Core beliefs
The core beliefs of astrology were prevalent in parts of the ancient world and are epitomized in the Hermetic maxim, "as above, so below". Tycho Brahe used a similar phrase to summarize his studies in astrology: suspiciendo despicio, "by looking up I see downward".[14] Although the principle that events in the heavens are mirrored by those on Earth was once generally held in most traditions of astrology around the world, in the West there has historically been a debate among astrologers over the nature of the mechanism behind astrology. The debate also covers whether or not celestial bodies are only signs or portents of events, or if they are actual causes of events through some sort of force or mechanism.[citation needed]
Although the connection between celestial mechanics and terrestrial dynamics was explored first by Isaac Newton with his development of a universal theory of gravitation, claims that the gravitational effects of the celestial bodies are what accounts for astrological generalizations are not substantiated by scientific research, nor are they advocated by most astrologers.[citation needed]
Most astrological traditions are based on the relative positions and movements of various real or construed celestial bodies and on the construction of implied or calculated celestial patterns as seen at the time and place of the event being studied. These are chiefly the astrological planets, dwarf planets, the asteroids, the stars, the lunar nodes, Arabic parts and hypothetical planets. The frame of reference for such apparent positions is defined by the tropical or sidereal zodiac of twelve signs on one hand, and by the local horizon (ascendant-descendant axis) and midheaven-imum coeli axis on the other. This latter (local) frame is typically further divided into the twelve astrological houses. Furthermore, the astrological aspects are used to determine the geometric/angular relationship(s) between the various celestial bodies and angles in the horoscope.
Predictive astrology, in the Western tradition, employs two main methods: astrological transits and astrological progressions. In astrological transits the ongoing movements of the planets are interpreted for their significance as they transit through space and the horoscope. In astrological progressions the horoscope is progressed forward in time according to set methods. In Vedic astrology the focus is on planetary periods to infer the trend while transits are used to time significant events. Most Western astrologers no longer try to forecast actual events, but focus instead on general trends and developments. By comparison, Vedic astrologers predict both trends and events. Skeptics respond that this practice of western astrologers allows them to avoid making verifiable predictions, and gives them the ability to attach significance to arbitrary and unrelated events, in a way that suits their purpose.[15]
In the past, astrologers often relied on close observation of celestial objects and the charting of their movements. Modern astrologers use data provided by astronomers which are transformed to a set of astrological tables called ephemerides,[16] showing the changing zodiacal positions of the heavenly bodies through time.
TraditionsZodiac signs, 16th century European woodcut