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Physics is defined as dealing with the laws, properties and interaction of matter and energy, which by its very definition embraces a whole circle of sciences. The appended map illustrates the many branches of physics as tributaries which combine to swell the river of knowledge.

The following pages name a relatively small, but representative, number of scientists who in their own field, contributed to the overall knowledge of physics. In a world of ignorance and superstitious dogma, many risked ridicule and even death in their quest to secure the smallest step towards truth.

Not all were great inventors, to many it became their lifetime’s work just to prove a theory on which others could progress. Faced only with observation, calculation, and their own enquiring minds, they strove to explain the mysteries of natural phenomenon, and in so doing arrived at surprising discoveries. They established natural laws which govern our planet, and provided the measuring stick on which today’s scientific research is built.

Derek Cornforth
2001

ALHAZEN Ibn al Haytham c.965-1038. Arabian scientist, author of Kitah al Manazir/Book of Optics, translated into Latin as Perspective. For centuries it remained the most comprehensive and authoritative treatment of optics in both East and West.

AMPERE Andre Marie 1775-1836. French physicist. A child prodigy, he was a proficient mathematician by the age of twelve. He went on to make many discoveries in electro- magnetism and electrodynamics. He followed up the work of Hans Oersted on the interaction between magnets and electric currents, developing a rule for determining the direction of a magnetic field associated with an electric current. The ampere, usually shortened to amp, a unit of electric current was named after him.

ANAXGORUS, 500-428 bc. Greek natural philosopher. Born near Smyrna, he lived in Athens where he was a friend of Perciles, (490-429), the Athenian politician who saved him from death when Anaxgorus was charged with impiety and treason.

ANAXIMANDER, c.610-546 bc. Greek Astronomer and philosopher. He claimed that the Earth was a cylinder three times wider than it is deep, motionless at the centre of the Universe, and he is credited with drawing the first geographical map. He said that the celestial bodies were fire seen through holes in the hollow rim of wheels encircling the Earth. According to Anaximander, the first animals came into being from moisture, and the first human beings grew inside fish, emerging once fully developed.

ANDREWS John, 1813-1885. Irish chemist who conducted a series of experiments on the behaviour of carbon dioxide under varying temperature and pressure. In 1869 he introduced the idea of critical temperature -30.9C in the case of carbon dioxide, beyond which no amount of pressure would liquefy the gas.

ARCHIMEDES, c.287-212 bc. Greek mathematician who made major discoveries in geometry, hydrostatics, and mechanics. He formulated a law of fluid displacement, (Archimedes principle), and is credited with the invention of the Archimedes screw, a cylindrical device for raising water.

He was born at Syracuse in Sicily. It is alleged that the Archimedes’ principle of buoyancy was discovered when he stepped into the public bath and saw the water overflow. He was so delighted that he rushed home naked, crying, “Eureka! Eureka! (I have found it). He used his discovery to prove that the goldsmith of the king of Syracuse had adulterated a gold crown with silver. Archimedes designed engines of war for the defence of Syracuse, and was killed when the Romans besieged the town.

ARISTARCHUS of Samos. 280-264 bc. Greek astronomer. The first to argue that the Earth moved around the Sun, and was ridiculed for his beliefs.

ARISTOTLE, 384-322 bc. Greek philosopher who advocated reason and moderation. Born in Stagira in Thrace, he studied in Athens under Plato, and became tutor to Alexander the Great. In 335 bc, he opened a school in the Lyceum (grove sacred to Apollo) in Athens, as a community for research. Of Aristotle’s works some 22 treatises survive, dealing with logic, metaphysics, biology, psychology, ethics, politics and literary criticism. In his works of ethics and politics, he suggested that human happiness consisted of living in conformity with nature.

BACON Roger, 1214-1292. English philosopher and scientist born in Somerset and educated at Oxford and in Paris. He became a Franciscan monk and was in Paris until about 1251 lecturing on Aristotle. In 1266, at the invitation of Pope Clement IV, he began his Opus Majus/Great Work, a compendium of all branches of knowledge. In 1277 Bacon was condemned and imprisoned by the church for ‘certain novelties’ (heresy) and not released until 1292. He was interested in alchemy, biological and physical sciences and magic. Many discoveries have been accredited to him including the magnifying lens. He foresaw the extensive use of gunpowder, mechanical cars, boats and ‘planes.

BECQUEREL Antoine Henri. 1852-1908. French scientist who discovered penetrating radiation coming from uranium salts, the first indication of radio-activity. Uranium, the heaviest of all chemical elements, gave forth rays which could penetrate thin sheets of metal and leave their mark on a photographic plate. He shared the Nobel Prize with Marie and Pierre Curie in 1903.

BELL Alexander Graham, 1847-1922. Scottish scientist born in Edinburgh. He went to America in 1870. Inventor of the telephone, he gave his first successful transmission of sound by means of the telephone, which he patented in 1876. He originated the Bell Telephone Company in 1877. Establishing a laboratory, he produced the first successful phonograph record. He also invented the photophone, a device that transmitted sound on a beam of light, and devoted much of his time to the education of the deaf. In aeronautics, he invented the tricycle undercarriage.

He became professor at the University of Boston; Regent of the Smithsonian Institute in 1898, and was awarded the Volta Prize by the French government. He was also granted the Hughes Medal by the Royal Society.

BERNOULLI. Swiss family that produced many mathematicians and scientists in the 18th and 19th centuries, in particular the brothers Jakob (1654-1705) and Johann (1667-1748). Both were pioneers of Leibnitz’s calculus.

Jakob used calculus to study the forms of many curves arising in practical situations, and studied mathematical probability. Bernoulli numbers are named after him.

Johann developed exponential calculus and contributed to many areas of applied mathematics including the problem of a particle moving in a gravitational field. His son, Daniel (1700-1782) worked on calculus and probability, and in physics proposed Bernoulli’s principle, which states that the pressure of a moving fluid decreases the faster it flows. (Which explains the origin of lift on the aerofloil of an aircraft’s wing.) This and other work on hydrodynamics was published in ‘Hydrodynamica’ in 1738.

