined as the moment of March equinox, vernal equinox, and all other dates shift accordingly. The precise Gregorian times and dates vary slightly from year to year as the Gregorian calendar shifts relative to the tropical year. These variations remain within less than two days' difference in the recent past and the near-future, vernal equinox in Universal Time, UT always falling either on 20 or 21 March in the period of 1797 to 2043, falling on 19 March in 1796 the last time and in 2044 the next. The vernal equinox has fallen on 20 March UT since 2008, and will continue to do so until 2043.

As each sign takes up exactly 30 degrees of the zodiac, the average duration of the solar stay in each sign is one twelfth of a sidereal year, or 30.43 standard days. Due to Earth's slight orbital eccentricity, the duration of each sign varies appreciably, between about 29.4 days for Capricorn and about 31.4 days for Cancer (see Equation of time). In addition, because the Earth's axis is at an angle, some signs take longer to rise than others, and the farther away from the equator the observer is situated, the greater the difference. Thus, signs are spoken of as Ascendant, "long" or "short" ascension.

Constellations

In Sidereal and tropical astrology, tropical astrology, the astrological sign, zodiacal signs are distinct from the

s associated with them, not only because of their drifting apart due to the precession of equinoxes but because the physical constellations take up varying widths of the ecliptic, so the Sun is not in each constellation for the same amount of time. Thus, Virgo (constellation), Virgo takes up 5 times as much ecliptic longitude as Scorpius (constellation), Scorpius. The zodiacal signs are an abstraction from the physical constellations, and each represent exactly th of the full circle, but the time spent by the Sun in each sign varies slightly due to the eccentricity of the Earth's orbit. Sidereal and tropical astrology, Sidereal astrology assigns the zodiac sign approximately to the corresponding constellation. This alignment needs recalibrating every so often to keep the alignment in place. The ecliptic intersects with 13 constellations of

's ''

'', as well as of the more precisely delineated IAU designated constellations. In addition to the twelve constellations after which the twelve zodiac signs are named, the ecliptic intersects Ophiuchus, the bottom part of which interjects between Scorpius and Sagittarius. Occasionally this difference between the astronomical constellations and the astrological signs is mistakenly reported in the popular press as a "change" to the list of traditional signs by some astronomical body like the IAU, NASA, or the Royal Astronomical Society. This happened in a 1995 report of the ''BBC Nine O'Clock News'' and various reports in 2011 and 2016. Some "parazodiacal" constellations are touched by the paths of the planets, leading to counts of up to 25 "constellations of the zodiac". The ancient Babylonian MUL.APIN catalog lists Orion (constellation), Orion, Perseus (constellation), Perseus, Auriga (constellation), Auriga, and Andromeda (constellation), Andromeda. Modern astronomers have noted that planets pass through Crater (constellation), Crater, Sextans, Cetus, Pegasus (constellation), Pegasus, Corvus (constellation), Corvus, Hydra (constellation), Hydra, Orion (constellation), Orion, and Scutum (constellation), Scutum, with Venus very rarely passing through Aquila (constellation), Aquila, Canis Minor, Auriga (constellation), Auriga, and Serpens. Some other constellations are mythologically associated with the zodiacal ones: Piscis Austrinus, The Southern Fish, is attached to Aquarius. In classical maps, it swallows the stream poured out of Aquarius' pitcher, but perhaps it formerly just swam in it. Aquila (constellation), Aquila, The Eagle, was possibly associated with the zodiac by virtue of its main star, Altair. Hydra (constellation), Hydra in the Early Bronze Age marked the celestial equator and was associated with Leo, which is shown standing on the serpent on the Dendera zodiac.

Precession of the equinoxes

The zodiac system was developed in Neo-Babylonian, Babylonia, some 2,500 years ago, during the "Age of Aries". At the time, it is assumed, the precession of the equinoxes was unknown. Contemporary use of the coordinate system is presented with the choice of interpreting the system either as sidereal astrology, sidereal, with the signs fixed to the Fixed stars, stellar background, or as tropical astrology, tropical, with the signs fixed to the point (Euclidean vector, vector of the Sun) at the

