Ancient civilizations believed their gods lived in the skies, and so early astronomy was often a mix of detailed observations of the celestial heavens and religion. As well as a method of trying to divine the will of the gods, astronomy also allowed for more practical applications, such as predicting the cycle of the seasons for farming, measuring time and as a directional compass.
By 5000 BCE, ancient peoples had started constructing sun observatories, such as the Neolithic Era ‘Goseck circle’, to accurately measure the heavens. The Sumerians and Babylonians then kep some of the earliest astronomical records yet found, containing lists of bright stars, names of various constellations, and the movement of the planets Mercury, Venus, Mars, Jupiter and Saturn.
By 3,000 BCE the Egyptians had a fairly accurate calendar with the year divided into 365 days, or 12 ‘months’ of 30 days and an extra five days added on at the end of the year as feast days. Other parts of the world, too, were carefully studying the heavens and in 2137 BC the Chinese recorded the earliest known solar eclipse.
Nevertheless, astronomy still remained closely tied to astrology and it wasn’t until 600 BCE onwards that Greeks such as Pythagoras, Thales of Miletus, Plato, and Aristotle helped turn astronomy from mere observation to being a theoretical science concerned with the structure of the universe. They also used mathematics, geometry and trigonometry to help explain the reasons for the motions of the Cosmos. Despite Aristrachus of Samos in 280 BCE then suggesting the first heliocentric theory whereby it was the Earth and planets which revolved around a stationary Sun at the center of the Universe, his theory was not generally accepted and Ptolemy further refined the accepted geocentric model in his 140 A.D masterpiece ‘Almagest,’ which was used by the western world for the next 1500 years.
Modern astronomy began to take shape during the time of The Renaissance, despite fierce protestations by the Church. In 1543, Copernicus published his “De Revolutionibus Orbium Coelestium” which used empirical evidence to support a heliocentric view of the Universe, while Tycho Brahe compiled detailed observations on the positions of the planets. In around 1605, four years after Brahe’s death, his assistant and successor Johannes Kepler observed that the planets moved in elliptical orbits around the Sun, and so proposed his three laws of planetary motion.
Galileo then added to the growing body of scientific astronomy data by using the newly invented telescope to make some incredible astronomical observations, including viewing Jupiter‘s rotating moon system, and noting there were obviously objects in the heavens which didn’t revolve around the Earth. By 1687, Sir Isaac Newton invented a new telescope that used a curved mirror instead of a lens to look further into space, and published his hugely influential book called ‘Philosophiae Naturalis Principia Mathematica.’ Newton agreed that the Earth rotated around the Sun and also established the law of universal gravitation, which ushered in a new Age of physics and Enlightenment.
Since then mankind has done a pretty thorough job mapping the stars, planets and their moons, and compiling a whole catalog of astronomical objects and predicting their nature. In 1798 for instance, Laplace proposed the concept of Black Holes, and by 1817 Charles Messier had compiled a list of 103 deep sky objects he identified as not comets, and which included nebulae, star clusters, and galaxies.
Astrophysics received a major boost in 1900 when Max Planck invented quantum mechanics and Einstein’s two theories of Special and General Relativity changed the way we viewed the structure of space-time and gravity forever.
By the mid-1900’s Edwin Hubble had proved that galaxies were separate systems outside of our own Milky Way and that the Universe was expanding. Mankind has now walked on the moon, established Space Stations in orbit around the Earth and discovered hundreds of planets outside of our solar system.
See also: Important Dates In The Timeline Of Astronomy