BOHR, Niels Henrik David, 1886-1962. Danish physicist. His theoretical work produced a new model of atomic structure, now called the ‘Bohr’ model, and helped establish the validity of quantum theory. After working with Ernest Rutherford at Manchester, he became professor at Copenhagan in 1916, and founded there the Institute of Theoretical Physics of which he became Director in 1920. Bohr fled from the Nazis in World War II and took part in work on the Atomic bomb in the USA. In 1952, he helped set up the European Nuclear Research Organisation (CERN) in Geneva. He was awarded the Nobel Prize for Physics in 1922, and his son Aage Bohr shared the Prize in 1975 for his work on atomic theory.

BOYLE, Robert, 1627-1691. Irish physicist and chemist who published the seminal ‘The Sceptical Chemist’ in 1661. He was the first chemist to collect a sample of gas, and formulated ‘Boyle’s Law’ on the compressibility of gas in 1662. (i.e. when the temperature of a gas remains constant, its volume varies inversely with its pressure.). He was one of the founders of the Royal Society, and endowed the Boyle Lectures for the defence of Christianity.

BRADLEY, James, 1693-1762. English astronomer who in 1728 discovered aberration (deviation from normal) of starlight. From the amount of aberration in star positions, he was able to calculate the speed of light. In 1748, he announced the discovery of nutation, i.e. variation in the Earth’s axial tilt.

BRAGG, (Sir) William Henry, 1862-1942. British physicist born in Cumberland. He was professor of physics at Adelaide (1886); Leeds (1909), and the University of London from 1915. In 1915 he shared with his son William Lawrence Bragg (1890-1971) the Nobel Prize for Physics for their research work on X-Rays, radioactivity, and crystals. He was knighted in 1920 and received the Order of Merit for his work. He wrote, ‘The World of Sound’, the ‘Universe of Light’, (1923) and others.

BRAHE, Tycho, 1546-1601. Danish astronomer of noble birth. In 1576 Frederick II of Denmark gave him the island of Hven in the Sound, together with a pension. Here he erected the observatory of Uraniborg. He made accurate observations of the planets from which the German astronomer and mathematician Johann Kelper proved that planets orbit the Sun in ellipses. His (Brahe) discovery and report of the 1572 supernova brought him recognition, and his observations of the Comet in 1577 proved that it had moved in an orbit among the planets, thus disproving the Greek view that Comets were in the Earth’s atmosphere. On the king’s death, he quarrelled with the authorities and eventually settled near Prague at the invitation of Kaiser Rudolph II where Kepler became his assistant.

BROGLIE, Louis Victor, Duke de 1892-1987. French theoretical physicist. He established that all atomic particles can be described either by particle equations or by wave equations, thus laying the foundation of wave mechanics. He was awarded the Nobel Prize for Physics in 1929.

CARNOT, Nicholas Leonard Sadi, 1796-1832. French scientist and military engineer who founded the science of thermodynamics. His pioneering work was ‘Reflections sur la puissance motrice du fen/On the Motive Power of Fire’. He died at the age of 36 a victim of the cholera epidemic.

CAVENDISH, Henry, 1731-1810. English physicist. A grandson of the second duke of Devonshire, he devoted his life to scientific pursuits living in rigorous seclusion at Clapham Common. He discovered Hydrogen (which he called ‘inflammable air’) in 1766, and he determined the compositions of water and of nitric acid. The ‘Cavendish experiment’ entailed the measurement of gravitational attraction between lead and gold spheres, which enabled Cavendish to calculate a mean value for the mass and density of the Earth using Newton’s Law of universal gravitation.

CELSIUS, Anders, 1701-1744. Distinguished Swedish astronomer born at Upsala, and became professor of astronomy there. He devised the Celsius scale in 1742 – the reverse of the centigrade scale, the freezing point of water being 100 degrees and the boiling point at 0 degrees at standard atmospheric pressure. The centigrade scale (100 boiling and 0 freezing) was officially renamed the Celsius scale in 1948 in order to avoid confusion with the angular measure known as the centigrade which is one-hundredth of a grade.

CHLADNI, Ernst Florens Friedrick, 1756-1827. German physicist known as the ‘Father of acoustics’. He conducted vital experiments with sound patterns of vibrating plates.

CLAUSIUS, Rudolph Julius Emanuel, 1822-1888. German physicist, one of the founders of the science of thermodynamics. In 1850 he enunciated its second law – heat cannot pass from a cooler to a hotter body.

COPERNICUS, Nicolaus, 1473-1543. Polish astronomer who believed that the Sun not the Earth is at the centre of the solar system, thus defying the church doctrine of the time. For thirty years he worked on the hypothesis that the rotation and the orbital motion of the Earth were responsible for the apparent movement of the heavenly bodies.

Born at Torun on the Vistula, then under the Polish king, he studied at Krakow and in Italy, and lectured on astronomy in Rome. On his return to Pomerania in 1506, he became physician to his uncle the bishop of Ermland, and was made a canon at Frauenberg, although he did not take holy orders.

COULOMB, Charles Auguste de, 1735-1806. French scientist, born in Angouleme. He invented the torsion balance for measuring the force of electric and magnetic attraction. The name Coulomb was given to the practical unit of quantity which is conveyed by one Ampere in one second.

CROOKES, William, 1832-1919. English scientist whose many chemical and physical discoveries included the metallic element Thallium in 1861, the Radiometer in 1875, and the Crookes’ high vacuum tube now used in X-Ray techniques. Crookes suggested that cathode rays consisted of something the discovery of which Faraday had long ago foreshadowed – matter in a fourth state neither solid, liquid nor gaseous, but radiant matter.

CURIE, Marie, (born Sklodovska). 1867-1934. Polish scientist who investigated radioactivity with her husband Pierre (1859-1906). Born in Warsaw she studied in Paris from 1891. Impressed by the publication of Becquerel’s experiments, Marie Curie decided to investigate the nature of uranium rays. In 1898 she reported the possible existence of a new, powerfully radioactive element in pitchblend ores. Her husband abandoned his own researches to assist her, and in the same year they announced the existence of polonium (named after her native country) and radium. They isolated the pure elements in 1902.

Both scientists refused to take out a patent on their discoveries and were jointly awarded the Davy Medal in 1903 and the Nobel Prize for Physics in the same year with Becquerel. In 1904 Pierre was appointed to a chair in Physics at the Sorbonne, and on his untimely death in a street accident, was succeeded by his wife. She wrote a treatise on Radioactivity in 1910, and was awarded the Nobel Prize for Chemistry in 1911. She took no precautions against radioactivity and died a victim of radiation poisoning. Her notebooks, even today, are too contaminated to handle.

