French physicist who applied mathematical formulæ to the relation between electric currents and magnetism. His first paper was presented one week after he heard of the Danish physicist Hans Christian Ørsted's observations that electric currents produce magnetic fields. He later invented the solenoid and he showed that parallel wires with current in the same direction attract and wires with current in opposite directions repel each other. In 1814 he independently determined Avogadro's law and later also developed a wave theory of heat. He was greatly affected by his father's execution during the French Revolution and by his first wife's untimely death. He personally formulated the words on his tombstone: "Tandem felix" (happy at last).
Ångström, Anders Jonas (1814-1874)
Swedish physicist who was one of the founders of spectroscopy. He proposed in 1853 the relationship between emission and absorption spectra of chemical elements, which was more clearly articulated by Gustav Kirchhoff in 1859. In 1861, Ångström discovered hydrogen lines in the solar spectrum and subsequently confirmed the likely existence of other elements in the sun. In 1867 he initiated spectral studies of auroras and, a year later, published an authoritative map of the sun's spectral lines with wavelengths expressed in the unit today known as the ångström unit.
Archimedes of Syracuse (ca 287-212 BC)
Archimedes was the greatest scientist and mathematician of ancient times. He calculated the area of a sphere and an ellipse and discovered that the volume of a sphere is two thirds of the volume of the smallest cylinder that can contain it. He showed that p has a value between 3 10/71 and 3 1/7. Archimedes was also an outstanding engineer who formulated the principle of buoyancy (today called Archimedes' principle), invented the catapult, the Archimedes' screw, a device still used, and constructed lenses which could focus the sun's light. It is said that he was killed by a Roman soldier when he had snapped at him "Don't perturb my circles", referring to a geometric figure he had outlined in the sand.
Becquerel, A. Henri (1852-1908)
French physicist who in 1896 accidentally discovered radioactivity while investigating fluorescence in uranium salts. For this he shared the 1903 Nobel Prize in physics with Marie and Pierre Curie. He discovered that the radiation from uranium and radium comprised electrons. The only place these electrons could be coming from was from within the atoms. At a stroke this observation destroyed the nineteenth century conception of atomic structure.
Bohr, Niels (1885-1962)
Danish physicist who was the first to apply quantum theory to atomic structure and thus founding the modern quantum theory of matter. His atom model from 1913 assumed that electrons orbit the nucleus at precise distances from the nucleus without loosing energy, and that the angular momentum associated with an allowed motion is an integral multiple of h/2p. He proposed that radiation is emitted when an electron jumps from one orbit (one quantum number) to another. In 1922 Bohr was awarded the Nobel Prize for physics. In 1943 Bohr and his family moved to the United States, where he participated in the atomic bomb project at Los Alamos. After the war he returned to Denmark.
Boltzmann, Ludwig (1844-1906)
Austrian physicist who (with J. W. Gibbs) developed the branch of physics called statistical mechanics. In the 1870s he obtained the Maxwell-Boltzmann distribution and explained the second law of thermodynamics by applying laws of probability to atomic motion. His work was opposed by many European physicists, and depressed and in poor physical health he committed suicide in 1906. Shortly thereafter the French scientist Jean Perrin verified much of his work.
de Broglie, Louis (1892-1987)
French physicist who in 1923 proposed the wave nature of material particles, which was experimentally confirmed for the electron in 1927. The wave concept of the electron was included in Schrödinger's wave mechanical picture of the atom. De Broglie has also written numerous popular works, including New Perspectives in Physics (1962). In 1929 he received the Nobel Prize for physics.
Celsius, Anders (1701-1744)
Swedish astronomer who in 1742 pubished the first precise determination of two fixed points on a temperature scale and thus formed a true international scale. He suggested zeroÊdegrees to be the boiling point of water and 100Êdegrees to be the freezing point. The opposite appeared some years later with no specific originator. Celsius also studied the Earth's magnetic field and published descriptions of the northern light. As professor of astronomy at Uppsala University he built an observatory, but only three years after it was built he died in tuberculosis.
Compton, Arthur Holly (1892-1962)
American physicist who described the behaviour of X-rays when they interact with electrons. In 1923 he found that when X-rays strike graphite they are scattered and their wavelengths are increased. This discovery, known as the "Compton effect", was the first proof that X-rays can behave like particles. For this discovery he shared the 1927 Nobel Prize in physics with C.T.R. Wilson, a Scottish physicist who received his share for inventing the cloud chamber, which is used to view tracks of charged nuclear particles. Compton suggested the name "photon" for the light quantum.
