Astrology to Astronomy - The Study of the Night Sky from Ptolemy to Copernicus - With Biographies and Illustrations

By Vintage Astronomy Classics

For countless millennia humans have read the future in the night sky and seen the effects of celestial movement here on Earth, this was astrology, the very first attempt to understand the stars and planets. In a very short amount of time mankind has come from the practice of astrology through the work of countless great men and women to the fully fledged scientific study of astronomy and cosmology. This book follows the train of thought and discovery taken by a few people. Including biographies of Ptolemy and Copernicus.

• Language: English
• Publisher: Vintage Astronomy Classics
• Release date: Aug 6, 2020
• ISBN: 9781528765879

Book preview

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ASTROLOGY

TO ASTRONOMY

THE STUDY OF THE NIGHT SKY

FROM PTOLEMY TO COPERNICUS

WITH BIOGRAPHIES

AND ILLUSTRATIONS

By

VARIOUS

Copyright © 2022 Vintage Astronomy Classics

This edition is published by Vintage Astronomy Classics,

an imprint of Read & Co.

This book is copyright and may not be reproduced or copied in any

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Contents

A BRIEF HISTORY OF ASTRONOMY

THE GEOMETRICAL PERIOD

A Chapter by George Forbes

I. PRIMITIVE ASTRONOMY AND ASTROLOGY

II. ANCIENT ASTRONOMY—THE CHINESE AND CHALDÆANS

III. ANCIENT GREEK ASTRONOMY

IV. THE REIGN OF EPICYCLES—FROM PTOLEMY TO COPERNICUS

PTOLEMY AND COPERNICUS

Chapters by Sir Robert S. Ball

PTOLEMY

COPERNICUS

A BRIEF

HISTORY OF ASTRONOMY

Astronomy is the oldest of the natural sciences, dating back to antiquity, with its origins in the religious, mythological and astrological practices of pre-history. Early cultures identified celestial objects with gods and spirits – and related these objects (and their movements) to worldly phenomena. Rains, droughts, seasons and tides were all explained via the heavenly realm. It is generally believed that the first ‘professional’ astronomers were priests and that their understanding of the skies was seen as ‘divine’, hence astronomy’s ancient connection to what is now called ‘astrology’. This area of knowledge, a complex mix of belief and science, has been developed all over the world – from cultures and countries as diverse as China, India, the ancient Egyptians, Mesopotamia, Mesoamerica, the medieval Islamic and the western world. It is, of course, still evolving today.

In the last couple of decades, our understanding of prehistoric European astronomy in particular has radically changed. This occurred with the discoveries of ancient astronomical artefacts such as the world’s oldest observatory, the ‘Goseck circle.’ Located in Germany, the site proves that Bronze Age Central Europeans had a much more sophisticated grasp of mathematics and astronomy than was previously assumed. According to Berlin archaeologist Klaus Goldmann, ‘European civilization goes further back than most of us ever believed.’ The enclosure is one of hundreds of similar wooden circular Henges built throughout Austria, Germany, and the Czech Republic during a 200-year period around 4,900 BC. While the sites vary in size (the one at Goseck is around 220 feet in diameter) they all have the same features: A narrow ditch surrounding a circular wooden wall, with a few large gates equally spaced around the outer edge. These gaps were used to observe the sun in the course of the calendar year and at the winter solstice, observers at the centre would have seen the sun rise and set through the south east and southwest gates.

The Ancient Greeks further developed astronomy, which they treated as a branch of mathematics, to a highly sophisticated level. The first geometrical, three-dimensional models to explain the apparent motion of the planets were developed in the fourth century BC by Eudoxus of Cnidus and Callippus of Cyzicus. Their models were based on nested homocentric spheres centred upon the Earth. A different approach to celestial phenomena was taken by natural philosophers such as Plato and Aristotle. They were less concerned with developing mathematical predictive models than with developing an explanation of the reasons for the motions of the Cosmos. In his Timaeus Plato described the universe as a spherical body divided into circles carrying the planets and governed according to harmonic intervals by a world soul. Aristotle, drawing on the mathematical model of Eudoxus, proposed that the universe was made of a complex system of concentric spheres, whose circular motions combined to carry the planets around the earth. This basic cosmological model prevailed, in various forms, until the sixteenth century AD.

Depending on the historian's viewpoint, the acme or corruption of physical Greek astronomy is seen with Ptolemy of Alexandria, who wrote the classic comprehensive presentation of geocentric astronomy, the Megale Syntaxis (Great Synthesis). Better known by its Arabic title Almagest, it had a lasting effect on astronomy up to the Renaissance. In this work, Ptolemy ventured into the realm of cosmology, developing a physical model of his geometric system, in a universe many times smaller than earlier (more realistic) conceptions It was not until the scholarly endeavours of Nicolaus Copernicus that astronomy developed much beyond this point. Copernicus was the first astronomer to propose a heliocentric system, in which the planets moved around the sun not the earth. His De revolutionibus provided a full mathematical discussion of his system, using the geometrical techniques that had been traditional in astronomy since before the time of Ptolemy. Copernicus’s work was later defended, expanded upon and modified by Galileo Galilei and Johannes Kepler.

Galileo is considered the father of observational astronomy. He was among the first to use a telescope to observe the sky, and after constructing a 20x refractor telescope he discovered the four largest moons of Jupiter in 1610. This was the first observation of satellites orbiting another planet. He also found that our Moon had craters and observed (and correctly explained) sunspots. Galileo argued that these observations supported the Copernican system and were, to some extent, incompatible with the model of the Earth at the centre of the universe. Kepler built on this work, and was one of the first scholars to unite physics and astronomy. Kepler was the first to attempt to derive mathematical predictions of celestial motions from assumed physical causes. Combining his physical insights with the unprecedentedly