The Curie’s first daughter Irene Joliot-Curie worked with her mother at the Radium Institute in 1935 and she and her husband Jean-Frederic were awarded the Nobel Prize, (Chemistry, 1935), for their discovery of artificial radiation.

d’ALEMBERT, Jean le Rond, 1717-1783. Notable French mathematician and encyclopedist. He was associated with Diderot in planning the Great Encyclopedie. Diderot, (1713-1784) the French philosopher, was closely associated with the European movement for intellectual, social and scientific progress.

DAVISSON, Clinton Joseph, 1881-1958. American physicist. With Lester Germer (1896-1971), he discovered that electrons undergo diffraction, so proving Louis de Broglie’s theory that electrons, and therefore all matter, can show wave-like structures. George Thomson carried through the same research independently and in 1937 the two men shared the Nobel Prize for Physics.

DAVY, Humphry, 1778-1829. English chemist. As a laboratory assistant in Bristol in 1799, he discovered the respiratory effects of laughing gas. (nitrous oxide). He also discovered, by electrolysis, the elements sodium and potassium in 1807, and calcium, boron, magnesium, strontium and barium in 1808. In addition, he established that chlorine is an element and proposed that hydrogen is present in all acids. He invented the ‘safety lamp’ for use in mines where methane gas was present, enabling miners to work in previously unsafe conditions. In 1802 he became professor at the Royal Institute, London. He was elected president of the Royal Society in 1820.

DEMOCRITUS, 460-361 bc. Greek philosopher and speculative scientist who made a significant contribution to metaphysics with his atomic theory of the universe: that all things originate from a vortex of atoms and differ according to the shape and arrangement of their atoms. He was known as the ‘laughing philosopher’, and the ‘Aristotle of the 5th century’.

DIRAC, Paul Andrien Maurice, 1902-1984. British scientist who worked out a version of quantum mechanics consistent with special relativity. The existence of the positron (positive electron), was one of its predictions. He shared the Nobel Prize for Physics in 1933.

DOPPLER, Christian, 1803-1853. Austrian physicist. He became professor of experimental physics at the University of Vienna, and formulated ‘Doppler’s principle’. The ‘Doppler effect’ – a change in the observed frequency (or wavelength) of waves due to relative motion between the wave source and the observer. The effect is responsible for the perceived change in pitch of a siren as it approaches and then recedes, and for the ‘red shift’ of light from distant stars. ‘Red shift’ in astronomy is the lengthening of the wavelength of light from an object as a result of the object’s motion away from us. The ‘shift’ in light from galaxies is evidence that the universe is expanding.

DU FAY, C.F. de C. 1688-1739. French physicist who discovered positive and negative electricity. His greatest discovery was that electricity is of two kinds, one which may be produced by rubbing glass with silk, which he called ‘vitreous’, or glassy electricity; while the other, which he called ‘resinous’ electricity, may be produced by rubbing resin, amber and some other substances with flannel. He found that objects charged with the same kind of electricity repel each other, whilst objects charged with different kinds of electricity attract; i.e. Objects positively charged repel whilst positive and negatively charged objects will attract.

EDDINGTON, Arthur Stanley, 1882-1944. British astrophysicist who studied motions, equilibrium, luminosity and atomic structure of the stars. He became a leading exponent of Einstein’s theory of relativity. In 1919 his observation of the stars during an eclipse confirmed Einstein’s prediction that light is bent when passing near the Sun. In his book The Expanding Universe, 1933, he expressed the theory that in the spherical universe the outer galaxies or spiral nebulae are receding from one another.

In an address before the World Power Conference in Berlin, he described the energy stored away in matter, and said that the large amounts of coal and oil required to feed great power stations could one day disappear and a year’s supply of fuel will be carried in a teacup – thirty grammes of water, or anything else that is handy.

EDISON, Thomas Alva, 1847-1931. American scientist and inventor, born in Ohio of Dutch-Scottish parentage. He patented over 1,000 inventions. In Menio Park, New Jersey, between 1876 and 1887, he produced his most important inventions, including the electric light bulb, (1879). He invented the automatic repeater for telegraphic messages, the carbon transmitter, used as a microphone in the Bell telephone, and the phonograph and dictating machine. In 1882 he built an electrical power station in New York. It was the world’s first public electricity supply. He also designed the first British power station which was built in London.

EINSTEIN, Albert, 1879-1955. German born physicist who formulated the theory of relativity, and worked on radiation physics and thermodynamics. In 1905 he published his first theory – the so called restricted theory of Relativity, and in 1915 issued his general theory. His latest conception of the basic laws of the universe was outlined in his unified theory, made public in 1953.

Born at Ulm in Wurttenberg, West Germany, he lived with his parents in Munich and then in Italy. After teaching at the polytechnic school at Zurich, he became a Swiss citizen and was appointed an inspector of patents in Berne. In his spare time he took his PhD at Zurich. In 1909 he became a lecturer in theoretical physics at the university. After holding a similar post at Prague in 1911, he returned to teach at Zurich in 1912, and in 1913, took up a specially created post as director of the Kaiser Wilhelm Institute for Physics, Berlin. He received the Nobel Prize for Physics in 1921.

After being deprived of his position at Berlin by the Nazis, he emigrated to America in 1933 and became professor of mathematics and a permanent member of the Institute for Advanced Study at Princetown, New Jersey. During world war II he worked for the US Navy Ordnance Bureau.

EMPEDOCLES, 490-430 bc. Greek philosopher and scientist. He lived in Acragas, (Agrigfentum) in Sicily, and proposed that the universe is composed of four elements – fire, air, earth and water – which through the action of love and discord are eternally constructed, destroyed, and constructed anew. According to tradition, he committed suicide by throwing himself into the crater of Mount Etna.

EUCLID, 330-260 bc. Greek mathematician who lived and taught in Alexandria, Egypt, in the reign of Ptolemy I. He wrote ‘Stoicheia/Elements’ in 13 volumes of which nine deal with plane and solid geometry and four with number theory. His great achievement lay in the systematic arrangement of previous discoveries based on axioms, definitions and theorems. His works were unknown in Europe for over 1,000 years after his death and subsequently became standard school textbooks, and are still used in the 21st century.

