19-07-2008 Great astronomers: Copernicus. (Article 146)

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Simon Kenny
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19-07-2008 Great astronomers: Copernicus. (Article 146)

Post by Simon Kenny » Wed Dec 31, 2008 10:25 am

Great astronomers: Copernicus. (Article 146)

Born in the Polish town of Torun, beside the Vistula, in February, 1473, Micolaj Kopernik, or Nicolas Copernicus is seen by many as the father of modern astronomy. He belonged to a wealthy, influential merchant class, with family connections in church and business affairs. His background enabled him to get the best education Europe had then to offer at Bologna, Padua and Ferrara. Ironically, the astronomical revolution he inspired was the result of work he did in his spare time. Most of his life was spent multi-tasking as economist, canon lawyer, diplomat, governor and military advisor.

While studying medicine at Ferrara, Copernicus came across old writings describing ancient theories about Earth’s movement in space. He decided to study these and confirm a suspicion forming in his mind: that the Sun, not the Earth, is the centre of the then known universe, i.e. the Solar System.

Up to Copernicus’s time, the universe was believed to be ‘geocentric’, that is the Earth is the centre of the cosmos, round which everything else, including the Sun, revolved. Popularised by the Greek mathematician, Ptolemy, in the second century AD, this theory fitted well with the religious belief that humans are at the centre of God’s creation. Copernicus was about to deal a hard blow to human vanity!

The ‘heliocentric’ or Sun-centred theory did not begin with Copernicus. In fact, it was proposed in Indian texts dating back to the eight century BC. The Greek philosopher, Aristarchus also proposed the idea with other Greek thinkers in the second century BC. It was the thoughts of these Greek philosophers, related in the writings of Plato and Cicero, which inspired Copernicus to develop the heliocentric theory. What was different in this case was that Copernicus subjected the theory to scientific investigation for the first time. The result of his study, spanning nearly 30 years, was his master-work, ‘De Revolutionibus Orbium Coelestium’, (On the Revolution of Heavenly Spheres). It was finally published just before his death in 1543.

In ‘De Revolutionibus’, Copernicus proposed the universe is divided into eight spheres, two of which are motionless: one containing the Sun at the centre and the other, the eighth, at the outside of the cosmos, containing the unmoving stars. The other six spheres carried the then known planets, Mercury, Venus, Earth, Mars, Jupiter, and Saturn. He also correctly attributed the daily motion of the Sun and stars across the sky to the earth’s axial rotation. Copernicus held the popular belief that the planets motions were circular. Around 1605, Johannes Kepler refined Copernicus’s theory when he discovered that planetary motion was elliptical.

Copernicus’s revolutionary theory of the universe was published too late in his life to embroil him in controversy with Church authorities. He insisted it was only a theory, and dedicated his work to Pope Pius III, perhaps to forestall controversy. The confrontation was to wait until 1616, and Galileo Galilei.

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