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.
Western astrology is largely horoscopic, that is, it is a form of divination based on the construction of a horoscope for an exact moment, such as a person's birth as well as the location (since time zones may or may not affect a person's birth chart), in which various cosmic bodies are said to have an influence. Astrology in western popular culture is often reduced to sun sign astrology, which considers only the individual's date of birth (i.e. the "position of the Sun" at that date).
Astrology is a pseudoscience and has consistently failed experimental and theoretical verification.
Astrology was widely considered a respectable academic and scientific field before the Enlightenment, but modern research has found no consistent empirical basis to it.
Core principles
A central principle of astrology is integration within the cosmos. The individual, Earth, and its environment are viewed as a single organism, all parts of which are correlated with each other. Cycles of change that are observed in the heavens are therefore reflective (not causative) of similar cycles of change observed on earth and within the individual. This relationship is expressed in the Hermetic maxim "as above, so below; as below, so above", which postulates symmetry between the individual as a microcosm and the celestial environment as a macrocosm.
As opposed to Sidereal astrology, Western astrology evaluates a person's birth based on the alignments of the stars and planets from the perspective on earth instead of in space.
At the heart of astrology is the metaphysical principle that mathematical relationships express qualities or 'tones' of energy which manifest in numbers, visual angles, shapes and sounds – all connected within a pattern of proportion. An early example is Ptolemy, who wrote influential texts on all these topics. Al-Kindi, in the 9th century, developed Ptolemy's ideas in De Aspectibus which explores many points of relevance to astrology and the use of planetary aspects.
The zodiac
The zodiac is the belt or band of constellations through which the Sun, Moon, and planets move on their journey across the sky. Astrologers noted these constellations and so attached a particular significance to them. Over time they developed the system of twelve signs of the zodiac, based on twelve of the constellations through which the sun passes throughout the year, those constellations that are "Enlightened by the mind". Most western astrologers use the tropical zodiac beginning with the sign of Aries at the Northern Hemisphere vernal equinox always on or around March 21 of each year. The Western Zodiac is drawn based on the Earth's relationship to fixed, designated positions in the sky, and the Earth's seasons. The Sidereal Zodiac is drawn based on the Earth's position in relation to the constellations, and follows their movements in the sky.
Due to a phenomenon called precession of the equinoxes (where the Earth's axis slowly rotates like a spinning top in a 25,700-year cycle), there is a slow shift in the correspondence between Earth's seasons (and calendar) and the constellations of the zodiac. Thus, the tropical zodiac corresponds with the position of the earth in relation to fixed positions in the sky (Western Astrology), while the sidereal zodiac is drawn based on the position in relation to the constellations (sidereal zodiac).
The twelve signs
In modern Western astrology the signs of the zodiac are believed to represent twelve basic personality types or characteristic modes of expression. The twelve signs are divided into four elements fire, earth, air and water. Fire and air signs are considered masculine, while water and earth signs are considered feminine. The twelve signs are also divided into three qualities, also called modalities, Cardinal, fixed and mutable.
+Western Astrology TableLatin NameGlossSymbolUnicode CharacterApproximate Sun Sign DatesEcliptic Longitude(a ≤ < b)HousePolarityTriplicityModalityModern RulerClassic RulerGreek nameSanskrit nameSumero-Babylonian nameMUL.APIN; Peter Whitfield, History of Astrology (2001); W. Muss-Arnolt, The Names of the Assyro-Babylonian Months and Their Regents, Journal of Biblical Literature (1892). AriesThe Ram♈︎March 21 – April 190° to 30°1PositiveFireCardinalMars (Krios) () "Agrarian Worker", Dumuzi TaurusThe Bull♉︎April 20 – May 2030° to 60°2NegativeEarthFixedVenus (Tauros) () "Divine Bull of Heaven" GeminiThe Twins♊︎May 21 – June 2060° to 90°3PositiveAirMutableMercury (Didymoi) () "Great Twins" (Castor & Pollux) CancerThe Crab ()♋︎June 21 – July 2290° to 120°4NegativeWaterCardinalMoon (Karkinos) () "Crayfish" LeoThe Lion♌︎July 23 – August 22120° to 150°5PositiveFireFixedSun (Leōn) () "Lion" VirgoThe Maiden♍︎August 23 – September 22150° to 180°6NegativeEarthMutableMercury (Parthenos) () "The Furrow"* *"The goddess Shala's ear of grain" LibraThe Scales♎︎September 23 – October 22180° to 210°7PositiveAirCardinalVenus (Zygos) (तुला) "Scales" ScorpioThe Scorpion♏︎October 23 – November 21210° to 240°8NegativeWaterFixedPlutoMars (Skorpios)Alternative form: Skorpiōn. Later form (with synizesis): . () "Scorpion" SagittariusThe Archer (Centaur)♐︎November 22 – December 21240° to 270°9PositiveFireMutableJupiter (Toxotēs) (ष), Nedu "soldier" CapricornThe Goat ()♑︎December 22 – January 19270° to 300°10NegativeEarthCardinalSaturn (Aigokerōs) () "Goat-Fish" of Enki AquariusThe Water-bearer♒︎January 20 – February 18300° to 330°11PositiveAirFixedUranusSaturn (Hydrokhoos) () "Great One", later "pitcher" PiscesThe Fish♓︎February 19 – March 20330° to 360°12NegativeWaterMutableNeptuneJupiter (Ikhthyes) () "Tail of the Swallow"; DU.NU.NU "fish-cord"
Note: these are only approximations and the exact date on which the sign of the sun changes varies from year to year.