EULER, Leonhard, 1707-1783. Swiss mathematician. He developed the theory of differential equations and the calculus of variations, also working in astronomy and optics. He was a pupil of Johann Bernoulli.

FAHRENHEIT, Gabriel, 1686-1736. German physicist and inventor of the Fahrenheit scale of temperature. Fahrenheit took as the zero point the lowest temperature he could achieve anywhere in the laboratory, and as another fixed point, body temperature which he set at 96F. On this scale, water freezes at 32F and boils at 212F. Intervals are measured in degrees F=Cx9/5 +32. The Fahrenheit scale was commonly used in English speaking countries until the 1970’s after which the Celsius scale was adopted in line with the rest of the world.

FARADAY, Michael, 1791-1867. English chemist and physicist, son of a blacksmith who became known as ‘the Shakespeare of research’ because of his great power of imagination. In 1812 he began researches into electricity and made his first electric cell. He became laboratory assistant to Humphry Davy at the Royal Institute in 1813, eventually succeeding him in 1833 as professor of chemistry. In 1821 he began experimenting with electromagnetism and ten years later discovered the induction of electric currents which produced three important inventions; the dynamo, the transformer and the electric motor. He subsequently found that a magnetic field will rotate the plane of polarisation of light. Faraday also investigated electrolosis. The ‘Farad’, a unit of electrical capacity is named after him.

FLEMING, John Ambrose, 1849-1945. English electrical physicist and engineer who invented the thermonic valve in 1904, used in radio receivers and transmitters until the advent of the transistor. He also devised a memory aid using the fingers to record the directions of a magnetic field, current and motion in an electric generator or motor. The three directions are represented by the thumb (for motion), the forefinger (for field), and second finger (for current) all held at right angles to each other. The right hand is used for generators and the left for motors.

FOUCAULT, John Bernard Leon, 1819-1868. French physicist, born in Paris; distinguished for his studies in optics and problems connected with light. He used the oscillation of a pendulum to demonstrate the rotation of the Earth around its axis. Another invention of his was the gyroscope.

FRANKLIN, Benjamin, 1706-1790. American scientist and politician. He proved that lightning is a form of electricity by the experiment of flying a kite in a storm, which led to the invention of the lightning conductor. He distinguished between positive and negative electricity. Franklin also discovered the course of the Gulf Stream a warm ocean current in the Atlantic.

A member of the Pennsylvania Assembly he was sent to Britain to lobby Parliament about tax grievances, and was prominent in the deliberations leading up to American independence. He helped draft the Declaration of Independence, and as Ambassador to France, he negotiated an alliance with France and the peace settlement with Britain.

FRAUNHOFER, Joseph Von, 1787-1826. German physicist who did important work in optics. Born in Bavaria, he was apprenticed to a glass cutter, and in 1807 he founded an optical institute. The dark lines in the solar spectrum (Fraunhoffer lines), which reveal the chemical composition of the Sun’s atmosphere were accurately mapped by him. By studying the lines produced by inserting known ‘absorbers’ in the path of light, scientists can make the spectroscope reveal far more than it otherwise would.

FRESNEL, Augustin, 1788-1827. French physicist who refined the theory of polarised light. Fresnel realised in 1821 that light waves do not vibrate like sound waves longitudinally in the direction of their motion, but traversely at right angles to the direction of the propagated wave.

GALILEO, properly Galileo Galilei, 1564-1642. Italian mathematician, astronomer and physicist. He developed the astronomical telescope and was first to see sunspots. He also observed the four main satellites of Jupiter, mountains and craters on the Moon, and the appearance of Venus going through ‘phases’, thus proving it was orbiting the Sun. In mechanics, Galileo discovered that free falling bodies, heavy or light, had the same constant acceleration, and that a body moving on a perfectly smooth horizontal surface would neither speed up or slow down.

He discovered in 1583 that each oscillation of a pendulum takes the same amount of time despite the difference in amplitude. He invented the hydrostatic balance, and discovered that the path of a projectile is a parabola. He was tried by the Church of Rome, under Pope Urban VIII, because he supported the Copernician Sun-centred view of the universe, against the Ptolemaic (Earth-centred) System. Although he was forced to re-cant his ideas, he is supposed to have remarked “But it moves for all that”. He lived his last years under virtual house arrest.

GALTON, Francis, 1822-1911. English scientist who studied the inheritance of physical and mental attributes in humans, with the aim of improving the human species. He discovered that no two sets of human fingerprints are the same, and is considered the founder of eugenics. From the Greek ‘well born’, the term was coined by Galton to study the ways in which the physical and mental quality of a people can be controlled and improved by selective breeding. The intention was to improve human intelligence and behaviour, but was abused by the German Nazi Party in the 1930’s.

GALVANI, Luigi, 1737-1798. Italian physiologist who discovered galvanic, or voltaic electricity in 1762 when investigating the contractions produced in the muscles of dead frogs by contact with pairs of different metals. His work led quickly to Alessandro Volta’s invention of the electric cell, and later to an understanding of how nerves control muscles. The galvanometer, an instrument for detecting small electric currents by their magnetic effects, was named after him.

GASSENDI, Pierre, 1592-1655. French physicist and philosopher, born in Provence, who contributed to the science of astronomy. He played a crucial role in the revival of atomism (the theory that the world is made of small indivisible particles), and the rejection of Aristotleism so characteristic of the period. He adopted the philosophy of Epicurus based on pleasure by rational satisfaction of a healthy mind and a healthy body.

GAUSS, Karl Frederick, 1777-1855. German mathematician who worked on the theory of numbers, non-Euclidean geometry, and the mathematical development of electric and magnetic theory. All measurements in magnetic phenomena are based on the system of absolute units proposed by Gauss. The unit of force is that force which gives unit velocity to unit mass in unit time – known as the ‘Dyne’. Gauss defined the unit of magnetic pole strength as that which exerts a force of one Dyne on an equal pole situated at a distance of one centimetre. A method of neutralising a magnetic field, used to protect ships from magnetic mines, is called ‘degaussing’.

GEIGER, Hans, 1882-1945. German physicist who produced in 1908, the Geiger counter, a device for detecting nuclear radiation and/or measuring its density by counting the number of alpha particles, positively charged particles, produced by radioactive decay. After studying in Germany, he spent the period 1907-1912 in Manchester working with Ernest Rutherford on radioactivity.

