The Greeks – around 500 BC – fuelled the first revolution. True – Chinese astronomers had been making meticulous observations of the sky for thousands of years: but they didn’t interpret them. The appearance in the sky of a ‘broom star’ (comet), or ‘guest star’ (supernova) meant only one thing: insurrection in the provinces. The Emperor had to be told at once.
On the other hand, the Greeks analysed what they saw in the sky. These philosopher-mathematicians were the first true scientists. Pythagoras pronounced that the Earth was a ball in space, around which everything moved in perfect circles; Aristarchus deduced that the relative sizes of the Earth and Moon, by looking at the shadow that our planet casts on the Moon during a lunar eclipse (and heretically taught that the Earth circled the Sun).
Eratosthenes managed to measure the circumference of the Earth, while Hipparchus charted the positions of nearly 1000 stars.
The Greeks even built the first computer – the Antikythera Mechanism – a clockwork dial which accurately predicted the positions of the Sun and Moon in the sky, along with eclipses.
They built up their vast repository of knowledge in the Great Library of Alexandria, in Egypt. It was in this city that Ptolemy (pictured right) flourished, as twilight began to fade on the great Greek Empire. He was a brilliant mathematician. In around AD 150, he collated all the Greek findings into a massive 13-volume treatise later known as its Arabic name of the Almagest (The Great Book).
After the demise of the Greek Empire, science went on hold. For 1400 years, the Arabian nations kept the flame alive in a lukewarm way. They referred to the Almagest: it was a means to tell the newly Islamic converts the direction of Mecca. The Arabs made accurate observations, and named many of the stars – but they didn’t question the Hellenistic theories. The Greeks had said it all.
With the Crusades, the Greek teachings were wrested out of Arab hands, and arrived in Europe. And – in the sixteenth century – the Polish canon Nicolaus Copernicus kickstarted the next revolution.
Copernicus (above) got his hands on some of the ancient records of predicted planetary positions; and – lo and behold! – the planets weren’t where they should be. He realised that things would be much better if it was assumed that the Earth travelled around the Sun, rather then vice-versa.
The scene was now set for astronomy to change forever. In 1609, Galileo Galilei turned his ‘optick tube’- the newly-invented telescope – towards the sky. Galileo made bold of his findings: that the Earth circled the Sun, and that the heavenly bodies were not perfect. The Moon was pocked with craters; and the Sun was spotty.
This was not good news for the Church authorities, who believed in the supremacy of a central Earth, and the purity of the Sun, Moon and planets. For his heresy, Galileo was placed under house arrest until he died. But his findings in astronomy and mechanics were to inspire a young Englishman, Isaac Newton, who was born in the year that Galileo died.
With his formidable mathematical brain, Newton worked out why bodies in space moved in the way they do: there was a new force to be reckoned with – gravity. At last, astronomers could calculate what was going on in the Universe, rather than just predict the future by what had happened in the past.
Now - armed with the power of the telescope, Newton’s laws, and dramatic strides in technology – astronomy was poised to surge forward. William Herschel doubled the size of the Solar System in 1781 when he discovered the planet Uranus; astronomers were at last able to measure distances to the stars; and – thanks to the labours of the German scientists Joseph von Fraunhofer, Robert Bunsen and Gustav Kirchhoff – they were able to ascertain their chemical make-up. Photography was a glorious spin-off of the new technology – it allowed observers to record their findings in perpetuity.
As the twentieth century hoved into view, the astronomical community was getting to grips with the structure of the Universe. Was our Galaxy all that existed? Or was it just one of billions? The latter proved to be the case; and – in one of the greatest discoveries of the last century, made by Edwin Hubble – our Universe is expanding.
And just over sixty years ago, the latest revolution in astronomy took off: one as great as that which happened in the era of Copernicus and Galileo.
