Physics Evolution - Text Only Version

1400 to 1680

The Renaissance - or rebirth - began in Italy and saw the ideas of The Greeks returning to Europe. The message spread northwards and explorers spread west to cover the globe. Within 300 years through religious and civil conflicts, natural philosophers had rewritten the Ancient foundations and tools of philosophy.

Leonardo da Vinci, Renaissance man- Left handed mirror writer! (1452 to 1519)

Renaissance man born in Florence

In his lifetime, Leonardo da Vinci was primarily an artist, living off commissions and patronage from the rich and powerful. However, he was also an inventive designer- though none of his 'inventions' was ever built. In the fields of anatomy, optics and hydraulics, he anticipated many of the developments of modern science - he even designed a workable flying machine.

His scientific theories, like his artistic innovations, were based on careful observation and precise documentation. His notebooks were written in mirror script - either to keep them secret or because he was left handed.

This may have contributed to the fact that no-one really knew of his findings in his own lifetime; had they been published, they would have been of great interest to engineers and designers in the 16th and following centuries.

Nikolas Kopernig (Copernicus), astronomer – Did he change the Universe? (1473 to 1543)

Astronomer born in Thorn (now Torun), Poland.

Nikolas Kopernig – usually known by his Latin writing name, Nicolaus Copernicus – is best known for his heliocentric theory of the Universe. This updated and, eventually, replaced Ptolemy’s ideas, which were showing their age (they had lasted for about 1500 years – not bad as theories go).

In his work On the Revolutions of the Celestial Spheres, Copernicus proposed that the Sun is at the centre of the Universe; the planets, including the earth, revolve around it.

However, this defied the teachings of the Church and his books were heavily censored or even banned by the Vatican.

Nevertheless, most astronomers still used his techniques – but only as a means of calculating planetary positions and not as a representation of reality. For this, they stuck with the church-approved views of Aristotle. It was another 100 years before astronomers began to accept his ideas as true.

Tycho Brahe, astronomer – Why did he have a metal nose? (1546 to 1601)

Danish astronomer, born in Knudstrup in southern Sweden (then part of Denmark).

Tycho Brahe is (and was) famous for his comprehensive astronomical measurements. His data exceeded all the existing astronomical measurements and were only bettered by the invention of the telescope early in the 17th century. They were vital for the work of Kepler.

However, he was also well known as an eccentric and a tyrant. As a child, he was kidnapped by his Uncle (after his father reneged on a promise to hand over his first born if it was a boy). As a young man he had part of his nose cut off in a duel following an argument over who was the better mathematician; he wore a metal nose for the rest of his life (it may have been silver or brass). And, as an older man, having been given an island (and its inhabitants) by the King of Denmark, he abused his tenants mercilessly.

Tycho’s observations of the new star of 1572 and comet of 1577, proved that these bodies were above the Moon and that the planets could not be carried on Aristotle’s spherical shells because comets would have to move through these spheres.

Sophia Brahe, Danish astronomer and historian – A legend in her own lifetime (1556 to 1643)

Sophia was the younger sister of Tycho Brahe and assisted him with his astronomical observations. Sophia made her own career as a horticulturist, healer, historian and astronomer. Like Tycho, she became a legend in her own lifetime. Even today, some European universities use her chronicles as an exemplar of methodology in research techniques.

Galileo Galilei, mathematician and astronomer – Was he a hero or a heretic? (1564 to 1642)

Mathematician and astronomer born in Pisa, Italy.

In 1609 Galileo built a telescope and looked into the sky. With it, he was able to observe mountains and craters on the Moon, the moons of Jupiter, and the phases of Venus.

Although telescopes were already being used, he was the first person to point it at the heavens – which were still thought as being separate and more ordered from the Earth. Previously, telescopes were used for terrestrial activities like navigation, communication and controlling ships in harbour.

In his Dialogue Concerning the Two Chief World Systems, Galileo attacked Greek cosmology and defended the Copernican system with the Sun at the centre of the solar system.

Galileo was condemned by the Catholic Church for his views which were considered heresy. He was tried by the Inquisition and sentenced to spend the last years of his life under house arrest.

Much is made of his run in with the Catholic Church and the fact that the Vatican took until 1993 to officially recognise the validity of his work. However, it is most likely that he fell foul of local politics with cardinals rather than being in direct conflict with the Church. Indeed, Jesuit priests were carrying out experiments through the 16th and 17th centuries.

