In the fifth century BC, Socrates considered that all in creation was from the premise that the body was but a temporary refuge for the soul and that this persisted after death. Socrates has left no written record, which was to be passed on by a pupil later. Socrates for his beliefs was forced to commit suicide by drinking poison. Plato, the student of Socrates founded a school of ethics and metaphysics. Mathematics was derived from Pythagoras. Plato however observed the Universe and the planets. A student of Plato's, Eudoxus, observed the length of the year accurately and a theory that all the heavenly bodies moved around a circular orbit on a sphere somehow fixed to the earth. The sun and Moon and the planets each rotated around spheres. Yet Heracliedes, another pupil of Plato's suggested that Mercury and Venus circled the Sun.
Aristotle was a third pupil of Plato who later tutored Alexander the Great. Whilst Alexander was alive Aristotle's school was prominent. He wrote extensively about the natural world and attempted to formulate a set of laws. Only a modest proportion of his work survives. He classified all living things and wrote on philosophy. He proposed that matter was continuous and made of atoms or particles that filled all space. The atoms comprised the four elements of earth water air and fire that could be converted from one to another. The heavenly bodies were attached to crystal spheres that rotate uniformly around an axis upon the earth. The atmosphere of the earth included water air and fire. Beyond was the ether. All was created by God. Everything fabricated in its perfect circle. Space was finite but time unending. If a body was to be moved it had to be displaced by something else which applied a force proportional to the time of application of that force. Objects in motion reached a natural place of equilibrium.
After the Aristotelian school there was a centre in Macedonia founded by Alexander where Ptolemy founded big library that lasted for 500 years. Here Euclid formulated his geometry. Euclidian geometry was based upon a flat surface only. Archimedes in Sicily theorised on the principle of leverage and a law of force uon levers. The idea of the density of a body was apparently derived by him when lying in his bath and realising the displacement of the water by his own body. He derived a method to measure the area of curved surfaces which again as later with Newton and Liebnitz used approximations. Claudius Ptolemy 127 - 145 AD, produced the Almagest; thirteen books relating to astronomy and the motion of the planets in the sky. This includes the star catalogue of Hipparchus with 850 stars and Ptolemy had improved this to include 1022 stars. Again he considered the Universe to be spherical with a stationary earth in the centre. The earth was fixed and bodies fell to the centre of the earth. He argued that if the earth had rotated a body would not fall vertically back down but to the side away from the rotation. Thus the Sun and Moon rotated around an earth that was fixed. The movements of the planets were explained by epicycles.
Copernicus wrote a book called the revolutions of the Heavenly Orbs and proposed that the centre of the Universe was not the earth but a spot near to the sun. For the first time there was a heliocentric system with a stationary Sun and the planets in order around it. The motion of the Moon was then also explained but there wasn't an action of gravity. He realised that the stars were so far away that they appeared to be fixed.
Giordano Bruno was an Italian monk. His treatise was published in London. His ideas being that the earth moved around the sun and that the sun itself moved as well. The Universe was infinite. He was condemned to prison for seven years and burned to death in 1600.
Tycho Brahe was adopted by a rich uncle. He studied at Copenhagen but switched from law to astronomy. He found the planetary and stellar tables inaccurate and having inherited a fortune he built an observatory and found a new star. Given an island by Frederick the second to build a new Observatory he commenced a programme of measurement of the fixed stars. This was done without a telescope however 717 stars were measured with great accuracy. He left his data Kepler. Kepler was convinced that the movement of the planets must be a mathematical. He considered that the planets could be regarded as fitting into regular spheres but he abandoned his geometric model due to inaccuracy. Again he observed a new star and became famous. He at last realised that the motion of Mars can not be explained if the earth was at the centre. He described the movements of the planets for the first-time as elliptical. he noted that the speed of the planet in the elipse varied and also developed a theory of tides based on the attraction of the Moon. He noted that a planet speeds up close to the Sun and slows down when away from the sun. Therefore the force decreased with distance from the sun. He thought that the sun was magnetic. Yet he did not propose gravitation. He was a skilled astrologer yet continually sought evidence to confirm the role of the planets in his own life. He was introduced to be to the telescope and explained how this worked.
