Physics Evolution - Text Only Version
1700 to 1840
During this time, revolutions in America and France affected the cultural outlook of these (and other) nations. Invention and experimentation became respectable and natural philosophy was quickly developing into physics in the wake of its first heroes from The Renaissance.
Benjamin Franklin , experimenter/inventor – Invented bifocals and shocking kite (1706 to 1790)
American inventor born in Boston, America.
Benjamin Franklin was a newspaper editor, diplomat, philosopher and inventor. He ran away from his tyrannical brother when he was seventeen and ended up in Philadelphia. There he set up a print shop and, eventually, bought his own newspaper.
Franklin’s publishing business thrived and he could indulge his interest in science, carrying out the famous (and dangerous) kite experiment. He hung a key on the end of a kite’s string and flew the kite into a thundercloud whilst wearing a silk glove for protection!. His experiment showed that lightning was a kind of electricity. The next two people to try this experiment were electrocuted!
He explained static electricity as a single fluid that could appear both positive and negative. As a businessman, he made an analogy with a bank account that can be in the black or in the red. Before him, people thought that there were two types of static electricity.
He also invented bifocals, the odometer, the Lightning Rod and the Franklin stove, for which he didn’t take out a patent because he felt the device was for public good.
In 1757, he travelled to England to represent Pennsylvania (then an English colony) in its battle with the Penn family. Although at the time he was a loyal (English) subject, his views changed whilst he was in England and by 1776 he was helping to draw up the Declaration of Independence and the Constitution of the United States.
- Franklin built on Von Guericke’s ideas on electricity
- Volta worked on electricity at about the same time as Franklin.
- Coulomb developed electrical ideas at about the same time as Franklin.
- Faraday was born the year after Franklin died and combined electrical ideas with magnetism.
- Henry combined theories on electricity with magnetism.
Count Alessandro Volta, physicist – Invented the voltaic pile (1745 to 1827)
Physicist born in Como, Italy
Alessandro Volta is known for his pioneering work in electricity.
In 1775 he devised the electrophorus, an instrument that produced static electricity by friction. Stimulated by Luigi Galvani’s discovery of animal electricity in 1786, Volta piled up little discs made from different metals in a salt solution to produce a continuous flow of electricity. By 1800 he had developed the so-called voltaic pile, a forerunner of the electric battery.
Galvani and Volta disagreed passionately about whether the electricities they produced were the same. Galvani held that his animal electricity was different from Volta’s electricity and Volta believed they were the same – as we do now.
In honour of his work in the field of electricity, Napoleon made him a count in 1801.
The electrical unit, the volt was named after him.
Volta picked up ideas and electrostatic techniques from Von Guericke
Volta was inspired by Galvani’s work but disagreed with his ideas.
- Faraday took forward many of Volta’s early ideas on electricity.
- Ohm developed some of Volta’s ideas.
- Henry combined Volta’s electrical ideas with magnetism.
Luigi Galvani, physiologist- Famous for twitching frogs (1737 to 1798)
Physiologist, born in Bologna, Italy
Luigi Galvani is noted for his studies of the effects of electricity on animal nerves and muscles. He discovered, accidentally, that two different metals could produce what he called ‘animal electricity’. It may be that he elaborated the accidental aspect of the discovery to make a better story.
However, the story is that he was doing some experiments on dissected frogs’ legs – making them twitch using static electricity (or ‘artifical electricity’ as he called it). During an experiment, his assistant (probably his wife) touched a nerve with a metal scalpel while a frog’s leg was hanging on a brass hook.
These findings led Volta to the invention of the voltaic pile, the world’s first battery. Galvani’s name is still associated with electricity in the words galvanometer, galvanism and galvanization.
- Galvani used static electricity generators like those of Von Guericke
- Volta was inspired by Galvani’s work but they disputed the interpretations
Marquis Pierre de Laplace, mathematician – Kept his head for nebular theories (1749 to 1827)
Astronomer and mathematician, born in Normandy, France.
Pierre de Laplace’s deftness and pragmatic politics meant he was spared during the Reign of Terror which claimed, amongst many others, Lavoisier.
In 1796, he published Exposition du systeme du monde in which he proposed a nebular theory for the formation of the Sun and Earth – i.e. that a cloud of matter contracted to form the stars and planets. His general idea is still accepted today.
Later he published methods that used differential equations and probability theory to apply Newton’s theory of gravitation to explain planetary motion.