GIBBS, Josiah Willard, 1839-1903. American theoretical physicist and chemist who developed a mathematical approach to thermodynamics. His book ‘Vector Analysis’ (1881), established vector methods in physics. Gibbs’ function in thermodynamics, an expression representing part of the energy content of a system that is available to do external work, is known as free energy G.

GILBERT, William, 1544-1603. English scientist and physicist. He was the first profound student of magnetism and the leading man of science during the reign of Queen Elizabeth I. (and briefly under James I). He studied magnetism and static electricity, deducing that the Earth’s magnetic field behaves as if a bar magnet joined the North and South poles. His book on magnets, ‘De Magnete’, published in 1600, is the first printed scientific book based wholly on experimentation and observation. Gilbert showed that the attraction of amber, jet, glass, etc, was different from that of the magnet and called this new force, ‘electric’, the Greek name for amber, elektron.

GRAY, Stephen, 1696-1736. English physicist. He found in 1720 that electricity could be excited by the friction of hair, wool, silk or paper, and that some substances are conductors of electricity and others are not. His great experiment was a startling forerunner of the invention of the telegraph. He suspended a thread 886 feet long by loops of silk and sent over a current of electricity produced by rubbing glass.

GUERICKE, Otto Von, 1602-1686. German physicist, born at Magdeburg. He experimented on air, and invented the air pump. He earned his place in history by the invention of the first electric machine, a sulphur ball mounted on a shaft and rotated by a handle while rubbed by the operator’s hand, thus producing sparks. Guericke further discovered that electrified objects coming into contact with non-electrified substances readily communicate some of their electricity to the latter.

HEISENBERG, Werner Carl, 1901-1976. German physicist who developed quantum theory and formulated the uncertainty principle, which concerns matter, radiation, and their reactions, and placed absolute limits on the achievable accuracy of measurement. He was awarded the Nobel Prize in 1932 for his creation of quantum mechanics.

He was one of the few scientists to remain in Germany during the Nazi period, when he headed Hitler’s unsuccessful attempt to make an atom bomb.

HELMHOLTZ, Herman Ludwig Ferdinand von, 1821-1894. German physiologist and physicist, and inventor of the ophthalmoscope for examining the inside of the eye. He was the first to explain how the cochlea of the inner ear works, and the first to measure the speed of nerve impulses. He also worked on thermodynamics.

In physics he formulated the law of conservation of energy, which says that no energy is created or destroyed. Yet it was found that radium constantly threw off great quantities of energy in the shape of heat, light and electricity, without seeming to lose any of its weight and power. Old ideas had to be readjusted, but careful experiments soon showed that radium does lose some of its weight, but the slowness of decay compared with the vast energy produced upset all previous concepts of physical energy.

HENRY, Joseph, 1797-1878. American physicist, followed the work of English scientist William Sturgeon improving the electro-magnet, and in principle, invented the electric telegraph, althought it was left to Samuel Morse to work it out. He published an account of his discovery of the principle of electro-magnetic induction, and the phenomenon of self-induction in 1832, before the news of Michael Faraday’s success in the same field had reached him. A unit of inductance, the henry, is named after him.

HERSCHEL, William, 1738-1822. German born English astronomer. He was a skilled telescope maker, and pioneered the study of binary stars and nebulae. He discovered the planet Uranus in 1781, and infra-red solar rays in 1801.

Born in Hanover he came to England in 1757 and became a professional musician and composer while instructing himself in mathematics, astronomy, and constructing his own reflecting telescope. While searching for double stars, he found Uranus, and later, several of its satellites. This brought him instant fame, and in 1782, the post of private astronomer to George III. He discovered the motion of double stars around one another. In 1789 he built at Slough the largest telescope in the world at that time, and catalogued over eight hundred double stars and found over two thousand nebulae. By studying the distribution of stars, Herschel established the basic form of our Galaxy, the Milky Way.

HERTZ, Heinrich, 1857-1894. German born physicist who studied electro-magnetic waves, showing that their behaviour resembles that of light and heat waves. Maxwell’s theory that light and electricity were essentially the same did not gain immediate acceptance. However, seven years after Maxwell’s death, Hertz performed his crucial experiment at his laboratory in Karlsruhr, in which he produced the electro-magnetic waves which the theory required. This demonstration finally disposed of the opposition. Hertz was able to measure the length and speed of electro-magnetic waves whose frequency are now named after him and often measured in megahertz, symbol Mhz. He died at the early age of 37.

HOOKE, Robert, 1635-1703. English scientist and inventor, born at Freshwater on the Isle of Wight. He was considered the foremost mechanic of his time, and originator of Hooke’s law, 1676, which states that the tension on a lightly stretched spring is proportional to its extension from its natural length. His inventions included the spirit level, balance spring of watches, marine barometer, and sea gauge. In biology he coined the term ‘cell’.

Hooke studied elasticity, furthered the science of mechanics and microscopy, and made important improvements to such scientific instruments as the microscope, telescope, barometer and quadrant.. Quick to deduce natural laws, he anticipated Newton’s theory of gravitation, and foresaw the application of steam to machinery. He was elected to the Royal Society, and became professor of Geometry at Gresham College, London. (1665). He designed several buildings including the College of Physicians in London.

HUYGENS, Christian, 1629-1695. Dutch mathematician, physicist and astronomer who published his wave theory of light in 1690. He maintained that there must be a substance which is far thinner than the lightest gas, a substance that has no conceivable weight, and so fine that it penetrates between the smallest molecules and atoms, and that spreads through all space to the farthest star and beyond that. This was the ether. He also developed the pendulum clock, discovered polarisation, and observed Saturn’s rings.

JEANS, James Hopwood, 1877-1946. British mathematician and astronomer. Born in London, he lectured on applied mathematics at Cambridge and Princetown. In physics he worked on the kinetic theory of gases, and on forms of energy radiation. In astronomy, his work focused on giant and dwarf stars, the nature of spiral nebulae, and the origin of the cosmos. He did much to popularise astronomy. He was knighted in 1928, and received the Order of Merit in 1939.

