Since prehistoric times our ancestors gazed up towards the celestial heavens and observed the movements of the Sun, Moon and stars. Not surprisingly, astronomy is probably the oldest science known to man and over the passing centuries our understanding of the Universe has developed gradually to reach the considerable level of knowledge we possess today. What follows are some key dates in the timeline of astronomy:
32,500+ BCE: During the Upper Paleolithic period, early people would keep track of the Moon‘s phases by engraving lines onto animal bones, and it has also been suggested that they might similarly have memorialized certain star patterns in the same way. One famous example includes a small piece of a mammoth tusk discovered in the Ach Valley in Germany dated between 32,500 and 38,000 years old which is purported to depict the constellation of Orion.
10,000+ BCE: To early humans, the sky was where the gods dwelt and so early priests were holy men who interpreted their divine will through a careful study of astronomy mixed with religion. Astronomy was also an important component of human life, as it could be used as a method to predict the cycle of the seasons for agricultural purposes, as well as for measuring time and direction. This became especially important with the advent of the Agricultural Revolution during the Mesolithic to Neolithic period around 12,500 years ago.
4,900 BCE: The Goseck Circle in Germany, consisting of four concentric circles, a mound and two wooden stakes, is believed to be the world’s earliest Sun observatory enabling ancient people to accurately measure its path during the course of a solar year.
2,000-3,000 BCE: During this period in Mesopotamia, the constellations of Leo, Taurus, Scorpius, Gemini, Capricorn, and Sagittarius were invented, with these zodiac constellations also marking the path of the Sun, Moon, and planets throughout the year. The earliest astronomical records and star catalogs were kept by the Sumerians, then Babylonians, with the earliest known clay tablets recording the position of the planets, and solar eclipses dating to around 1600 BCE.
2,500 BCE: The prehistoric monument of Stonehenge in Wiltshire, England, was a sacred place of worship and is aligned to mark the summer and winter solstices.
2,137 BCE: Chinese record earliest known solar eclipse.
1,450 BCE: The Egyptians start to use sundials.
800 BCE: Indian astronomer Yajnavalkya proposes a heliocentric concept of the universe in which the Earth is spherical and the Sun is at “the centre of the spheres.”
600 to 130 BCE: Greeks first to develop astronomy from being an observational science related to religion into a theoretical science about the structure of the universe. Pioneers during this period include Pythagoras, Thales, Plato and Aristotle who proposed a geocentric model of the Universe with the Sun circling the Earth.
450 BCE: Greek philosopher Anaxagoras suggest that the stars are actually suns, similar to our own, but located at such vast distances that we are unable to feel their heat back on Earth. His theory attracted disapproval from religious groups, though, and he was subsequently exiled from Athens.
280 BCE: Greek astronomer Aristrachus of Samos suggests a heliocentric theory of the universe, whereby it was the Earth and planets which revolved around a stationary Sun. However, his theory was not popular and it would be nearly 1800 years before it would finally be accepted.
150 A.D: Ptolemy further refined the original geocentric model in his masterpiece ‘Almagest,’ which listed 48 constellations, and chartered the motions of the stars and planets.
1543 A.D: During the Renaissance period modern astronomy began to take shape when Copernicus published his “De Revolutionibus Orbium Coelestium” which used empirical evidence to revive Aristrachus’ heliocentric view of the Universe,
1576 A.D: Tycho Brahe compiles accurate and comprehensive observations on the positions of the planets to further credit the Copernican system over the Ptolemaic one.
1605 A.D: Johannes Kepler discovered that the planets orbit about the Sun in an elliptical and not circular motion, and so proposed his three laws of planetary motion.
1608 A.D: Dutch spectacles maker Hans Lippershey invents a refractor telescope.
1609 A.D: Galileo used 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. Galileo’s attempts to defend the heliocentric model of the universe landed him in direct conflict with the powerful church. In 1632 he was tried for heresy, forced to recant and condemned to spend the rest of his life under house arrest.
1668 A.D: Sir Isaac Newton invented the first reflecting telescope which used a curved mirror instead of a lens to look further into space. Newton later publishes his hugely influential book called ‘Philosophiae Naturalis Principia Mathematica’ in which he agrees that the Earth rotates around the Sun and explains the reasons behind Kepler’s three laws. He also establishes the law of universal gravitation, which ushered in a new Age of physics and Enlightenment.
1798 A.D: Laplace proposes the concept of Black Holes.
1905 A.D: Albert Einstein introduces special Theory of Relativity then in 1916 his general Theory of Relativity.
1937 A.D: First radio telescope built in the USA by Grote Reber.
1957 A.D: Russian Sputnik 1 satellite becomes the first man-made object to orbit the Earth marking the beginning of the space age.
1969 A.D: Neil Armstrong and Buzz Aldrin walk on the Moon as part of the Apollo 11 mission.
1990 A.D: The Hubble Space Telescope (HST) is put into orbit from space shuttle Discovery. The 2.4m aperture reflecting telescope continues to circle the Earth taking extremely sharp images of outer space.
1992 A.D: Radio astronomer Wolszczan and Frail announce the discovery of the first definitive detection of exoplanets. Over the intervening years hundreds of planets outside of our solar system have now been confirmed.
See also: History of Astronomy