The Knowledge Library

A permanent, connected reference for the living sky — the history, the instruments, the ideas of astrology and the people who shaped them. Not dated writing like the Almanac, but a growing web of entries built to be read, followed link to link, and cited.

The reading rooms

  • History — The long human story of reading the sky — the calendars, discoveries and machines that taught us to measure the heavens.
  • Instruments — How the sky was measured and modelled — from the astrolabe to the armillary sphere, the instruments that turned looking up into knowing.
  • Astrology — The concepts at the heart of the practice — the cycles, aspects and moving points that give the sky its meaning.
  • Astrologers — The astronomers, writers and observers behind the tradition — the lives and works the ideas were carried in.

Entries

  • The Antikythera Mechanism — An ancient Greek geared device, recovered in 1901 from a shipwreck off the island of Antikythera, that mechanically modelled the movements of the Sun and Moon and predicted eclipses. It is the oldest known analogue astronomical computer.
  • The Metonic Cycle — A period of about nineteen years after which the phases of the Moon fall on very nearly the same days of the solar year. 235 lunar months are almost exactly nineteen solar years — a near-perfect reconciliation of the Moon’s months with the Sun’s year.
  • The Astrolabe — An ancient instrument for measuring the altitude of stars and planets and for solving problems of time and position in the sky. Often called the first analogue computer, it let a single hand-held disc tell the time, find a body’s place and model the turning heavens.
  • The Armillary Sphere — A model of the heavens built from a nest of rings, each standing for an important circle of the sky — the celestial equator, the ecliptic, the tropics and the horizon. It shows, in three dimensions, how the sky is organised around a central Earth or Sun.
  • The Synodic Month — The average time from one New Moon to the next — about 29.53 days. It is the cycle of the Moon’s phases as seen from Earth, and the ‘month’ at the root of lunar and lunisolar calendars.
  • The Lunar Nodes — The two points where the Moon’s orbit crosses the ecliptic — the Sun’s apparent path. The ascending (North) node and descending (South) node drift slowly backward through the zodiac, and eclipses can happen only when a New or Full Moon falls near one of them.
  • The Void of Course Moon — The stretch of time when the Moon, having made its last major aspect in a sign, will make no more before it moves into the next. It is traditionally read as a pause — a time to rest and reflect rather than to begin something new.
  • Claudius Ptolemy — A Greco-Roman mathematician, astronomer and astrologer of the second century, working in Alexandria. His Almagest set out the geometry of the heavens that Europe and the Islamic world used for over a thousand years, and his Tetrabiblos became a foundational text of Western astrology.
  • William Lilly — A seventeenth-century English astrologer, the most famous of his age. His Christian Astrology (1647) was the first major textbook of astrology written in English rather than Latin, and his name is bound up with horary astrology — answering a question from the chart of the moment it is asked.