JOULE, James Prescott, 1818-1889. English physicist, born in Manchester, whose work on the relations between electrical, mechanical and chemical effects led to the first law of Thermodynamics. (see Helmholtz). He gave his name to the Joule, a unit of work and energy, defined as the work done in one second by a current of one ampere at a potential difference of one volt. One watt is equal to one Joule per second.

The Joule-Kelvin effect in physics concerns the fall in temperature of a gas as it expands adabatically through a narrow jet – the basic principle of most refrigerators.

KELVIN, (William Thomson) Lord, Baron Kelvin, 1824-1907. Irish physicist who introduced the Kelvin scale – the absolute scale of temperature used by scientists. It begins at absolute zero (-273.16C) and increases by the same degree intervals as the Celsius scale; that is, 0C is the same as 273K, and 100C is 373K. Kelvin’s work on the conservation of energy in 1851 led to the second law of thermodynamics – that it is impossible for an unaided self-acting machine to convey heat from one body to another at a higher temperature.

He also contributed to telegraphy by developing stranded cables and sensitive receivers, greatly improving transatlantic communications. Maritime endeavours led to a tide gauge and predictor, an improved compass, and simpler methods of fixing a ship’s position at sea.

KEPLER, Johan, 1571-1630. German mathematician and astronomer. Born in Wurttenberg, he became assistant to Tycho Brahe at Prague (1600) and succeeded him as Imperial mathematician in 1601. His analysis of Brahe’s observation of the planets led him to discover his three laws, the first two of which he published in ‘Astronomia Nova’ (1609), and the third in ‘Harmonices Mundi’ in 1619.

Now called Kepler’s Laws of planetary action there are:-

(1) the orbit of each planet is an ellipse with the Sun at one of the foci;
(2) the radius vector of each planet sweeps out equal areas in equal times; and,
(3) the squares of the periods of the planets are proportional to the cubes of their mean distances from the Sun.

KIRCHER, Athanasius, 1601-1680. German mathematician. In 1646 he constructed the first projection lantern, the ‘Lanterna Magica’.

KIRCHOFF, Gustav Robert, 1824-1887. German physicist. He was known for his laws of electrical circuit theory; (1) the total current entering any junction in a circuit is the same as the total current leaving it; (2) the sum of the potential drops across each resistance in any closed loop in a circuit is equal to the total electromotive force acting in the loop.

With Bunsen, he developed spectroscopy and explained ‘Fraunhoffer Lines’ in the solar spectrum. He used spectroscopy to discover several elements in the Sun. He devised means of investigating ‘black body’ radiation – a hypothetical object that completely absorbs all thermal radiation, and is a perfect emitter of the same.

LAWRENCE, Ernest Orlando, 1901-1958. American physicist. His invention of the cyclotron particle accelerator pioneered the production of artificial radio isotopes. He was professor of physics at the University of California, Berkeley, from 1930, and director from 1936 of the Radiation Laboratory which he built into a major research centre for nuclear physics. He was awarded the Nobel Prize in 1939.

LEIBNITZ, Gottfried Wilhelm, 1646-1716. German mathematician and philosopher. Born at Leipzig, his versatile genius soon showed itself, and at the age of twenty he was offered a professorship at the University of Altdorf. Independently of, but concurrently with the British scientist Issac Newton, he developed the branch of mathematics known as differential and integral calculus. In his metaphysical works he argued that everything consisted of innumerable units, (Monads), the individual properties of which determined each thing’s past, present and future. Monads, although independent of each other, interacted predictably: This meant that Christian faith and scientific reason need not be in conflict, and that ‘this is the best of all possible worlds’. His works Theodicy and Monadology were published in 1710 and 1714 respectively.

LEONARDO da VINCI, 1452-1519. Italian painter, sculptor, architect, engineer and scientist, one of the greatest figures of the Italian Renaissance. As state engineer and court painter to the Duke of Milan, he painted many masterpieces, including the Mona Lisa, which are now world renowned. Leonardo’s greatest legacies were the notebooks and drawing which show an immensely inventive and enquiring mind, studying aspects of the natural world from anatomy to aerodynamics. He invented ‘aerial perspective’ whereby the misty atmosphere blurs and changes the colours of the landscape as it dissolves into the distance. The most famous collection of his notes, which includes drawings of a tank, a helicopter, and a submarine, is the ‘Atlantic Codex’ in Windsor Castle.

LORENTZ, Hendrik Anton, 1853-1928. Dutch physicist, winner, with his pupil Pieter Zeeman, of a Nobel Prize in 1902 for work on the Zeeman effect. This discovery was made in 1896 – that when light from certain elements, such as sodium or lithium, (when heated), is passed through a spectroscope in the presence of a strong magnetic field, the spectrum splits into a number of distinct lines.

MARCONI, Guglielmo, 1874-1937. Italian electrical engineer and pioneer, and the first to devise a practical system for telegraph by means of radio waves. In 1895 he achieved radio communication over more than a mile, and in England in 1896, he conducted successful experiments that led to the formation of the Marconi Wireless Telegraph Company. In 1898 he successfully transmitted signals across the English channel, and used radio to report on the Americas Cup Yacht Race.(1899). In 1901 established communication between Poldhu in Cornwall and St. John’s, Newfoundland. During the first World War he developed short-wave radio, initially used for warfare. His discoveries were later applied to the transmission of signals over large distances at greatly increased power. In 1918 he sent the first radio message from Britain to Australia. He shared the Nobel Prize for Physics in 1909 with Carl Ferdinand Braun.

MAXWELL, James Clerk, 1831-1879. Scottish physicist. Born in Edinburgh, he was professor of natural philosophy at Aberdeen (1856-1860), and then physics and astronomy in London. In 1871 he became professor of experimental physics at Cambridge and wrote many principle works on science.

His major achievement was in the understanding of electromagnetic waves: Maxwell’s equations brought together electricity, magnetism and light in one set of relations and were regarded as the closing of the fluid theory era, and the idea of electricity as something more elusive and less obvious. He contributed to every branch of physical science, studying gases, optics, and the sensation of colour. His theoretical work on magnetism prepared the way for wireless telegraphy and telephony.

MAYER, Julius Robert von, 1814-1878. German physicist who in 1842 anticipated James Joule in devising the mechanical equivalent of heat, and Herman Helmholtz in the principle of the conservation of energy.

