ASTROLOGY

– throughout the Middle Ages, astrology and astronomy were closely linked in both the Western and the Arabic worlds.
Although astrology was used for prediction, pre-modern astrology required a substantial command of mathematics and an informed astronomical knowledge.

PTOLEMY – ‘ The Almagest ’ how the planets move; ‘ Tetrabiblos ’ what effect the qualities of the planets (Mars – hot & dry, Moon – cold & wet [affect on the tides]) and their relative positions will have.

Belief that the influence of the planets may have an effect on earthly health and other matters (disease and character traits).

Tables of positions of planets became developed from the Babylonian originals in the Islāmic world.

Alphonsine tables produced for King Alphonso X of Castile in 1275.

Prognostication repeatedly condemned by the Church as influence of the planets denies the concept of free will.

Refutation of astrology is difficult owing to its complexity.

NEXT buttonNEXT

Advertisements

CLAUDIUS PTOLEMY (c.90-168)

(NOT to be confused with the royal dynasty of the Ptolemys)

c.150 – Alexandria, Egypt

‘The Earth is at the centre of all the cosmos’

This erroneous belief dominated astronomy for 14 centuries.

‘The Earth does not rotate; it remains at the centre of things because this is its natural place – it has no tendency to go either one way or the other. Around it and in successively larger spheres revolve the Moon, Mercury, Venus, the Sun, Mars, Jupiter and Saturn, all of them deriving their motion from the immense and outermost spheres of fixed stars’. Ptolemy wrote in the thirteen-volume Almagest (Arabic for ‘The Greatest’), in which he synthesised the work of his predecessors. It provided a definitive compilation of all that was known and accepted in the field of astronomy up to that point.

Almagest’s eminence, importance and influence can only be compared with Euclid’s Elements. A major part of Almagest deals with the mathematics of planetary motion. Ptolemy explained the wandering of the planets by a complicated system of cycles and epicycles. Starting from the Aristotelian notion that the earth was at the centre of the universe, with the stars and the planets rotating in perfect circles around it, the Ptolemaic system argued for a system of ‘deferents’, or large circles, rotating around the earth, and eighty epicycles, or small circles, which circulated within the deferents. He also examined theories of ‘movable eccentrics’. These proposed just one circle of rotation, with its centre slightly offset from the earth, as well as ‘equants’ – imaginary points in space that helped define the focal point of the rotation of the celestial bodies. Ptolemy’s texts were written with such authority that later generations struggled for a thousand years to convincingly challenge his theories and they remained the cornerstone of Western and Arab astronomy until the sixteenth century.

Ptolemy’s theory was challenged by COPERNICUS and demolished by KEPLER. Ptolemy supported Eratosthenes’ view that the Earth is spherical.

Ptolemy’s other major text is his Tetrabiblos, a founding work on the then science of astrology.

Despite that Ptolemy’s ideas of a geocentric universe have been shown to be erroneous by modern researchers it must be remembered that at the time the observable phenomena would support this view of the cosmos. Without a more informed understanding of the mechanisms involved it can appear that heavenly bodies do in fact move according to the Ptolemaeic model and mathematical evidence was available to provide verification and vindication.

 Medieval Astronomy from Melk Abbey Credit: Paul Beck (Univ. Vienna), Georg Zotti (Vienna Inst. Arch. Science) Copyright: Library of Melk Abbey, Frag. 229  Explanation: Discovered by accident, this manuscript page provides graphical insight to astronomy in medieval times, before the Renaissance and the influence of Nicolaus Copernicus, Tycho de Brahe, Johannes Kepler, and Galileo. The intriguing page is from lecture notes on astronomy compiled by the monk Magister Wolfgang de Styria before the year 1490 at Melk Abbey in Austria. The top panels clearly illustrate the necessary geometry for a lunar (left) and solar eclipse in the Earth-centered Ptolemaic system. At lower left is a diagram of the Ptolemaic view of the solar system and at the lower right is a chart to calculate the date of Easter Sunday in the Julian calendar. Text at the upper right explains the movement of the planets according to the Ptolemaic system. The actual manuscript page is on view at historic Melk Abbey as part of a special exhibition during the International Year of Astronomy.

Library of Melk Abbey, Frag. 229

Wikipedia-logo © (link to wikipedia)

NEXT buttonNEXT

NEXT buttonTHE STARS

Related sites
  • The Almagest (thesevenworlds.wordpress.com)

THE MEDIEVAL ARAB SCIENTISTS

A great deal of what we know about the ancient world and its scientific ideas has come to us from documents which were translated from ancient Greek or other ancient languages into Arabic, and later from Arabic into European languages. The material reached the Arab world in many cases through the Roman empire in the East, Byzantium, which survived until 1453, almost a thousand years after the fall of Rome, during the period known in Europe as the Dark Ages.
During this time the consolidating influence of Islāmic religion saw Arab Muslims begin to build an empire that was to stretch across the Middle East and across North Africa into Spain. At the heart of the Islāmic world the caliphs ruled in Baghdad. Arab scientists sowed the seeds that would later be reaped in the scientific revolution of the seventeenth century, especially under the Abbasid dynasty during the caliphate of Harun al-Rashid and his son al-Mamun, and the Middle East became the intellectual hub of the World.