Copernicus, Nicholaus (1473-1543)
Polish astronomer and mathematician who is often considered the founder of modern astronomy. Polish name: Mikolaj Kopernik. By postulating (1) the rotation of the Earth, (2) revolution of the planets around the sun, and (3) the tilt of the Earth's rotational axis, Copernicus worked out a heliocentric model of the solar system in full mathematical detail. The sun was in this model slightly offset from the centre of the solar system. Out of fear that his ideas would get him into trouble with the church, his paper De Revolutionibus Orbium Coelestium, which was outlined in 1514, was delayed and published just before his death in 1543.
Curie, Marie, born Sklodowska (1867-1934)
Polish-French physicist and chemist who gave the name "radioactivity" to the emission of radiation from atoms. Together with her husband Pierre Curie she studied radioactivity which in 1898 led to the discovery of the elements radium and polonium. In 1903 they shared the Nobel Prize in physics with Henri Becquerel. In 1911 Marie Curie received a second Nobel Prize, this time in chemistry for the isolation of pure radium. The Curies refined eight tons of raw ore to produce one gram of radium. In 1935 Marie and Pierre's daughter, Iréne Joliot-Curie, and son-in-law Frédéric Joliot-Curie received the Nobel Prize for chemistry. Marie Curie died of leukemia caused by overexposure to radioactivity.
Curie, Pierre (1859-1906)
French physicist and chemist, married to Marie Curie. He discovered the phenomenon of piezoelectricity and constructed a torsion balance with a tolerance of 0.01 mg. He also discovered that the magnetic susceptibility of paramagnetic materials is inversely proportional to the absolute temperature (Weiss-Curie law) and that there exists a critical temperature above which the magnetic properties disappear (the Curie temperature). Pierre Curie joined his wife's work with researching the nature of radioactivity, and for this he shared the 1903 Nobel Prize for physics with Henri Becquerel and his wife. In 1906 he died in a traffic accident in Paris, at the age of 46.
Dirac, Paul A. M. (1902-1984)
English mathematician and theoretical physicist who predicted the existence of antimatter. The positron (anti-electron) was subsequently discovered in 1932 by Carl Anderson. Dirac also developed a relativistic version of the Schrödinger equation, known as the Dirac equations, and provided the first rigorous description of the spin of elementary particles. In 1933 he shared the Nobel Prize for physics with Erwin Schrödinger.
Einstein, Albert (1879-1955)
Einstein is the most well-known scientist of the 20th century. In 1905 he published three papers in Annalen der Physik, the leading German physics journal. In the first paper he proposed that light could behave as packets of energy and that the energy of these light quanta, as he called them, were proportional to the frequency. He went far beyond Planck's work and used this interpretation to explain the photoelectric effect. The second paper concerned statistical mechanics and explained the Brownian motion. In the third paper "On the Electrodynamics of Moving Bodies" he proposed the theory of special relativity, which was based on two postulates: (1) the physical laws are the same in all inertial reference systems, and (2) the speed of light is the same in every inertial reference system. Later in 1905 Einstein derived the equivalence between mass and energy (E = mc2). Late 1915 Einstein published his General Theory of Relativity, which postulated that uniform acceleration and a gravitational field were equivalent. It predicted that the light from distant stars would bend slightly when passing near the sun, which was confirmed during an eclipse of the sun in 1919. Einstein was born in Germany, at the age of 22 he became a Swiss citizen, and in 1933 he moved to the United States and became a US citizen in 1940. When he in 1921 received the Nobel Prize for physics he was awarded for his explanation of the photoelectric effect, which shows that the world was still sceptical to his ideas on relativity.
English chemist and physicist who is known for his pioneering experiments in electricity and magnetism and who is one of the greatest experimentalists of all time. He found the principle of induction and invented the dynamo, which produces electricity by mechanical means. His research of electrolysis led to the laws known today as Faraday's laws of electrolysis. Faraday discovered that an intense magnetic field can rotate the plane of polarized light, which today is known as the Faraday effect. He also introduced the concept of fields to describe magnetic and electric forces and advocated the law of energy conservation.