He made experimentation fashionable and, by dropping objects from the Leaning Tower of Pisa, showed that objects fall at the same rate. His work on the periods of pendulums – inspired by a swinging chandelier in the cathedral – were another example of how experimentation could reveal new ideas. He also conducted thought experiments about forces and dynamics and his work was to influence Isaac Newton, who was born in the year of his death.

William Gilbert, natural philosopher and doctor – What is the angle of dip? (1544 to 1603)

English natural philosopher and doctor born in Colchester, England.

William Gilbert was a natural philosopher and physician – to Elizabeth I, no less. We remember him primarily for his experiments into the nature of magnetism.

Although compasses had been used for many centuries, no-one understood how they worked. Some thought it was an attraction to the Pole star; others thought that the North Pole was home to a mysterious range of iron capped mountains that would rip the nails out of any ship that ventured too close. There was even a theory that garlic affected compasses – which meant that helmsmen were forbidden from eating it.

Anyway, Gilbert showed that a compass swings north because the Earth is a giant magnet. Also, based on the work of Robert Norman – a compass maker – he showed that a compass needle pointed downwards as well as northwards. We now know this as the dip of the Earth’s field – although the idea of a field is much more recent.

He also believed that the planets were held in orbit by magnetic forces – an idea that Kepler followed as well.

Gilbert was the first to use the terms electric force, electric attraction and magnetic pole.

Johannes Kepler, German astronomer – Laws of planetary motion (1571 to 1630)

Astronomer and natural philosopher, born in Weil-der-Stadt, Germany.

Johannes Kepler, a contemporary of Galileo, corresponded with and. for a short time, worked for the astronomer Tycho Brahe.

Unlike Brahe, Kepler accepted the Copernican (Sun-centered) theory of the Universe. He used Brahe’s extensive and precise data to show that the orbits of the planets are not circles but “flattened circles” or ellipses.

His three laws became very well established and a yardstick by which future theories would be judged. Isaac Newton relied heavily on them to validate his inverse square law of gravity.

René Descartes, French philosopher and mathematician – Scientific reason and x,y co-ordinates (1596 to 1650)

Philosopher and mathematician born in La Haye, France.

Descartes is often called the father of modern science. His revolutionary Discourse on Method proposes the use of reason to search for the truth.

He rejected all ideas based on assumptions or emotions and even removed his own existence from what could be assumed. However, given that he was able to think about whether or not he existed, he deduced that he must. Hence his statement “Cogito ergo sum” – I think, therefore I am.

He proposed the idea of a clockwork Universe: having been set in motion by God, everything follows mechanical laws and the Universe unwinds fatalistically like a clockwork toy. Unlike Newton, Descartes didn’t accept that forces could act without contact; so his Universe is full – everything is touching something else – sometimes via an ether, though his ether was different from Newton’s.

From his name, we get the adjective cartesian. This describes the system of x,y,z axes and positions (Cartesian coordinates) and the diving balloon in a sealed jar of water (Cartesian diver).

It also describes his followers, the Cartesians, who (like the Newtonians later) had a long running dispute with Leibniz. In this case about motion and force (what we call momentum).

Otto von Guericke, German natural philosopher – Pressures, vacuums and static electricity generator (1602 to 1686)

Natural philosopher born in Magdeburg.

Like many well known experimenters of his day, Otto von Guericke had the good fortune to be born into an aristocratic family and therefore have the time and funding to follow his scientific interests.

In 1672, von Guericke developed the first generator that could produce an electric charge. He also invented an air pump. With this he stunned an audience by making the Magdeburg hemispheres that could not be pulled apart by two teams of eight horses.

The hemispheres showed the strength of atmospheric pressure and also that it was not impossible to create a vacuum – a view that had been held up to then by, for example, Descartes and Aristotle.

Robert Hooke, English natural philosopher – Elastic properties, astronomy and light theory (1635 to 1703)

Natural philosopher born on the Isle of Wight

Robert Hooke was an architect and surveyor for the City of London after the Great Fire. He was also an extremely accomplished natural philosopher who had wide ranging experimental skills and invented many instruments.

There are those who, probably fairly, think that Hooke had a raw deal in life and in posterity. In his day, he was prolific and accomplished, yet he is remembered mostly for just the one law (on elasticity) and his feud with Newton.

