## Astronomy: Copernicus, Kepler, Galileo, Newton, and Leibniz.

1543: 'The Revolution of Heavenly Orbs' - by Nicolaus Copernicus (1473-1543).
• The ancient Greek philosopher Pythagoras (Circa. 570-495 B.C) proved that the Earth was round and Aristarchus suggested that the Earth and Planets revolved around the Sun.

• However Ptolemy an Egyptian mathematician, astronomer, and geographer believed that the Planets and Stars revolved around the Earth. He wrote this about 100 A.D., and the church accepted this 'geocentric' theory as it placed the Earth at the centre of the Universe!

• Nicolaus Copernicus (1473-1543) a Polish astronomer studied the sky from the top of a Cathedral. In 1543 he wrote his book 'The Revolution of Heavenly Orbs'. Published by a Lutheran printer. In it he said the Earth revolves round the Sun once a year. Spinning on it's axis once a day. A 'heliocentric' theory. This upset the church who stuck with their view.

• Later the Danish astronomer Tycho Brahe (1546-1601) made careful measurements of 800 stars and the movement of Mars using an 'astrolabe'.

• His pupil, Johannes Kepler (1571-1630) a German astronomer and natural philosopher, took over his work. He discovered the Planets revolved in ellipses not circular orbits! Which further upset the Church. He is noted for formulating and verifying the three laws of planetary motion. These laws are now known as Kepler's laws:
1. Kepler's First Law: the planets orbit the sun in elliptical paths, with the sun at one focus of the ellipse.
2. Kepler's Second Law: the areas described in a planetary orbit by the straight line joining the centre of the planet and the centre of the sun are equal for equal time intervals; that is, the closer a planet comes to the sun, the more rapidly it moves.
3. Kepler's Third Law: states that the ratio of the cube of a planet's mean distance, d, from the sun to the square of its orbital period, t, is a constant—that is, d3/t2 is the same for all planets.

• Galileo Galilei (1564-1642) an Italian mathematician, scientist, and astronomer became one of the first people to build a telescope, using the new invention of lenses. By December 1609, Galileo had built a telescope of 20 times magnification. He observed the Milky way; lunar craters, mountains and valleys on the Moon; Sun spots; the phases of Venus; and the orbit of the inner planets in the solar system. He also observed the four largest satellites rotating around Jupiter, a completely separate planet. In physics, he discovered the laws of falling bodies and the motions of projectiles. In 1610 he wrote a book called 'The Starry Messenger' which proved Copernicus correct. This upset the Church further and his book was seized, and he was forced to recant. In 1624 Galileo began a book he wished to call 'Dialogue on the Tides' in which he discussed the Ptolemaic and Copernican hypotheses in relation to the physics of tides. Banned by the Church in 1630. He was put on trial in 1633 for "grave suspicion of heresy" and sentenced to house arrest for the rest of his live.

Galileo’s final book 'Discourses Concerning Two New Sciences' studying motion and the principles of mechanics was published at Leiden in 1638. The book opened a road that was to lead Newton to the law of universal gravitation that linked Kepler’s planetary laws with Galileo’s mathematical physics.

• Sir Isaac Newton (1642-1727) invented 'the Calculus' (or 'Fluxions' as he referred to it) in 1666 a mathematical method that allowed the movements of the planets to be mathematically predicted, it also has many other scientific and engineering uses. It was used by the Space Programme in to 20th Century to chart the trajectories of robotic probes across the solar system. His famous bit off propaganda about the 'apple falling' allegedly gave him the idea for Gravity. A force the pulled the apple down, and acted on planets, moons, comets, and the sun.
In 1667 he wrote the famous book 'Philosophiae Naturalis Principia Mathematica'. Some regard this as the start of the second great age of science. The first being the ancient Babylonians and Greeks. In it it states Newton's Three Laws of Motion:
1. "A object remains, at rest or continues in its motion, unless acted on by another force."
2. "The pull of an object (or Planet) is inversely squared to it distance."
3. "Every Force has a equal and opposite reaction."

Lucasian Chair (1669-1702) of Mathematics at Cambridge University; President of the Royal [Scientific] Society, London (1703-1727); Member of the Parliament (1689-90, 1701) of England; Warden of the Royal Mint (1696-1699); Master of the Royal Mint (1699-1702) a post for which he was Knighted (1705) by Queen Anne.

• The Royal Society was chartered by King Charles II in 1660 who was very much interested in Science.
• Other professors to hold the Lucasian Chair include the early computing pioneer Charles Babbage (1828-39); and theoretical physicist Stephen Hawkings (1980-date) who wrote 'A Brief History of Time' among other things, and can calculate complex Mathematical Equations in his head.
• Parliament used to actually have one M.P. each from Oxford and Cambridge Universities.

• It should be noted that Baron Gottfried Wilhelm Leibniz (1646-1716) a German philosopher, mathematician, and statesman independently invented 'the Calculus' in 1675. Also known as 'Infinitesimal Calculus' as it manages to mathematically model differentials or integrals for infinitely small steps between numbers. Leibniz's system was published in 1684, Newton's in 1687, and the method of notation devised by Leibniz was universally adopted. In 1672 he also invented a calculating machine capable of multiplying, dividing, and extracting square roots, and he is considered a pioneer in the development of mathematical logic.