Fermi, Enrico (1901-1954)
Italian physicist who in 1938 escaped the fascism in Italy and emigrated to the United States, where he became a citizen in 1944. In 1938 he was awarded the Nobel Prize for physics for the discovery of artificially radioactive elements, produced by neutron irradiation, and for the discovery of nuclear reactions induced by slow neutrons. He divided elementary particles into two groups, today known as fermions and bosons, depending of their spin characteristics. Fermi is well-known for leading a group of scientists who on Dec 2nd 1942 achieved the first man-made and self-sustaining nuclear chain reaction, which led to the construction of the atomic bomb and nuclear power plants.
Fresnel, Augustin (1788-1827)
French physicist who made fundamental contributions to theoretical and applied optics. Fresnel rejected the view derived from Newton that light consists of particles (corpuscles) and established a wave theory on a firm mathematical and experimental basis. He developed the Fresnel equations of reflection and refraction and developed a mathematical theory of refraction and polarization. In 1819 Poission found that as a consequence of Fresnel's theory, the centre of the shadow of a diffracting disk should be illuminated. This unexpected effect was subsequently observed, verifying Fresnel's theory.
Galilei, Galileo (1564-1642)
Italian scientist who showed that all bodies fall at the same rate. This opposed Aristotelian physics, which assumed that speed of fall is proportional to weight. Galilei described dynamics and statics and emphasized the use of mathematics. He said that motion is continuous and can only be altered by the application of a force. In 1604 he observed a supernova and when he failed to determine its parallax, he concluded that the star must be very distant. In 1609 Galilei built a 20-power telescope and found sunspots, craters on the moon, the four largest satellites of Jupiter, and the phases of Venus. He found the Copernican theory to be correct, but the church forced him to recant his conviction. In 1633 the church condemned him to life imprisonment for "vehement suspicion of heresy".
Gamow, George (1904-1968)
Russian-born American physicist who contributed significantly to our knowledge of nuclear reactions within stars, in particular he found that stars tend to become hotter when their hydrogen is depleted. Gamow also worked out a theory of alpha decay in terms of tunnelling through the nuclear potential barrier. He strongly supported the Big Bang theory of Georges Lemaitre. Gamow is well-known as an author of, for example, "Mr Tompkins Explores the Atom", "Atomic Energy in Cosmic and Human Life", "The Creation of the Universe", "Matter, Earth, and Sky", "A Planet Called Earth", "Thirty Years that Shook Physics", and "A Star Called the Sun".
German theoretical physicist who is best know for his uncertainty principle. In 1925 Heisenberg invented matrix mechanics, the first version of quantum mechanics. For this work and for the extension of it into a complete mathematical theory of the behaviour of atoms and their components, he was in 1932 awarded the Nobel Prize for physics. During World War II he headed the unsuccessful German nuclear weapon project.
Hubble, Edwin (1889-1953)
American astronomer, the founder of extragalactic astronomy, who in 1925 composed the classification scheme for the structure of galaxies which is still in use. He demonstrated that the Andromeda nebula was far outside the Milky Way and found observational evidence for an expanding universe. Hubble used cepheid variables to determine the distance to other galaxies and proposed, in 1929, the Hubble law for distances to other galaxies, but his original value of the Hubble constant (526 km s-1 Mpc-1) was not very accurate.
Huygens, Christian (1629-1695)
Dutch astronomer, mathematician and physicist who proposed a wave theory of light. In 1656 he invented the pendulum clock, which greatly increased the accuracy of time measurements. In the early 1650s he and his elder brother discovered a new method of grinding and polishing lenses, and with one of his lenses he 1655 discovered a Saturn satellite and the rings of Saturn. Huygens also published work on probability theory, stated that the centre of gravity moves uniformly in a straight line, and found the mathematical expression for the centrifugal force. But he disagreed with Newton's theory of gravity.
Joule, James P. (1818-1889)
English physicist who found that the power lost in a resistor is given by P = R I2, a law known as Joule's law. He found that the heat produced by different kinds of energy was proportional to the energy expended, and thus established the equivalence between heat and mechanical energy. In 1853 Joule and William Thomson (Lord Kelvin) observed that when an ideal gas expands at a low temperature without performing work (isenthalpic expansion), its temperature falls. This phenomenon, which today is known as the Joule-Thomson effect, is applied in cryogenetic work, ie work done in the temperature range 0 - 100 K.
