Early astronomers already make the distinction between stars and planets, as the former remain relatively fixed for centuries, while the latter wander an appreciable amount in a comparatively short time. But that’s not all!
Greece, 3rd century BC, Aristarchus of Samos gets the credit for being among the first ones to suggest a heliocentric model. Yet, his heliocentric world view appears outlandish, because it seems so counter-intuitive.
Hipparchus of Nicea measures the Earth precession and compiles a stellar catalogue in the 2nd century BC. Eratosthenes uses the angles of shadows created at wide intervals, and manages to estimate the circumference of the Earth with great accuracy.
The Antikythera Mechanism
The Antikythera mechanism, an ancient observational device for calculating the celestial movements of the Sun, the Moon, and possibly the planets, dates back from about 150-100 BC. Believed to be the first analogue ancestor of an astronomical computer, it is famous for its use of a differential gear. The miniaturisation and intricate complexity of its parts make it comparable to an 18th century clock.
Living in a Geocentric World
Despite such early advances in knowledge, Ptolemy (90-168 AD) writes the Almagest and his model of a geocentric universe has a lasting effect on the world of astronomy.
His vision endures for centuries…
Until in 1543, Copernicus publishes On the Revolutions of Celestial Spheres (De revolutionibus orbium coelestium) shortly before his death. A century before Newton arrives on the scene, Copernicus begins rejecting the prevalent world view of the Earth-centred Universe, in favour of a renaissance of the early Greek’s heliocentric view of the Earth orbiting around the Sun.
In 1600, Giordano Bruno (1548-1600) does not escape the fires of Roman Inquisition.
While in 1633, Galileo Galilei (1564-1642) is “invited” by the authorities of the Catholic Church to renounce supporting a belief he based on his own experimental observations.
Eppur si muove!
Johannes Kepler (1571-1630) is in the right place at the right time, comparatively speaking. XVIIth century northern Europe is mostly Protestant leaving him free to formulate his ideas that the planets do revolve around the Sun, in agreement with the best observational data he has available.
1609, Kepler publishes his Astronomia Nova. His discoveries are underpinned by the newest of ideas, such as Descartes (1596-1650) and the realisation that geometry problems can be reformulated as algebra problems: his coordinate geometry provides scientists with new ways of tackling the conundrums that baffled the greatest scientific minds of Ancient Greece.
Isaac Isaac Newton (1642-1727) goes on to establish a convincing quantitative framework for scientific knowledge. He publishes his Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), widely regarded as one of the most important works of Science, where he presents his definitions of mass and force. At the heart of Newton’s world view is a belief that all motion around us may be explained by a set of three simple laws of motion…