takes the tropical approach, whereas Hindu astrology takes the sidereal one. This results in the originally unified zodiacal coordinate system drifting apart gradually, with a clockwise (westward) precession of 1.4 degrees per century. For the tropical zodiac used in Western astronomy and astrology, this means that the tropical ''sign'' of Aries currently lies somewhere within the ''constellation'' Pisces ("Age of Pisces"). The sidereal coordinate system takes into account the ayanamsa, ''ayan'' meaning "transit" or "movement", and ''amsa'' meaning 'small part', i.e. movement of equinoxes in small parts. It is unclear when Indians became aware of the precession of the equinoxes, but Bhāskara II's 12th-century treatise ''Siddhanta Shiromani'' gives equations for measurement of precession of equinoxes, and says his equations are based on some lost equations of ''Suryasiddhanta'' plus the equation of Munjaala. The discovery of precession is attributed to Hipparchus around 130 BC. Ptolemy quotes from Hipparchus' now-lost work entitled "On the Displacement of the Solstitial and Equinoctial Points" in the seventh book of his 2nd century astronomical text, ''Almagest'', where he describes the phenomenon of precession and estimates its value. Ptolemy clarified that the convention of Greek mathematical astronomy was to commence the zodiac from the point of the vernal equinox and to always refer to this point as "the first degree" of Aries. This is known as the "tropical zodiac" (from the Greek word trópos, turn) because its starting point revolves through the circle of background constellations over time. The principle of the vernal point acting as the first degree of the zodiac for Greek astronomers is described in the 1st century BC astronomical text of Geminus of Rhodes. Geminus explains that Greek astronomers of his era associate the first degrees of the zodiac signs with the two solstices and the two equinoxes, in contrast to the older Chaldean (Babylonian) system, which placed these points within the zodiac signs. This illustrates that Ptolemy merely clarified the convention of Greek astronomers and did not originate the principle of the tropical zodiac, as is sometimes assumed. Ptolemy demonstrates that the principle of the tropical zodiac was well known to his predecessors within his astrological text, the ''Tetrabiblos'', where he explains why it would be an error to associate the regularly spaced signs of the seasonally aligned zodiac with the irregular boundaries of the visible constellations:

In modern astronomy

Astronomically, the zodiac defines a belt of space extending 8° or 9° in celestial latitude to the north and south of the

, within which the orbits of the Moon and the principal planets remain. It is a feature of the ecliptic coordinate system – a

centered upon the ecliptic (the plane of the Earth's orbit and the Sun's apparent path), by which

is measured in degrees east of the vernal equinox (the ascending intersection of the ecliptic and equator). The zodiac is narrow in angular terms because most of the Sun's planets have orbits that have only a slight Orbital inclination, inclination to the Orbital plane (astronomy), orbital plane of the Earth. Stars within the zodiac are subject to occultations by the Moon and other solar system bodies. These events can be useful, for example, to estimate the cross-sectional dimensions of a minor planet, or check a star for a close companion. Zodiacal Light Seen from Paranal

The Sun's placement upon the vernal equinox, which occurs annually around 21 March, defines the starting point for measurement, the first degree of which is historically known as the "First Point of Aries, first point of Aries". The first 30° along the ecliptic is nominally designated as the zodiac sign Aries, which no longer falls within the proximity of the constellation Aries since the effect of precession is to move the vernal point through the backdrop of visible constellations. It is currently located near the end of the constellation Pisces, having been within that constellation since the 2nd century AD. The subsequent 30° of the ecliptic is nominally designated the zodiac sign Taurus, and so on through the twelve signs of the zodiac so that each occupies th (30°) of the zodiac's great circle. Zodiac signs have never been used to determine the boundaries of astronomical constellations that lie in the vicinity of the zodiac, which are, and always have been, irregular in their size and shape. The convention of measuring celestial longitude within individual signs was still being used in the mid-19th century, but modern astronomy now numbers degrees of celestial longitude continuously from 0° to 360°, rather than 0° to 30° within each sign. This coordinate system is primary used by astronomers for observations of solar system objects. The use of the zodiac as a means to determine astronomical measurement remained the main method for defining celestial positions by Western astronomers until the Renaissance, at which time preference moved to the equatorial coordinate system, which measures astronomical positions by right ascension and declination rather than the ecliptic-based definitions of celestial longitude and

. The orientation of equatorial coordinates are aligned with the Earth's axis of rotation, rather than the plane of the planet's orbit around the Sun. The word "zodiac" is used in reference to the zodiacal cloud of dust grains that move among the planets, and the zodiacal light that originates from their scattering of sunlight. While its name is derived from the zodiac, the zodiacal light covers the entire night sky, with enhancements in certain directions.

Unicode characters

In Unicode, the symbols of zodiac signs are encoded in block "Miscellaneous Symbols". They can be forced to look like text by appending U+FE0E, or like emojis by appending U+FE0F:

References

External links

"A Treatise on Zodiacal Signs and Constellations: Unique Jewels on the Benefits of Keeping Time"
– a manuscript that dates back to 1831 with a focus on Arabic, Coptic and Syriac calendars. {{DEFAULTSORT:Zodiac, The Astrological signs, Z Constellations, + Ancient astronomy Astrology Astronomical coordinate systems Birthdays Early scientific cosmologies Western astrology