Kelvin, William Thomson (1824-1907)
William Thomson, who became Lord Kelvin of Largs (Scotland) in 1892, was one of Great Britain's foremost scientists and inventors. He published more than 650 scientific papers and patented some 70 inventions. Thomson was born in Belfast, Ireland, and in 1832 the family moved to Glasgow, Scotland. Young Thomson entered the university when he was ten. He is best known for developing the Kelvin temperature scale and for observing the Joule-Thomson effect. His participation in the transatlantic submarine cable project in 1866 formed the basis of a large personal fortune.
Kepler, Johannes (1571-1630)
German astronomer and mathematician who used the astronomical observations of Tycho Brahe to formulate the three laws of planetary motion that are named after him. Kepler studied optics and developed the concept of rays. He also improved the early telescopes, invented a convex eyepiece and discovered a means of determining the magnifying power of lenses. In his work Kepler was side-tracked by his interest in mystic notions. For example, he believed in "the music of spheres" and like many astronomers in those days he threw himself into casting horoscopes.
Kirchhoff, Gustav (1824-1887)
German physicist who, in collaboration with Robert William Bunsen, developed the science of spectrum analysis. Kirchhoff showed that each element, when heated to incandescence, produced a characteristic pattern of emission lines. This led to the discovery of cesium (in 1860) and rubidium (in 1861). His investigations of the emissive power of the radiation of a black body led Planck to a quantum hypothesis in 1900. He also formulated Kirchhoff's laws for electric circuits.
Maxwell, James Clerk (1831-1879)
Scottish physicist who made numerous contributions to the advancement of science. He is best known for the four Maxwell equations, which he published in 1873. This mathematical formulation of Faraday's theories of electricity and lines of force is one of the great achievements of 19th century physics. Independently of Boltzmann he formulated a kinetic theory of gases where the behaviour was explained with probability analysis for a large number of particles. He also calculated that the rings of Saturn must consist of a large number of small particles and proposed that light is an electromagnetic phenomenon.
Meitner, Lise (1878-1968)
Austrian-born nuclear physicist who was the theoretical physics collaborator of Otto Hahn in the research that led to the discovery of nuclear fission. She named the process fission and in 1939, with her nephew Otto R. Frisch, she published a theoretical interpretation of Hahn's experiment. With Hahn she, in 1917, discovered the most stable isotope of protactinium, element 91. She also described internal conversion and (in 1923) the Auger effect. (Auger independently discovered the effect in 1925.) She also worked with the relation between beta and gamma rays. In 1907 she moved to Berlin but, because she was Jewish, she fled to Stockholm in 1938. In 1960 Meitner retired to live in England.
Newton, Isaac (1642-1727 according to the old style calendar, and 1643-1727 according to the Gregorian time)
Sir Isaac Newton is by many considered to be the single most important contributor to modern science. Several years before Leibniz he invented the differential and integral calculus, but he did not publish his results until after Leibniz had published his. Newton constructed the first reflecting telescope and worked out the mathematics of planetary motions. Halley persuaded Newton to publish his calculations, and in 1687 he published Philosophiae Naturalis Principia Mathematica, which probably is the most important and influential work on physics of all times. The first book of Principia explained Newton's three laws of motion. In the second book he stated explicit principles of scientific methods which applied universally to all branches of science, and in book three he proposed a universal gravitational force with which he could explain the causes of the tides and their major variations, the precession of the Earth's axis, and the motion of the moon and the planets. He also observed that white light from the sun changed into a spectrum of colours when the beam passed a glass prism. He believed that light consisted of small particles, or corpuscles, and that white light really was a mixture of different types of corpuscles. During his studies of optics he also observed Newton's rings. Newton retired 1693 after suffering a nervous breakdown. Opticks was published 1704, but the major research was done long before. It has been discovered that Newton had large amounts of mercury in his body, which is probably due to his alchemist experiments which from 1679 took a great part of his free time.
Pauli, Wolfgang (1900-1958)
Austrian theoretical physicist who was awarded the 1945 Nobel Prize for physics for his exclusion principle from 1925, which was a breakthrough in physics and chemistry that explained the structure of the periodic table of the elements in terms of the quantum theory. In 1931 he proposed the existence of a particle with no electrical charge and little or no mass. This particle, called a neutrino by Enrico Fermi, was finally observed in 1956. Following the outbreak of World War II he moved to the United States and became a US citizen in 1946. He later returned to Zürich. By many of his colleagues Pauli was looked upon as the archetype of a theorist, ignorant of practical matters. According to the "Pauli effect", stated by Gamow, all experiments self-destructed when Pauli was present in the laboratory.