Laplace called himself the ‘French Newton’ and it is his model of the Universe rather than Newton’s that we usually associate with Newton. Newton’s Universe required God’s intervention (through comets); whereas Laplace’s did not. Napolean, on seeing his description accused Laplace of eliminating God from the Universe. “Sire” he replied “I have no need of that hypothesis”.
- Laplace called himself the ‘French Newton’ and worked with many of his ideas
- Like Descartes, Laplace had a theory of a clockwork Universe
- Laplace helped bring the calculus of Leibniz into mainstream mathematics
- Foucault was the next great French mathematician
Charles Coulomb, physicist – Did he really get those results? (1736 to 1806)
Physicist, born in Angoulème, France.
Charles Coulomb is another French experimenter and man of science who survived the Reign of Terror. Afterwards, he was summoned to Paris and helped to devise the metric system of weights and measures.
He invented the torsion balance for measuring the small forces between electrically charged particles and magnetic poles. With this invention, he was able to formulate Coulomb’s law, describing the force between electric charges. His law is remarkably similar to Newton’s law of gravitation and he was strongly influenced by Newton’s work.
Given the difficulty in obtaining accurate results – even with his torsion balance – it is likely that he knew what he was looking for when he began the experiment. He may even have cheated a bit!
The unit of electrical charge, the coulomb, was named after him
- Coulomb used machines like Von Guericke’s to generate static electricity
- Coulomb would have worked with the other French physicists like Volta
- Coulomb developed some of Franklin’s ideas on electricity
John Dalton, chemist – A teacher at 12 years old (1766 to 1844)
Chemist born in Eaglesfield, Cumberland (now Cumbria), England
John Dalton is best known for his contributions to atomic theory but he also identified the phenomenon of colour blindness, an affliction that he shared with his brother. He was a prodigy and became a teacher at his local school when he was just 12.
In his New System of Chemical Philosophy (1808), he proposed the idea of tiny particles or atoms which could not be created or destroyed. He also developed the techniques of atomic weights and formulae.
Many of his ideas were widely taken up, although many scientists rejected his notion that matter was made up of hard, indivisible atoms.
Gradually, like most scientific innovations, atomism became generally accepted.
- Dalton’s atomic theory was very close to an ancient one proposed by Al Razi
- The Greek philosopher Democritus had given us early ideas on atoms
- At one time Dalton taught James Joule and his ideas on atoms were key to the statistics of Kelvin and Maxwell
André Ampère, physicist – Forces on electric currents (1775 to 1836)
Physicist and mathematician born in Polemieux-au-Mont-d’Or, France
Ampère is best known for his contributions to the study of electrodynamics and electromagnetism. In 1826, he proposed Ampère’s law which describes mathematically the magnetic force between two electric currents.
He performed many experiments that allowed him to explain known electromagnetic effects and predict new ones as well.
He invented a galvanometer, an instrument that uses a freely moving needle for detecting and measuring electric currents.
The ampere (amp), the unit of electric current, is named after him.
- Ampère’s theories on current relied on Coulomb’s charges
- Ampère developed ideas on current flow Volta
- Ampère and Ohm were aware of each other’s work
- Faraday picked up many of Ampère’s ideas on currents and magnetic fields
- Joseph Henry developed Ampère’s ideas on magnetic fields and currents
- Ampère’s law is one of the laws that Maxwell formalised into his famous equations
Heinrich Olber, astronomer – Olber’s paradox on starlight (1758 to 1840)
German astronomer born in Abergen (now part of Bremen).
Heinrich Olber discovered several comets and asteroids. He devised a method, still employed by astronomers, for calculating the orbits of comets.
In 1826, he wrote an important paper on a problem that had been noted by previous thinkers, namely why the sky is dark at night. The essence of the puzzle is that if the universe were infinitely big and full of stars, then in every direction we look the line of sight should end on a star, and the whole sky would be uniformly illuminated.
This observation, called Olber’s paradox, has been resolved with the discovery that the observable universe has only a limited extent – probably no greater than 20 billion light years’ radius.
- Olber used methods of Newton and Halley to calculate orbits
- Olber took forward Laplace’s ideas on the Universe
- It was the work of Edwin Hubble that finally helped resolve Olber’s paradox
Georg Ohm, physicist – Liked the good life and gave us Ohm’s Law (1787 to 1854)
German physicist, born in Erlangen,
Georg Ohm learnt his science and mathematics from his self-taught father, Johann. When he finally went to school (or Gymnasium), there was little in the way of inspiration or science.