Hooke was born 7 years before Newton on the Isle of Wight and was orphaned at 13 when his father hanged himself. By then, he had also survived smallpox, which had left him badly disfigured. Later, there were those, including his niece (with whom he was besotted and had an affair), who avoided him because he was so ugly.

Being seven years older than Newton, he was well established at the Royal Society by the time Newton submitted his paper on light. Hooke opposed Newton’s ideas and the animosity between the two men continued on and off until Hooke’s death 24 years before Newton. By then, Newton was President of the Royal Society and was able to promote his own side of their feud at Hooke’s expense.

Isaac Newton, English mathematician and natural philosopher – Laws of motion, gravitation and theories on light and calculus (1642 to 1727)

Mathematician and natural philosopher, born in Woolsthorpe, Lincolnshire

Isaac Newton was born in the year that Galileo died and is often seen as his successor. He had a colossal intellect and, in his early adulthood, an unstoppable drive to understand everything.

Newton’s working life has two distinct halves – as a reclusive, eccentric, academic in Cambridge and as a wealthy, influential and famous philosopher in London. He had long running feuds with Leibniz and Hooke. The first was over who had been the first to develop the methods of calculus; the second was over all sorts of things – it probably started when Hooke objected to a paper Newton wrote on light.

His greatest works – Opticks and Philosophiae naturalis principia mathematica – originated from his time at Cambridge. The ‘Principia’ is the masterwork that provided, in a mathematical way, the framework for understanding forces and motion. As well as containing his laws of motion it took, for the first time, physics into the heavens with his universal law of gravitation. Previously, the celestial arena had been thought of having separate laws from those on Earth. It was Newton who proposed that the same force (gravity) holds the Moon in orbit and us on the ground.

According to legend, Newton began thinking about universal gravitation when he saw an apple fall from a tree in his Lincolnshire orchard – where he had returned to avoid the plague in Cambridge. On returning to Cambridge in 1666, he developed pages of notes on the subject but didn’t show anyone. Nearly 20 years later, Halley visited Newton after a bet with Hooke over who could derive Kepler’s laws from a law of gravitation. Newton gave Halley the answer and the proof almost instantly.

Halley persuaded Newton to publish his findings. He even paid for the publication after the Royal Society withdrew funds. Principia was first published in 1687.

Nine years later, after some nervous breakdowns, Newton moved to London and spent the last 28 years of his life as Master of the Mint. He lived comfortably and well and, as President of the Royal Society, strongly influenced further research.

Gottfried von Leibniz, German mathematician – Developed calculus and other mathematical methods (1646 to 1716 )

Mathematician and philosopher born in Leipzig, Germany.

He developed (independently from Isaac Newton) a new kind of mathematics known as calculus. However, there was (and is) a long running dispute over who was the first to come up with the ideas. The two men exchanged a number of letters that vary in tone but, even when polite, show the distrust between them.

He made original contributions to optics, mechanics, statistics, logic, and probability theory and conceived the idea of calculating machines.

Whoever got there first, it is Leibniz’s methods that we use today. Newton claimed that he wrote the ‘Principia’ using his calculus and converted this to geometry so as to publish it in the language of The Ancients. So, despite its huge influence, the ‘Principia’ did not bring calculus into natural philosophy. On the other hand, the German mathematician Leonhard Euler developed Leibniz’s calculus which then spread to France about a hundred years later. It arrived in the UK in the early 1800s.

Edmond Halley, English astronomer and mathematician – Halley’s comet and work in magnetism (1656 to 1742)

Astronomer and mathematician born in London.

Edmond Halley went to University in Oxford and worked with Robert Hooke and Christopher Wren. It was Wren who challenged the other two men to explain elliptical orbits from a law of gravitation. Halley, possibly becoming fed up with Hooke’s boasting, visited Newton in Cambridge to ask his advice.

However, as well as being the instigator and funder of Newton’s Principia, Halley made many contributions of his own. He published many articles and produced the first meteorological map that showed prevailing winds around the world.

His magnetic theories – which included the ideas of the Earth having a moving inner core and wandering poles – were important for well over a hundred years.

He showed that some comets have elliptical orbits and that the comets seen in 1531, 1607 and 1682 were in fact the same one. It is now known as Halley’s comet, although he was not the first to see it.