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1840 to 1890

This was the age of steam ships, trains and machinery. International trade increased and there was an incentive to understand and improve the technologies of the age. Scientists (as they were now called) felt that they would soon be able to understand all of nature.

James Joule, Physicist born in Salford, Lancashire, England (1818 to 1889)

Took his work on honeymoon.

As the son of a wealthy brewery owner, James Joule and his brothers were privately tutored - at one time by John Dalton.

When James and his brother took over the family brewery, he set up a laboratory at home. He was a devout Christian and believed that an understanding of nature would bring him closer to his God.

He investigated the heating effects of an electric current and was determined to show that things could also be heated through mechanical work. He eventually succeeded using some water paddles that repeatedly raised and dropped the water.

However, on his honeymoon, he failed to measure a temperature difference between the top and bottom of the waterfall at Chamonix.

His work on electrical and mechanical heating effects led to the theory of conservation of energy - the First Law of Thermodynamics. The unit of energy, the joule, is named after him.

Together with the physicist William Thomson (later Baron Kelvin), Joule found that gases cool when they expand - the principle behind the refrigerator.

As a schoolboy, Joule was taught by John Dalton.
Joule developed ideas on electrical heating based on work by Ohm and others.
Joule worked with Lord Kelvin on theories about heating.

Jean Foucault, Physicist, born in Paris (1819 to 1868)

Invented the gyroscope.

Jean Foucault was famous for working on the effects of the rotating Earth, inventing the gyroscope. In 1851 he gave a spectacular demonstration to show the Earth's rotation by suspending a pendulum on a long wire from the dome of the Pantheon in Paris.

He worked with the French physicist Armand Fizeau in measuring the speed of light in air and water.

Foucault would have studied the work of his French predecessor Laplace
Michelson was the next to develop theories on the movement of the Earth.

William Thomson (Baron Kelvin), Mathematician and physicist born in Belfast, Ireland (1824 to 1907)

A prodigy who spanned two centuries.

From the age of 10, William Thomson (later Baron Kelvin of Largs) attended Glasgow University, where his father was chair of mathematics. When he was 16, he went to Cambridge and by the age of 24 had proposed the absolute scale of temperature that still bears his (lordly) name.

Like many of his contemporaries, Thomson thought that Physics was more or less a complete science. In his words: "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement."

As well as his hugely important theoretical work, Thomson invented a marine compass and a boosting device that allowed telegrams to be sent across oceans.

Dalton's theory of atoms was essential to Kelvin's work on thermodynamics.
Kelvin worked with Joule on the ideas of heating and work.
Maxwell used Kelvin's ideas in his statistical analysis of temperature.

James Clerk Maxwell, Mathematician and physicist born in Edinburgh, Scotland (1831 to 1879)

Prodigious inventor who marked end of epoch.

James Clerk Maxwell was a prodigious scientist and investigator. Apparently, at the age of three, he constantly repeated "Show me how it doos".

By the age of 14, he had written a paper on ellipses and curves that was read to the Royal Society of Edinburgh.

His greatest work was to fundamentally change our view of reality, so much so that Albert Einstein said, "One scientific epoch ended and another began with James Clerk Maxwell". This was the expression of all the existing laws of electromagnetism in four differential equations.

These exemplify the holy grail of Physics - a self consistent, powerful theory that can be written in four lines of mathematics.

This theory predicted the existence of electromagnetic waves and provided the tools to create the technological age, from radio to mobile phones.

Maxwell relied on Dalton's atomic theory for his statistics and Faraday's law for his set of equations.
Kelvin's work on temperature was essential for Maxwell's statistical analysis.
Maxwell developed Joule's ideas on energy in a statistical way.
Hertz developed Maxwell's equations into a practical demonstration of radio waves.
Preserving Maxwell's equations was a measure of the success of Lorentz's transforms - used by Einstein.
When Bose made an error using Maxwell's statistics, he developed a whole new class of particle with its own statistics.

Thomas Edison, Inventor born in Milan, Ohio (1847 to 1931)

Light bulb, gramophone and electric chair.

Although he attended school for only three months, Thomas Edison patented more than 1,000 inventions including the light bulb, the fuse and the Edison battery. Invention and inventors were held in higher esteem in the USA than in Europe, where pure science was admired more.

Edison saw himself as the all American businessmen and entrepreneur. His drive to be top dog led, in 1890, to the first (and one of the most prolonged) killings in an electric chair.

The story started 12 years earlier when Nicola Tesla came to work for Edison. Gradually the men's personalities and adherence to direct (Edison) and alternating (Tesla) currents drove them apart.

Edison, with his d.c. systems, was determined to discredit a.c.. He arranged for a convicted axe murderer to be put to death by electrocution - using a.c., of course. The sentence was carried out in an 'electric chair' in August 1890. Then Edison's propagandists got to work - they used slogans like "Would you like your wife to be cooking with a.c.?".

His legacies - vacuum tubes, electric lights, the gramophone and the electric chair - live on.