He went to university but his father removed him after a year because Georg used the opportunity to carouse rather than learn. He took up a teaching job and, now more mature and a little chastened, continued his own research and reading.
Ohm is best known for his work on electric currents. He defined electrical resistance in the relationship V=IR and gave his name to the unit of electrical resistance (which has to use the Greek symbol omega as an ‘O’ would be very confusing!).
- Ohm developed the work of Volta
- Ohm and Ampère were familiar with each others’ work
- Faraday and Ohm were working in the same field
- Kirchoff used Ohm’s equation to derive his own laws on circuits
Michael Faraday, physicist – Working class boy made good (1791 to 1867)
Physicist born in Newington, Surrey.
Michael Faraday was an apprentice bookbinder and the son of a blacksmith and although he received little formal education, in 1812 he obtained a job as a scientific assistant to Sir Humphry Davy at the Royal Institution.
He had been inspired by the book Conversations on Chemistry by Jane Marcet and started going to Davy’s lectures. In turn, he wrote them into a book which he bound by hand and presented to Davy. Davy was so impressed that he gave him a job at the Royal Institution.
In 1831 Faraday and the American Joseph Henry independently discovered the phenomenon of electromagnetic induction now known as Faraday’s Law.
In 1845 Faraday discovered the magnetic rotation of light (Faraday rotation) and speculated that light might be electromagnetic in nature. He thought it might be transverse vibrations of his field lines. He also suggested that light and electricity may be different manifestations of the same force.
He investigated the phenomena of electrolysis and developed the laws of electrolysis.
He is credited with building the first electrical transformer and the electric dynamo. His work led directly to the development of electrical machinery for industry.
- Faraday developed and relied on the work of Ampère
- Lenz formalised and refined Faraday’s ideas on electromagnetic induction
- Faraday and Ohm would have been familiar with each others’ work
- Henry independently discovered the same laws of electromagnetic induction but failed to publish them
- Faraday would have relied on work by Volta on electricity
- Maxwell’s equations take in Faraday’s law on electromagnetic induction
Joseph Henry, physicist – Tried watchmaking, acting, teaching and… (1797 to 1878)
Physicist, born in Albany, New York.
Joseph Henry was a reserved and quiet man from an ordinary background – his father was a New York labourer. At thirteen, he became a watchmaker’s apprentice and, as a young man, almost became an actor. However, friends persuaded him to take a place at the Albany Academy.
Whilst he was a schoolteacher, he discovered the principle of electromagnetic induction – before the British physicist Michael Faraday. But Faraday published his findings first and is credited with the discovery. However, Henry also deduced the idea of self inductance and gave his name to its unit.
In 1831, Henry constructed the first practical electromagnetic telegraph and devised and constructed one of the first electric motors. His ideas led directly to the work of Morse and Bell in telecommunications.
- Henry developed and relied on the work of Ampère
- Lenz formalised some of Henry’s ideas on electromagnetic induction
- Henry’s ideas on inductance took Ohm’s theories to a higher level
- Henry independently discovered the same law as Faraday but failed to publish before him
- Volta’s work would have been the basis of much of Henry’s own
Heinrich Lenz, physicist – World traveller and physicist (1804 to 1865)
Russian physicist born in Dorpat (now Tartu) Estonia
Heinrich Lenz had travelled the world by the time he formulated his law. He was a geophysicist who had been on a three year trip around the globe when he took up a post at St Petersberg.
Here Lenz studied electromagnetism and induction and devised his law for determining the direction of Faraday’s induced currents. Lenz also studied the heating effects of an electric current and, independently of English physicist James Joule, came up with the law now known as Joule’s law.
- Lenz formalised the ideas of Farady’s law
- Lenz developed Henry’s ideas along with those of Faraday
- Maxwell included Lenz’s law into his famous set of equations
Gustav Kirchhoff, physicist – Ruined his eyesight for his work (1824 to 1887)
German physicist born in Konigsberg (now Kaliningrad) Russia.
Gustav Kirchoff suffered for his science by staring for too long at the Sun.
With the German chemist Robert Bunsen, Kirchhoff developed the modern spectroscope for chemical analysis. He used it to examine the Sun’s spectrum, identifying its dark spectral lines – but also ruining his eyesight. Bunsen had a safer time discovering the elements caesium and rubidium in 1860.
Kirchhoff showed that alternating currents (or signals) in wires are carried at the speed of light. This was one of the theories picked up by Maxwell in the 1890s.
He is mainly remembered for his laws on black body radiation and, for those who like simultaneous equations, his laws for analysing circuits.