In 1842 he published a paper on ‘The Forces of the Inanimate Nature’ which was regarded by many as marking the beginning of Thermodynamics.

MERESENE, Marin, 1588-1648. French theorist, philosopher and naturist. In 1636 he published his most important work, ‘Harmonie Universelle’, which gave a full description of all the contemporary musical instruments of his time.

NEWTON, (Sir) Issac, 1642-1727. English physicist and mathematician who laid the foundations of physics as a modern discipline. Born at Woolsthorpe, Lincolnshire, he was educated at Grantham grammar School and Trinity College, Cambridge, of which he became a fellow in 1667.

He created calculus, discovered that white light is composed of many colours, and developed the three standard laws of motion still applicable today. During 1665-66, he discovered the bimonial theorem, differential and integral calculus, and began to investigate the phenomenon of gravitation. In 1685, his The Mathematical Principles of Natural Philosophy was a major work and expounded his universal law of gravitation.

Newton constructed a simple reflecting telescope in 1668. (The Newtonian telescope). It used a parabolic mirror to direct light to a focus at the side of the tube by a flat secondary mirror placed at 45 degrees to the optical axis. He was elected Fellow of the Royal Society for his discovery.

Newton resisted James the Second’s attacks on the liberties of the universities, and sat in the parliaments of 1689 and 1701 as a Whig. He was appointed warden of the Royal Mint in 1696, and master in 1699, when he carried through a reform of the coinage. He was elected president of the Royal Society in 1703 and was knighted by Queen Anne in 1705, becoming the first person to be honoured this way for scientific achievement. Most of the last thirty years of his life were taken up by studies of theology and chronology, and experiments in alchemy. He was buried in Westminster Abbey.

OERSTED, Hans Christian, 1777-1851. Danish physicist who founded the science of electromagnetism. In 1820 he discovered the magnetic field associated with an electric current. The ‘Oersted’ (symbol Oe) a unit of magnetic field strength, is now replaced by the ampere per metre. The Earth’s magnetic field is about 0.5 Oersted; the field near the poles of a small bar magnet is several hundred Oersteds; and a powerful electromagnet can have a field strength of thirty-thousand Oersteds.

OHM, Georg Simon, 1787-1854. German physicist who studied electricity and discovered the fundamental law of resistance in 1827, i.e. the property of a conductor that restricts the flow of electrons through it. The unit was originally defined with reference to the resistance of a column of Mercury when a potential difference of one volt between them produced a current of one ampere. The SI unit of electrical resistance is named after him, and the unit of conductance, the Mho. Not all conductors obey Ohm’s Law; those that do are called ohmic conductors.

PASCAL, Blaise, 1623-1662. French philosopher and mathematician. In 1641 he invented the first arithmetical calculating machine that would count tens. He contributed to the development of hydraulics, the calculus, and the mathematical theory of probability. ‘Pascal’s triangle’, an array of numbers with 1 at the apex in which each number is the sum of the pair of numbers above it, was used in his study of probability.

In hydraulics he discovered the principle of the hydraulic ram; liquids not being compressible, pressure exerted on any part in a closed vessel will be transmitted equally to all parts of the liquid. The pascal unit of pressure (symbol Pa) is equal to one ‘newton’ per square metre. It replaced bars and millibars. (10 to the power of 5 Pa = one bar).

PLANCK, Max Karl Ernst Ludwig, 1858-1947. German physicist who framed the quantum theory in 1900. His research into the manner in which heated bodies radiate energy led him to report that energy is emitted only in indivisible amounts, called quanta, the magnitude of which are proportional to the frequency of the radiation. His discovery ran counter to classical physics and is held to have marked the commencement of modern science. He was awarded the Nobel Prize for Physics in 1918.

POISSON, Simeon Denis, 1781-1840. French applied mathematician. In probability theory he formulated the ‘Poisson distribution’, which is widely used in probability calculations.

PTOLEMY, (Claudius Ptolemaeus), 100-170. Egyptian astronomer and geographer who worked in Alexandria. His ‘Almagest’ developed the theory that the Earth is the centre of the universe, with the Sun, Moon and stars revolving around it. Ptolemy’s ‘Geography’ was a standard source of information and was accepted by the Christian Church and not challenged until 1543 when the Polish astronomer Copernicus proposed an alternative to the Ptolemaic system. Ptolemy also wrote treatises on optics, geometry and music, as well as a famous (if inaccurate) ‘Guide to Geography’.

PYTHAGORAS, 580-500 bc. Greek mathematician and philosopher who formulated the ‘Pythagorus theorem’. Much of his work concerned numbers, to which he assigned mystical properties. For example, he classified numbers into triangular ones, (1,3,6,10,…), which can be represented as a triangle array, and square ones, (1,4,9,16,…), which form squares. He also observed that any two adjacent triangular numbers add to a square number. For example, 1+3=4, 3+6=9; 6+10=16, etc.

Pythagorus’ theorem in geometry states that in a right- angled triangle, the area of the square on the hypotenuse (the longest side) is equal to the sum of the areas of the squares drawn on the other two sides. The theorem provides a way of calculating the length of any side of a right-angle triangle if the length of the other two sides are known. It is also used to determine certain other trigonometric relationships.
(Pythagorus’ theorem is likely to have been known long before his time. It was probably used by the Egyptians to lay out the pyramids.)

RAYLEIGH, John W. Strutt, 3rd Baron, 1842-1919. British physicist. Born is Essex, he was professor of experimental physics at Cambridge (1879) and of natural philosophy at the Royal Institute, 1887-1905. He wrote the standard ‘Treatise on Sound’; experimented in optics and microscopy, and, with William Ramsay, discovered argon. He was awarded the Nobel Prize in 1904.

ROEMER, Olous, 1644-1710. Danish astronomer. In 1676 he discovered the finite velocity of light, and that light takes time to go across space. In 1706 he produced his catalogue of astronomical observations.

RONTGEN, Wilhelm Konrad, 1845-1928. German physicist. Born at Lennep, he became director of the Physical Institute at Glessen in 1879, and at Wurtzburg in 1885, where he conducted his experiments which resulted in the discovery of Rontgen Rays, (X-Rays, 1895).

While investigating the passage of electricity through gases, he noticed the fluorescence on the barium platinocyanide screen. This radiation passed through some substances opaque to light, and affected photographic plates. Developments from this discovery have revolutionised medical diagnosis.

