the Scientific Revival

In the chapter, ‘the rise of science’, in Bertrand Russell’s History of Western Philosophy it talks ultimately about Newton’s thoughts and findings on universal laws. But in order to understand Newton and his theories I have to understand all the early astronomers which caused the progression into his theories. These are the main points I have drawn from this chapter in order to understand how Isaac Newton came to his conclusion of universal gravitation.

The first Astronomer to take note of is Copernicus (1473-1542). Copernicus was a Polish ecclesiastic, but essentially hypothesised about astronomy. He came up with the initial idea that the sun is at the centre of the universe, and earth has a two-fold motion: a diurnal rotation and annual revolution about the sun. His most important book was called ‘De revolutionibus orbium coelestium’ and was published year of his death in 1543, this book displayed his hypothesis. His work can only be considered Pythagorean and not modern due to the fact that all celestial motions must be circular and uniform (not elliptical or having the ability to change direction). Also it had the absence of the stellar parallax, this meant that if the earth was 186,000,000 from the point it will be in six months, it will cause a shift in the apparent position of the stars. From this it can be assumed that he wasn’t aware of Aristarchus’s heliocentric theory. Despite being considered Pythagorean I believe that this was one of the first attempts to understand the universe through mechanics.

The second astronomer to note is Kepler (1571-1630). Now Kepler adopted the heliocentric theory and discovered three of the most important factors leading up to Newton’s findings. He discovered three laws of planetary motion, 2 of which were published in 1609, and the third in 1619. These laws where:

1)      Planets describe elliptic orbits, of which the sun occupies one focus

2)      The line joining a planet to the sun sweeps out equal areas in equal times

3)      The square of the period of revolution of a planet is proportional to the cube of its average distance from the sun

The striking thing about the first law is the change from the assumption which Copernicus held that planets orbit the sun in a circle motion. It was the first time that an elliptical orbit was mentioned. The second law essentially means that planets when orbiting speed up when nearer to the sun and slow down when further away. The third law explains how different planets all have their own movement patterns according to the equation.

The final Astronomer to consider before Newton which further expands on this knowledge is Galileo (1564-1642). Galileo was Italian and can be considered to be the founder of dynamics; he also adopted the heliocentric system. He discovered the importance of acceleration in dynamics. “Acceleration’ means change of velocity, whether in magnitude or direction; thus a body moving uniformly in a circle has at all times acceleration towards the centre of the circle.’ He also said that ‘everybody if left alone will continue to move in a straight line with uniform velocity; any change, whether in rapidity or direction of motion is done with ‘force’. This was enunciated by Newton as ‘the first law of motion’ or the law of inertia; it was the first idea of ‘force’ being able to change something’s ‘mechanical’ direction. He also established the law of falling bodies, which is; ‘When a body is falling freely, its acceleration is constant’ however ‘resistance of the air may interfere’ also ‘acceleration is same for all bodies, heavy or light, great or small.’

Sir Isaac Newton (1642-1727) was an English physicist, mathematician, astronomer and philosopher. He discovered that every planet, at every moment, has acceleration towards the sun which varies inversely as the square of the distance from the sun, acceleration towards the earth and sun. This explains the moons impact on the earth which is known as... Gravity! He described universal gravitation as a ‘force’ which is the cause of change of motion.

‘Everybody attracts every other with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them’ - Sir Isaac Newton.

From this theory he was able to deduce everything in planetary theory: the motions of the planets and their satellites, the orbits of comets, the tides and this essentially saw the change from medieval times to modernism, and a new wave of scientific theory and conclusions which we know today. His first law of motion deduced that lifeless matter, once set moving, will continue to move for ever unless stopped by some external cause the solar system, was kept going by its own momentum and its own laws. The earth was now seen as a minor insignificant planet opposed to the centre of the heavens as religion explained it, and a new sense of humanistic self-belief was incurred opposed to the self-hate which religion promoted.