depiction of early islamic scholars at work at various scientific investigations

In the ninth century, at the House of Wisdom – a mixture of library, research institute and university – scholars worked to translate the great works of the GREEK thinkers. Muslim scholars of this golden age made important and original contributions to mathematics and astronomy, medicine and chemistry. They developed the ASTROLABE, which enabled astronomers to measure the position of the stars with unparalleled accuracy.Astrology & Astronomy in Iran and Ancient Mesopotamia: Astrolabe: An ancient astronomical instrument
In medicine they made the first serious studies of drugs and advanced surgery. A number of mathematicians, including Habash al-Hasib (‘he who calculates’), Abul’l-Wafa al-Buzjani, Abu Nasr al-Iraq and Ibn Yunus formulated trigonometry (including all six trig functions [ sin, cosec, cos, sec, tan, and cot ]) at a level far above that introduced by the Greek astronomer-mathematician HIPPARCHUS in the second century BCE.
It is largely through such efforts that Greek ideas were preserved through the DARK AGES.

more

Eight hundred years before COPERNICUS, a model of the solar system was advanced with the Earth as a planet orbiting the Sun along with other planets.

A few centuries later this idea fell into disfavour with the early Christian Church, which placed mankind at the centre of the universe in a geo-centric model. The alternative teaching would be deemed heresy punishable by death and it would not be until the seventeenth century that the work of GALILEO, KEPLER and NEWTON gave credence to the ideas revitalized by Copernicus in 1543.

It is worth noting that even to-day at least half the named stars in the sky bear Arabic names (Aldebaran and Algol amongst others) and many terms used in astronomy, such as Nadir and Azimuth, are originally Arabic words.

 The Ulugh Beg Observatory in Samarkand, Uzbekistan

The elaborate observatory established by the Ulugh Begg in Samarkand in the fifteenth century appeared to function with a dictum meant to challenge PTOLEMY’s geocentric picture of the universe sanctioned by the Church in Europe. Arabic scholars had access to the early teachings of ARISTARCHUS, the astronomer from Samos of the third century BCE. (referred to by Copernicus in the forward of an early draft of De Revolutionibus, although omitted from the final copy)

NEXT buttonNEXT

JOHN DEE (1527-1608)

1590 – London, England

portrait of john dee

JOHN DEE

‘Mathematician, cartographer & astronomer. Prolific author, natural magician, alchemist.’

‘Alternative knowledge and methods of learning. ‘Conversations with Angels’. Human power over the world (neo-Platonism).’

Dee was a Hermetic philosopher, a major influence on the ROSICRUCIANS, possibly a spy – astrologer and adviser to Queen Elizabeth I ; he chose the day of her coronation.

One of the greatest scholars of his day. His library in his home in Mortlake, London, contained more than 3,000 books.

Greatly influenced by Edward Kelley (1555- 97), whom he met in 1582; from 1583-1589 Dee and Kelley sought the patronage of assorted mid-European noblemen and kings, eventually finding it from the Bohemian Count Vilem Rosenberg.

In 1589, Dee left Kelley to his alchemical research and returned to England where Queen Elizabeth I granted him a position as a college warden, but he had lost respect owing to his occult reputation. Dee returned to Mortlake in 1605 in poor health and increasing poverty and ended his days as a common fortune-teller.

Wikipedia-logo © (link to wikipedia)

NEXT buttonTIMELINE

FRED HOYLE (1915-2001)

1957 – UK

‘stellar nucleosynthesis’

Photograph of FRED HOYLE ©

FRED HOYLE

‘Most of the elements heavier than hydrogen in the universe are created, or synthesised in stars when lighter nuclei fuse to make heavier nuclei’

The Sun burns, or fuses, hydrogen to helium. This process occurs during most of every star’s lifetime. After a star exhausts its supply of hydrogen, the star burns helium to form beryllium, carbon and oxygen. When the star exhausts its supply of helium it shrinks and its temperature rises to 1000million degrees. The rising temperature triggers a new series of reactions in which carbon, oxygen and other elements combine to form iron and nickel. When the star has burned everything into iron and nickel, it explodes as a supernova. The elements heavier than nickel are formed during supernova explosions.

Hoyle proposed this theory in 1957. Hoyle, along with Thomas Gold and Herman Bondi, had also proposed the steady state theory of the origin of the universe in 1948.

Link to WIKIPEDIA

NEXT buttonTIMELINE

NEXT buttonTHE STARS

English: The oldest star of our Galaxy: HE 152...

The oldest star of our Galaxy: HE 1523-0901 (Photo credit: Wikipedia)