Ptolemaic system

We have come to think of progress in science as taking place through sharp changes in fundamental conceptions called scientific revolutions. The change need not be rapid, for the classic case of the scientific revolution encompasses nearly a century and a half between Copernicus and Newton. Unlike the example from astronomy, chemistry before its revolution in the eighteenth century had not found a theoretical structure at all comparable to the Ptolemaic system that had served astronomy so well and... 

The geocentric Ptolemaic system was superseded by the heliocentric system of Copernicus (1473-1543) principally owing to the work of Galileo, Kepler, and Newton in the seventeenth century. The planets are now known to revolve about the sun in elliptical orbits of small eccentricity at the following mean distances (in millions of miles)—Mercury, 36 . Venus, 67-2 Earth, 92-9 Mars, 141 5 Jupiter, 483 3 Saturn, 886 1 Uranus, 1783 Neptune, 2793 Pluto, 3666. 

No progress was possible until the defects in Aristotelean physics could be demonstrated experimentally and the discovery of the telescope showed up astronomical features at variance with the Ptolemaic system. This progress was too slow to cause an immediate paradigm shift and to break the unity of scientific astrophysics and astronomy on one hand, with astrology and... 

The cosmological model, which is generally known as the Ptolemaic system was formulated in the second century by Claudius Ptolemaeus in Alexandria. It was pubhshed in his 13-volume treatise, which became known to the Arabs as the Almagest, the name, meaning The Greatest, still used today. 

For a millenium, after the conversion of Constantine s mother, thinking in the western world was dominated by the spread of Christianity, orchestrated by the philosopher-saints, Augustinus and Thomas Aquinas. Their main concern was to align the Ptolemaic system, Aristotelian philosophy and the practice of astrology with their holy scriptures. 

Whereas the dogma of uniform circular motion demanded that the moving planet traverse equal arcs in equal intervals of time, Kepler discovered the new uniformity of equal areas in equal times to be valid for any elhpse, including the circle. By adding an additional focus to planetary orbits the need of epicycles was eliminated and the wandering planets were shown, for the first time, to follow harmonious paths around the sim. This discovery should have destroyed the Ptolemaic system for good. It failed. Not even Kepler s discovery of a new supernova, that remained visible for 17 months, was sufficient to shake the world s faith in a permanent sphere of fixed stars. 

There is an interesting parallel between the introduction of Newtonian mechanics and the introduction of Lavoisierian chemistry. As long as the planetary motions were only described, it was possible to evaluate all systems only on the basis of their accuracy of prediction. By this standard, the Ptolemaic and Copernican systems were not far apart and one might prefer... 

This addending of additional descriptors in order to salvage an existing system was akin to the system of Ptolemaic astronomy described in the footnote on page 123 in Chapter 3. 

In the early seventeenth century, Galileo s observations of the phases of Venus showed that the geocentric (Ptolemaic) model of the solar system was wrong and that the heliocentric (Copernican) model was correct. About a century later, Edmund Halley proposed that the distance from the Earth to the Sun (which was then unknown and is dehned as one astronomical unit, AU) could be measured by observing transits of Venus across the Sun. These transits... 

Chemistry at the beginning of the nineteenth century was in a position analogous to Ptolemaic astronomy. Around 100 C.E., Ptolemy created his astronomical system, which could be used to accurately chart the movement of all the visible planets, the sun, and the moon. His system worked perfectly well for navigation, time keeping, and all the other activities for which knowing the place of celestial objects was needed. Yet, Ptolemy s system had a philosophical problem. Each of the planets had its own system of movement, and the laws of planetary motion were different from those that governed motion on the Earth. Newton s astronomy and physics put all the planets, the stars, and motion here on Earth into a single system. 

Copernicus revived the correct theory of the system of the universe, which had been forgotten for so long, and eradicated it from anything that was repellent to sensory experience by means of the theory of apparent movements. He set up the extreme simplicity of real movements that results from this system in contrast to the almost fatuous complexity of those demanded by the Ptolemaic hypothesis. The movements of the planets were determined with greater accuracy, and Kepler s genius discovered the form of their orbits and the constant laws that regulate them. 

Copernlcan astronomy The system of astronomy that was proposed by the Polish astronomer Nicolaus Copernicus in his book De revolutionibus orbium coelestium, which was published in the month of his death (in 1543) and first seen by him on his deathbed. It used some elements of Ptolemaic astronomy, but rejected the notion, then current, that the earth was a staUonary body at the centre of the universe. Instead, Copernicus proposed the apparently unlikely concept that the sun was at the centre of the universe and that the earth travelled in a circular orbit about it. In addition Copernicus revived the idea that the movement of the sun and the fixed stars was due to the daily axial rotation of the earth. Galileo s attempts, some 70 years later, to convince the Catholic church that in spite of scriptural authority to the contrary, the Copemican system was correct, met with such stem resistance that De revolutionibus was placed on the church s list of forbidden books, where it remained until 1835. 

Copernican (heliocentric) tmiverse Gopernicus pubhshes De revolutionibus On the Revolutions of the Heavenly Spheres), in which he refutes geocentric Ptolemaic cosmology and proposes that the Sun, not Earth, lies at the center of the then-known universe (the solar system). 

G. Galileo. Dialogue Concerning the Two Chief World Systems Ptolemaic and Copemican. University of California Press Berkeley, CA, 1967. 

VTiat is required is a more fundamental explanation that allows one to deduce the length of the periods from first principles and not just the number of electrons that any shell can contain. Maybe this will require a deeper theory than present quantum mechanics. Just like the removal of Ptolemaic epicycles had to await the discovery of the heliocentric model of the solar system. I don t know what exactly is required. What 1 do know is that if we have eveiy right to go on asking such questions and requiring that the theory predict what has up to now been explained semi-empirically (Emerson, Explanation Scerri, Explanation ). 

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