A proficient mathematician, he tried to assess the relative distance of the Sun and the Moon from Earth, by measuring the angle between them when the Moon appears exactly as one quarter. The dominant view of the cosmos among scientists was geocentric, with the Earth being at the centre of the Universe and everything else revolving around it, but there were some who were edging closer to the truth.Īristarchus of Samos was one of the few supporters of the heliocentric system, identifying that the Earth travelled around the Sun rather than the other way around. Among other sciences, astronomy flourished at Alexandria, a Greek colony off the northern coast of Egypt, with a renowned library and museum. It was much later, in the third century BCE, that Greek astronomers first attempted to use astrometry to estimate cosmic scales. But they had no idea how far away the stars and the planets were. From this cradle of civilisation in Mesopotamia – in the southern part of present-day Iraq – astronomers had built up knowledge of the celestial bodies and recorded their periodic motions. The first documented records of systematic astronomical observations date back to the Assyro-Babylonians around 1000 BCE. Monitoring the motions of stars and planets in the sky was the best tool to track time, which was fundamental for agriculture, religious rituals and navigation. Credit: John GoldsmithĬuriosity alone did not inspire the earliest astronomers: astronomy and astrometry were practical sciences too. The Moon and comet Hale-Bopp over the Great Pyramids of Giza in 1997.

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