He was awarded the Nobel Prize in 1901.

ROWLAND, Henry Augustus, 1848-1901. American physicist. He worked on the diffraction grating invented by Fraunhoffer. Light reflected against a mirror etched with fine parallel lines, break up the light which is reflected as a spectrum. In 1882, by using a concave mirror, Rowland increased the usefulness of this kind of spectroscopy.

RUMFORD, Benjamine Thompson, (Count Rumford), 1753-1814. American born British physicist. In 1798, impressed by the seemingly inexhaustible amounts of heat generated in the boring of a cannon, he published his theory that heat is a mode of vibratory motion, not a substance.

Rumford spied for the British during the American revolution, and was forced to flee to England in 1776. He travelled in Europe, and was created a Count of the Holy Roman Empire for services to the elector of Bavaria in 1791. He founded the Royal Institute in London in 1799.

RUTHERFORD, Ernest, 1871-1937. British physicist, a pioneer of modern atomic science. His main research was in the field of radioactivity. He discovered alpha, beta and gamma rays. He named the nucleus, and was the first to recognise the ionising nature of the atom.

Born at Nelson in New Zealand son of a farmer, and one of twelve children. At the age of twenty-eight he became professor of experimental physics at the modern McGill University, Montreal, (1898); Manchester (1907) and Cambridge, (1919), where he was also director of the Cavendish Laboratory. He was awarded the Nobel Prize for Chemistry in 1908, and knighted in 1914. He became a Fellow of Trinity College, Cambridge, in 1919. In 1925. he received the Order of Merit, and became president of the Royal Society. In 1931 he was created Baron Rutherford of Nelson, New Zealand, in honour of his services to science.

SCHRODINGER, Erwin, 1887-1961. Austrian physicist who greatly advanced the study of wave mechanics. Born in Vienna, he became senior professor at the Dublin Institute for Advanced Studies in 1940. He shared (with Paul Dirac) the Nobel Prize for Physics in 1933.

SNELL, Willebrord, 1581-1628. Dutch mathematician and physicist who devised the basic law of refraction in 1621, known as Snell’s Law. This states that the ratio between the sine of an angle of incident and the sine of an angle of refraction is constant. The laws describing the reflection of light were well known in antiquity, but the principles governing the refraction of light were little understood. Snell’s Law was published by the French mathematician Descartes in 1637.

SODDY, Frederick, 1877-1956. English physicist, chemist and monetary reformer. Born at Eastbourne, he worked with Rutherford, and was professor of Chemistry at the University of Aberdeen (1914), and Oxford (1919). He pioneered research into atomic disintegration and the displacement law of radioactivity. In 1912 he published the discovery of, and coined the term, ‘Isotope’. He also published a number of works on radioactivity and atomic energy. He was awarded the Nobel Prize in 1921 for investigating the origin and nature of isotopes.

STOKES, George Gabriel, 1819-1903. Irish physicist and mathematician. During the late 1840’s he studied the viscosity (resistance of relative motion) of fluids. This culminated in Stokes Law, which applies to a force acting on a sphere falling through a liquid. He was professor of mathematics at Cambridge University from 1849, and was renowned for his researches into the theory of light.

THALES, 640-546 bc. Greek philosopher and scientist. He lived in Miletus, Asia Minor. Thales made advances in geometry, and predicted an eclipse of the Sun in 585 bc. As a philosophical materialist, he theorised that water was the first principle of all things; that the Earth floated on water, and so proposed an explanation for earthquakes.

THOMSON, Joseph John, 1854-1940. English physicist. Thomson won a scholarship to Cambridge in 1876 and was associated with the university for the rest of his life. He became professor and founder of the Cavendish Laboratory of experimental physics (1884-1918), and later, master of Trinity College. His discovery of the electron (1897) revolutionised the theory of atomic structure. In 1906 he received the Nobel Prize for Physics for his researches into the conduction of electricity through gases exposed to X-Rays. Thomson was also an outstanding teacher; seven of the men who worked under him were later awarded the Nobel Prize.

TORRICELLI, Evangelista, 1608-1647. Italian physicist and pupil of Galileo. He invented the mercury barometer, the form of weather barometer now in common use. The principle of the Torricellian vacuum in a mercury tube is accredited to him. With Boyle and Mariotte, he was among the first to establish the properties of the atmosphere and gases.

VOLTA, Alessandro, 1745-1827. Italian physicist who invented the first electric cell, (the ‘Voltaic Pile’); the electrophorus (an early electrostatic generator); and an electroscope, (a device for measuring static electricity). He was professor of Physics at the University of Parvia,

Volta was known for his researches into electricity. He proved that zinc and copper plate in contact have a slight difference of electric charge, and showed that if several pairs of plates, separated by cloths moistened with a salt solution were connected together, a steady electric current was produced. Hence the Voltaic Pile or Battery. The device was sometimes referred to as the ‘galvanic battery’ in honour of Galvani’s ‘dead frog’ experiments.

The Volt, a unit of electrical force (symbol V) is named after him. The absolute Volt is defined as the potential difference necessary to pass a current of one ampere through an electrical circuit with a resistance on one ohm.

Volta demonstrated his ‘cell’ to Napoleon who made him a count and senator of the kingdom of Lombardy

WILSON, Charles Thomson Rees, 1869-1959. British physicist who in 1911 invented the Wilson cloud Chamber. As a young assistant in the Cavendish Laboratory in Cambridge, he was asked by J.J.Thomson if an apparatus could be devised for photographing electrons. Wilson filled a glass tube with dust free air and water vapour. When electrons were sent through the tube each condensed some water around itself, and its way across the tube was marked by a thin streak of mist which could be photographed. Hence the cloud chamber for the first time produced an optical record of atomic particles. He shared the Nobel Prize for Physics with Arthur Holly Compton in 1927.

YOUNG, Thomas, 1773-1829. British physicist who revived the wave theory of light and identified the phenomenon of interference in 1901. A child prodigy, he mastered most European languages and many eastern tongues by the age of twenty. He had also absorbed the physics of Newton and the chemistry of Lavoisier. He further displayed his versatility by publishing an account of the Rosetta Stone. The work played a crucial role in the decipherment of hieroglyphics by Jean Francois Champollion, (1790-1832), the French Egyptologist.