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Early Astronomers

Updated on June 18, 2012

The distance around the Earth was first accurately by the Greek astronomer Eratosthenes measured (about 276 -194 BC). His calculations were based on the fact that at midday on midsummer day the Sun was directly above Aswan in Egypt-where it shone down a well without casting a shadow.

On the same day he measured the angle of the Sun at midday in Alexandria - where he was the Director of the Library - and compared it with that at Aswan, about 800km (500 miles) due south. He found that there was a difference in angle of one-fiftieth of a circle - about 7 degrees - between the two cities. So he deduced that the distance between and Aswan was about one-fiftieth of Alexandria the Earth's total circumference. His figure of about 40,000km (25.000 miles) almost matched the modern measurement of 40.007km (24,859 miles) for the Earth's circumference through the Poles.

Many of the findings of the Greek astronomer Ptolemy (about AD 120- 80) were based upon lies. That is the conclusion of a 20th-century American astronomer, Robert Russell Newton. who accuses Ptolemy of inventing bogus observations to support his theories. and of altering. for the same reason, genuine observations made by earlier astronomers. Ptolemy. who lived and worked in Alexandria.

Egypt. recorded his astronomical views in a 13-volume treatise. now known by its Arabic title as the Almagest, meaning 'The Greatest'. Newton bases his attack on close analysis of the treatise's contents. On one occasion. asserts Newton in his book The Crime of Claudius Ptolemy, published in 1978. Pto- lemy reported an impossible observation. He gave the time of a lunar eclipse that took place on September 22,200 BC, as the equivalent of 6.30pm. Yet the time could not have been observed directly because the Moon did not rise until half an hour later on that date.

To give the bogus observation credibility. Ptolemy attributed it to an earlier and widely respected Greek astronomer. Hipparchus, whose own records have long since vanished. And. since Hipparchus was thought by his contemporaries to be a man above suspicion. Newton is in no doubt about who did the faking. Far from being a genius. he insists. Ptolemy was a fraud.

The wealthy Danish astronomer Tycho Brahe (1546 -1601) had a large part of his nose sliced off during a sword fight and ordered a replacement made of gold. silver and wax. He had the nosepiece painted the colour of flesh. glued it in place and wore it until his death more than 30 years later at the age of 54.

He had fought a duel with a young nobleman over who was the better mathematician. Six years before the duel. at the age of 14, Tycho had intended to become a lawyer. But after witnessing a partial eclipse of the Sun on August 21. 1560, he determined to become an astronomer. His career took off in November 1572 when he observed a brilliant supernova - an exploding star-which was subsequently named Tycho's Star. It was the brightest known supernova seen for 1000 years and Tycho's description of it disproved the belief, dating back to the Greeks, that the heavens were unchanging.

Although the Italian astronomer Galileo Galilei (1564-1642) was the first person to train a telescope on the skies. he did not, it seems, invent the device himself. It is thought to have been invented by accident in 1608 by the children of a Dutch spectacle maker, Hans Lippershey. The children are said to have been playing one day in their father's workshop in the town of Middelburg and put together a concave spectacle lens and a short-focus convex lens.

Lippershey used the telescope, as he called it, to observe a distant weather vane, which looked larger and nearer. The following year Galileo heard of the telescope and made a more powerful model for himself in his studio in Padua. His observations, which led him to support Copernicus's revolutionary theories, were regarded as heresy by the Roman Catholic Church and Galileo was later put on trial for his life.

He was found guilty, but was spared after he recanted his heretical views. Galileo spent the last eight years of his life in exile near Florence. But although, to save his life, Galileo had denied his findings in public, he never recanted in private. And on his deathbed in 1642 he stated defiantly: 'Yet still it (the Earth) moves!'


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