Planck, Max (1858-1947)
German physicist who made significant contributions to optics, thermodynamics, statistical mechanics, physical chemistry, and other fields. In 1900 he published an equation which describes the blackbody spectrum. This equation, now called the Planck distribution, indicated that energy exists in discrete packages or quanta (E = hv), which makes Planck the originator of quantum physics. The full consequences of this revolutionary discovery was recognized many years later, and in 1918 he was awarded the Nobel Prize for physics. The fundamental constant h is now called the Planck constant. He lost his eldest son during World War I, and in 1945 his other son, Erwin, was executed for plotting to assassinate Hitler.
Röntgen, Wilhelm Conrad (1845-1923)
German physicist who in 1895 discovered X-rays, and for this he received the first Nobel Prize for physics in 1901. He demonstrated the medical and scientific use of X-rays, and this knowledge quickly spread throughout Europe and the United States.
Rutherford, Ernest (1871-1937)
New Zealand-born British physicist who established the nuclear model of the atom. He distinguished two kinds of radioactivity, which he called alpha and beta, and showed that alpha particles were doubly charged helium ions. He also coined the term 'half-life' of radioactive elements. In 1908 he received the Nobel Prize for chemistry (although he considered himself to be a physicist) for his investigations into the disintegration of the elements and the chemistry of radioactive substances. By bombarding metal foils with alpha particles Rutherford could in 1911 announce his version of the structure of the atom with a very small tightly packed and charged nucleus. In 1919 he was the first to artificially transmute one element into another. He bombarded nitrogen with alpha particles and found traces of hydrogen and oxygen.
Schrödinger, Erwin (1887-1961)
Austrian theoretical physicist who in 1926 invented wave mechanics, which is an alternative way, to Heisenberg's matrix mechanics, to formulate quantum mechanics. The central equation is now called the Schrödinger equation, which, in most cases, has turned out to be simpler to solve than Heisenberg's equations. In 1933 he shared the Nobel Prize for physics with Paul Dirac. From 1940 he was a professor at the Dublin Institute for Advanced Studies in Ireland. In 1956 he retired and returned to Vienna. Schrödinger published a collection of poems and the popular science book What is life?
Tesla, Nicola (1856-1943)
Inventor and electrical engineer who was granted more than 100 US patents. He was born i Croatia, he studied at the University of Prague and worked as an engineer in Budapest before he in 1884 moved to the United States to become a US citizen in 1889. He invented an AC power system with an efficient polyphase induction motor, far better than Edison's DC generators. He sold the patent to George Westinghouse for 1 million dollars + $1 per horsepower as royalty. With this money he founded the Tesla Electric Company and built his own laboratory. But his lab burnt to the ground in 1895 and everything was lost, because he had no insurance. He invented a high-frequency transformer, called the Tesla coil, which made AC power transmission practical. Tesla was highly eccentric and absolutely impractical with money. In the 1880s he quit working for Edison and when he found no other job he had to dig ditches for two years.
Volta, Alessandro (1745-1827)
Italian physicist who is best known for his invention from 1800 of the voltaic pile, the first electric battery. He used plates of copper and zinc separated by disks of cardboard moistened with a salt solution. He demonstrated his invention to Napoleon, who became so impressed that he appointed Volta a Count and Senator of Lombardy (a region in northern Italy). In 1775 he invented the electrophorus, a device that, once electrically charged by being rubbed, could transfer charge to other objects. He also discovered and isolated methane gas.
van der Waals, Johannes Diderik (1837-1923)
Dutch physicist who is best known for his work in physical chemistry. In 1910 he was awarded the Nobel Prize for physics for his research on gases and liquids which in 1873 led to the equation of state that has his name. With this law the existence of condensation and a critical temperature of gases could be predicted. In 1880 he formulated his "law of corresponding states" and in 1893 a theory for capillary phenomena. His equation of state assumes weak forces between molecules, now called "van der Waals forces".
Watt, James (1736-1819)
Scottish engineer and inventor who made several major improvements on the inefficient steam engine of his time. His first patent in 1779 was a chamber for condensing the steam. Although Watt did not invent the steam engine, his improved engine was really the first practical device for efficiently converting heat into useful work. This was a key stimulus to the Industrial Revolution. In 1774 Watt emigrated to England and by 1790 he had earned enough money to retire to his estate near Birmingham.