Sun-sign astrology
Newspapers often print astrology columns which purport to provide guidance on what might occur in a day in relation to the sign of the zodiac that included the sun when the person was born. Astrologers refer to this as the "sun sign", but it is often commonly called the "star sign". These predictions are vague or general; so much so that even practicing astrologers consider them of little to no value on their own. Experiments have shown that when people are shown a newspaper horoscope for their own sign along with a newspaper horoscope for a different sign, they judge them to be equally accurate on average.The Forer Effect Other tests have been performed on complete, personalized horoscopes cast by professional astrologers, and have shown no correlation between the horoscope results and the person it was cast for.The AstroTest , An account of a test of the predictive power of astrology, with references to other experiments.
The planets
In modern Western astrology the planets represent basic drives or impulses in the human psyche. These planets differ from the definition of a planet in astronomy in that the Sun, Moon, and recently, Pluto are all considered to be planets for the purposes of astrology. Each planet is also said to be the ruler of one or two zodiac signs. The three outer planets (Uranus, Neptune, Pluto) have each been assigned rulership of a zodiac sign by astrologers. Traditionally rulership of the signs was, according to Ptolemy, based on seasonal derivations and astronomical measurement, whereby the luminaries being the brightest planets were given rulership of the brightest months of the year and Saturn the coldest furthest classical planet was given to the coldest months of the year, with the other planets ruling the remaining signs as per astronomical measurement. It is noteworthy that the modern rulerships do not follow the same logic.
Classical planets
The astrological 'planets' are the seven heavenly bodies known to the ancients. The Sun and Moon, also known as 'the lights', are included as they were thought to act like the astronomical planets. Astrologers call inner planets Mercury, Venus and Mars, the 'personal planets', as they represent the most immediate drives. The 'lights' symbolise respectively the existential and sensitive fundamentals of the individuality.
The following table summarizes the rulership by the seven classically known planetsPlanet description of each of the twelve astrological signs, together with their effects on world events, people and the earth itself as understood in the Middle Ages.
+ Traditional planets with their rulership of signs and effects on people and the world Symbol Planet Rules the sign Effect on world events Person's nature Effect in life Effect in earth Sun Leo
Wisdom, generosity, 'sunny' disposition Good fortune Gold Moon Cancer
Wandering Travel, lunacy Silver Mercury Gemini and Virgo Action Changeability, eagerness, quickness, 'mercurial' temperament Rapid change Mercury (quicksilver) Venus Libra and Taurus Fortunate events Beauty, amorousness Good luck Copper Mars Aries, classically also Scorpio War Strength, endurance, 'martial' temperament Conflicts, misfortune Iron Jupiter Sagittarius, classically also Pisces Good times, prosperity Cheerful, magnanimous, 'jovial' temperament Good fortune Tin Saturn Capricorn, classically also Aquarius Disastrous events Wisdom, stability, persistence, 'saturnine' temperament Accidents, disease, treachery, bad luck Lead
Modern modifications to the Ptolemaic system
Additional planets These are the planets discovered in modern times, which have since been assigned meanings by Western astrologers.
+ Planets discovered in modern times, with signs and effects Symbol Planet Representing Rules the sign Claimed effects on world events Claimed effects on people Uranus (a) Platinum as a planetary metal; (b) monogram 'H' for planet's discoverer, William Herschel Aquarius Innovation, technology Sudden or disruptive change Neptune Trident, weapon of sea-god Neptune Pisces Change of contemporary musical taste Confusion, sensitivity Pluto (a) Pluto's bident; (b) PL monogram for astronomer Percival Lowell who predicted a planet beyond Neptune Scorpio Demolition of old, bad political systems Transformation, fate, death
Sidereal and tropical astrology
There are two camps of thought among western astrologers about the "starting point", 0 degrees Aries, in the zodiac. Sidereal astrology uses a fixed starting point in the background of stars, while tropical astrology, used by the majority of Western astrologers, chooses as a starting point the position of the Sun against the background of stars at the Northern hemisphere vernal equinox (i.e. when the Sun position against the heavens crosses over from the southern hemisphere to the northern hemisphere) each year. The consequence of the Tropical approach is that when we say the Sun or a planet is in a certain zodiac sign, observation of it in the sky will show that it does not lie within that constellation at all.The Primer of Sidereal Astrology," Cyril Fagin and Brigadier R. C. Firebrace, American Federation of Astrologers, Inc., (1971)
As the Earth spins on its axis, it "wobbles" like a top, causing the vernal equinox to move gradually backwards against the star background, (a phenomenon known as the Precession of the equinoxes) at a rate of about 30 degrees (one Zodiacal sign length) every 2,160 years. Thus the two zodiacs would be aligned only once every 26,000 years. They were aligned about 2,000 years ago when the zodiac was originally established.
This phenomenon gives us the conceptual basis for the Age of Aquarius, whose "dawning" coincides with the movement of the vernal equinox across the cusp from Pisces to Aquarius in the star background.
The moon's nodes