Cosmic Quest

There have been three great revolutions which have shaped our view of the heavens and our place in the Cosmos – and we are currently living through the turmoil of the third period of astronomical breakthrough.

I’m sure I speak for many others, in feeling incredibly privileged to be alive during through the current revolution, which started in the middle of the twentieth century. And it’s not just because I’m an astronomer. Throughout history, the firmament has had a driving influence on the development of humankind – and never more profound than when celestial revolutions take place.

Because the history of astronomy is far more than just the history of a science. It’s a reflection of our culture; an insight into our ideas, ideals, and beliefs. Why otherwise would we call the sky ‘heaven’, and populate it with our deities and cherished legends?

Revolution Number One: The Greek Geeks

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.

How did astronomers prove something so counter-intuitive as the idea that the Earth is on the move? Read on to find out more....