Edison followed in Franklin's tradition of American inventor.
Edison developed Faraday's theories into practical applications.
Edison had a long running feud with Tesla.

Albert Michelson, Polish American physicist born in Strelno (now Strzelno, Poland) (1852 to 1931)

Astounding ethereal result.

In 1887 Albert Michelson, funded by Alexander Graham Bell, inventor of the telephone, developed the interferometer. Together with the American chemist Edward Morley he used the interferometer to measure the speed of light with great precision.

At that time, most scientists believed that light travelled as waves through the ether, a substance that filled the universe. They also believed that the Earth travelled through the ether. The Michelson-Morley experiment measured the Earth's velocity through the ether, and found it to be zero. This proved that the ether does not exist! (By now, the ether was very different from those of Descartes and Newton).

Eight years later, Einstein's Special Theory of Relativity explained this surprising result, giving weight to his revolutionary theory.

Michelson's result on the speed of light was key to Einstein's theories of Relativity.
Michelson's results showed that there wasn't an ether - as thought by Descartes and others.
Michelson developed ideas on the motion of the Earth from those of Foucault
With Maxwell's equations, Michelson's work led to the idea of electromagnetic waves in free space.

Nikola Tesla, Serbian American electrical engineer and inventor born in Smiljan (1856 to 1943)

Alternating battles with Edison.

Nikola Tesla was an electrical engineer, a poet and an inventor with a sharp and detailed imagination. He grew up and studied in Serbia but, having conceived the idea of an a.c. induction motor, headed for America in 1884. He arrived with four cents and a few poems in his pocket and was employed, for a brief period, by Thomas Edison.

The two men had very different outlooks and soon parted on unfriendly terms. Edison sold his patents for an a.c. system to Thomas Westinghouse.

In 1893, Tesla and Edison competed to supply Niagara Falls with hydroelectric power generators. Tesla's system won because Edison's direct current system was unable to distribute power efficiently for more than a few miles. By now, Edison had used his infamous electric chair to try to discredit Tesla's a.c. systems.

Tesla also worked with radio-frequency electromagnetic waves, and despite the claims made by Marconi, actually did invent the idea of radio as we know it today. When Tesla died in 1943 he held over 700 patents.

Tesla's work on a.c. relied on Faraday's law
Tesla developed ideas on inductance and coils from the work of Joseph Henry
Tesla and Hertz both worked with alternating currents and waves.
Tesla had a long running feud with Edison.

Heinrich Hertz, Physicist, born in Hamburg (1857 to 1894)

Died young but still gave us radio waves.

Heinrich Hertz was a talented Physicist who may have gone on to even greater things had he not died young.

He adapted Maxwell's Equations in the light of Michelson's early experiments (that showed that there probably wasn't an ether). He made the equations more symmetrical.

He demonstrated that electromagnetic radio waves (predicted by Maxwell) could travel through the air. His experiments (well before Marconi) led to the development of the wireless telegraph and radio.

The unit of frequency, one cycle per second, was named the hertz (Hz) after him.

Like Tesla, Hertz worked with a.c. and waves.
Hertz used Maxwell's equations to predict and produce electromagnetic waves.
The speed of light and electromagnetic waves were a part of Einstein's theories of relativity.
Hallwachs was one of Hertz's pupils.

Wilhelm Hallwachs, Physicist, born in Darmstadt, Germany (1859 to 1922 )

Strange experiment which Einstein explained later.

Hallwachs was a pupil of Heinrich Hertz. He noticed that shining ultra violet radiation on some metals allowed them to discharge an electroscope.

This property, the photoelectric effect, could not be explained at the time. It needed to wait for J. J. Thomson to discover the electron and then for Albert Einstein to put his mind to it in the early 1900s.

Today the photoelectric effect is used in many devices including light detectors and solar cells.

Hallwachs was a pupil of Hertz
Einstein explained Hallwachs' photoelectric effect in one of his three famous papers of 1905.
J J Thomson's discovery of the electron helped explain the photoelectric effect.

Dmitri Mendeleev, Russian chemist, born in Tobolsk, Siberia (1834 to 1907)

Political activist and table maker.

Dmitri Mendeleev was the youngest of fourteen children. Although his father died when he was young, his mother was determined to give him a good education and get him to University. She went with him to Moscow and then St Petersberg, where he was admitted with a scholarship to become a science teacher.

As a teacher and chemist, he became well known throughout Russia and, despite being politically outspoken, he was tolerated by the Tsar and the authorities.

His lasting achievement was the creation of the Periodic Table of elements. Before this, the only real knowledge about elements was their atomic mass. By grouping the 62 known elements according to their properties (in increasing atomic mass), Mendeleev was able to predict the existence of unknown elements.

His table established the idea that there was some underlying order within atoms that produced the regularity in the properties. This would lead atomic and nuclear physicists to try to understand what caused this.

Mendeleev built his table around the idea of atoms from the earlier work of John Dalton
J J Thomson and Rutherford relied on Mendeleev's work to think about the structure of atoms.
Bohr's model of the atoms relied on Mendeleev's ideas of periodicity.