Da Vinci showed that the cannonball travelled along a curved path. Benedetti fixed two bodies of equal weight expecting them to fall faster. Then in 1586 Stevin showed that two load spheres of unequal weights took the same time to fall
Descartes built a theory of man and the universe and rejecting the senses he philosophised "I think, therefore I am." He advised criticism and scepticism and rechecking of reasoning. He described path of a moving object at any point intersecting two parallel lines at right angles and described by a list of positions and times. This he expressed in algebraic terms. He described a universe infinitely large, filled with infinitely divisible matter. The matter was set in motion by God and the matter imparted motion to any body within. The rotation of the sun was caused by the rotation of the matter in a whirlpool. Planets were carried round the sun in this vortex. Matter continued in motion unless affected by that around it. He proposed two laws of motion: if two bodies have equal mass and velocity before collision then they will be reflected by that collision and retain their speed. If two bodies have unequal masses then the lighter body will be reflected with a speed equal to that of the heavier body. This was unfortunately not verified. Cartesian theory however survived almost indefinitely but was at odds with Newtonian science.
Galileo used maths and physics together with experimentation. He experimented upon a pendulums and realised they could be used to keep time. His leaning Tower experiment is famous but it is not certain that it was actually carried out. He asserted that the vertical notion of a body could be described by weight alone. He observed that projectiles took the path of a parabola. He described free fall in uniform motion stating that the distance traversed by a moving body during any equal interval of time are themselves equal. Acceleration by a body was equal in speed during any equal interval of time. Galileo discovered much of the secrets of the Universe with the telescope and announced in 1609 and 1610 that he had observed mountains and craters on the moon and sea like regions, planets n disc shapes, and stars point like. Venus was seen in phases phases and Jupiter to have four moons. Stars were far more numerous than those seen by the naked eye. Galileo was arrested following publication of his dialogue and remained under house arrest until his death. He had described the movements of the earth and the sun in the same terms as had Copernicus. His last discovery was that of the diurnal and monthly libration of the Moon (it's wobble from side to side) just before he went blind. He believed in the circular orbit of the planets still though, rather than ellipses.
The idea of an apple falling on Newton’s head was popularised by Voltaire and encouraged it seems by Newton himself. Descartes Galileo and Huygens amongst others had already considered the forces that kept the earth in motion a around the sun with the other planets. Descartes in particular considered that this could only be mediated by an ether and similarly Huygens thought that without gravity any celestial body would never stop. Newton developed his calculus to describe the movements of the planets, but the forces and movement in an orbit is constantly changing and approximations are necessary to maintain the calculus. Gravitation was applied to show that in inverse square law related to circular and elliptical motion. Voltaire wrote in 1730, “A Frenchman who arrives in London will find philosophy like everything else very changed here. He left the world a plenum, and now he finds a vacuum” Newton still seemed to have in mind a plenum or ether filled space, since he said “that one body may act upon another at a distance through a vacuum without the mediation of anything else… is to me so great an absurdity that I believe no man who has in philosophical matters a competent faculty for thinking, can ever fall into it.”[1]
Robert Hooke however (1635 - 1703) had postulated before Newton the doctrine of universal gravitation, but was unable to express it mathematically. He did moreover state the inverse square law and related this to the path of projectiles. He quarrelled constantly with Newton on the basis of who introduced these ideas first. He had made many inventions including an odometer; a hearing aid; a reflecting Quadrant; a system of telegraphy; a barometer; the universal joint; and anchor escapement for clocks and an arithmetical machine (calculator). He produced the Gregorian telescope and a theory of the variation of the compass. He explained the scintillation of the stars by irregular atmospheric retractions and inferred the solar repellant force in producing the tails of comets. He suggested the motion of the sun amongst the stars and propounded correct notions as to the nature of fossils and the succession of living things upon the earth. Also a marine barometer. One of his posthumous works was an hypothesis of the cause of gravity found in any propagated pulse of the ether.
[1] The many faces of Mach, RH Dicke, Gravitation and Relativity. W.A.Benjamin, 1963, p.121.