Niels Bohr (1885-1962), a Danish physicist, founded the modern quantum theory of matter. He is best known for his investigations of atomic structure and radiation, for which he won the 1922 Nobel Prize for physics.

Max Born (1882-1970), a German theoretical physicist, was a pioneer in developing quantum mechanics. In collaboration with his students and assistants Werner Heisenberg, Pascual Jordan, and Wolfgang Pauli, he attempted to develop a new quantum mechanics. When Heisenberg succeeded in 1925, Born and others were able to advance the theory, using more systematic and powerful mathematics. For Born's interpretation of the square of Schrodinger's wave function as the probability of an electron's position, and for his further clarification of the wave-particle duality, he was awarded the Nobel Prize for physics in 1954.

Nicolaus Copernicus (1473-1543) was the Polish astronomer who revolutionized science and the conception of the universe with his heliocentric theory of planetary movement, published as De revolutionibus orbium coelestium (1543).

Marie Curie (1867-1934), a French physicist, shown in her laboratory in a colored photograph taken in 1905, is best known for her work in the study of radioactivity. Together with her husband, Pierre, she shared the 1903 Nobel Prize for physics, and she received the prize for chemistry in 1911.

Louis de Broglie (1892-1987), a French physicist, is known for his theory that matter has the properties of both particles and waves. This particle-wave duality, derived from the work of Albert Einstein and Max Planck, was experimentally confirmed, for the electron, in 1927. De Broglie received the 1929 Nobel Prize for physics.

Paul Dirac (1902-1984) was awarded the 1933 Nobel Prize for physics for his modification of Schrodinger's wave equation, the mathematical theory describing the motion of atomic particles. Dirac, who shared the award with Schrodinger, applied relativity theory to quantum mechanics in predicting the existence of positrons and electron spin.

Albert Einstein (1879-1955), a German-American physicist, revolutionized the assumptions of modern physics when he first published his theory of relativity in 1905.

Michael Faraday (1791-1867), an English chemist and physicist, is shown here in an early daguerreotype holding a bar of glass he used in his 1845 experiments on the effects of a magnetic field on polarized light. Faraday is considered by many scientists to be the greatest experimentalist ever.

Enrico Fermi (1901-1954) conducted the experiments in radioactivity that won him the 1938 Nobel Prize for physics before emigrating from Italy to the United States and commencing work on the atomic bomb. An exceptional researcher and theorist, Fermi developed a statistical method for predicting the behavior of atomic particles and later led the group that achieved the first self-sustaining fission reaction.

Richard Phillips Feynman (1918-1988), an American physicist contributed to the joining of relativity and quantum theory with electromagnetism to form quantum electrodynamics. He is also known for his reformulation of quantum mechanics and his research on liquid helium. In 1965 he shared the Nobel Prize for physics with Julian Schwinger and Sin Itiro Tomonago for their contributions to electrodynamics.

Edmond Halley (1656-1742), an English astronomer and mathematician, is depicted in a 17th century colored engraving. Halley was the first to calculate the orbit of the comet that is named for him.

Stephen Hawking (1942- ), who has been paralyzed by Lou Gehrig's disease, is confined to a wheelchair and requires a voice synthesizer to speak. One of the world's top mathematical physicists, he has sought to link quantum mechanics and relativity, the two major theories of modern physics.

Werner Karl Heisenberg (1901-1976), a German theoretical physicist was one of the leading scientists of the 20th century. He did important work in nuclear and particle physics, but his most significant contribution was to the development of quantum mechanics. He is best known for his uncertainty principle, which restricts the accuracy with which some properties of atoms and particles--such as position and In 1932 he was awarded the Nobel Prize in physics.

Edwin Powell Hubble (1889-1953), an American astronomer and the founder of extragalactic astronomy, was a Rhodes scholar at Oxford and began his career as a lawyer. After a year of practicing law, he returned to graduate school and earned a doctorate in astronomy. His accomplishments include the discovery of galaxies beyond the Milky Way Galaxy and of the velocity-distance relationship of galaxies.

Lord Kelvin (1824-1907), a Scottish physicist and mathematician calculated that molecular motion stops at -273 deg C. He called this temperature absolute zero, the lowest possible temperature. A prodigy in mathematics, Kelvin gained his greatest renown in thermodynamics.

Johannes Kepler (1571-1630), a German mathematician, formulated the three laws of planetary motion that bear his name by using the astronomical observations of by Tycho Brahe, for whom he worked briefly. Kepler was instrumental in the development of early telescopes. He invented the convex eyepiece, which allowed an expanded field of vision, and discovered a means of determining the magnifying power of lenses.

Irving Langmuir (1881-1957), an American physical chemist, was awarded the Nobel Prize for chemistry in 1932 for his work on molecular films on solid and liquid surfaces. His studies in high-temperature chemistry led to the improvement of the tungsten-filament light bulb and the development of an atomic hydrogen blowtorch.

James Clerk Maxwell (1831-1879), the Scottish physicist, did revolutionary work in electromagnetism and the kinetic theory of gases. He formulated, independently of Ludwig Boltzmann, the Maxwell-Boltzmann kinetic theory of gases. Maxwell showed that a few relatively simple mathematical equations could express the behavior of electric and magnetic fields and their interrelated nature. These four partial differential equations first appeared in fully developed form in Electricity and Magnetism (1873). Since known as Maxwell's equations they are one of the great achievements of 19th-century physics.

Robert Andrews Millikan, b. Morrison (1868-1953), an American physicist, determined through an oil-drop experiment the value of the charge on an electron and demonstrated that the charge was a discrete constant rather than a statistical average. For this work, as well as for his work on the photoelectric effect, he received the Nobel Prize for physics in 1923.

Sir Isaac Newton (1643-1727), one of the most important figures in the history of science, made significant contributions in the fields of physics, astronomy, and mathematics. In his Principia (1687) -- considered by many the greatest work of modern science --he explained the laws of motion and universal gravitation.

Blaise Pascal (1623-1662), a French thinker. His early scientific investigations led to invaluable contributions in mathematics and physics. He is also remembered for his introspective religious and philosophical writings, most notably his Pensees, which focused on the power of divine faith.

Wolfgang Ernst Pauli (1900-1958), an Austrian theoretical physicist, was one of the founders of modern physics. He is most famous for his "Pauli exclusion principle," which states that no two electrons in an atom can have the same four quantum numbers. For his work in this area he was awarded the 1945 Nobel Prize for physics.

Max Planck (1858-1947), a German physicist, revolutionized physics in 1900 with his discovery of the quantum, or fundamental unit of energy. Planck received the Nobel Prize for physics in 1918 in recognition of his breakthrough. He is shown in a photograph taken in 1947, the year of his death.

Wilhelm Conrad Roentgen (1845-1923), a German physicist, received the first Nobel Prize for physics (1901) for his discovery of X rays.

Sir Ernest Rutherford (1871-1937) profoundly influenced modern physics by formulating the first explanation of radioactivity. He discovered two basic forms of radioactivity and in 1908 received the Nobel Prize for chemistry for this work. He announced his greatest discovery--the nuclear structure of the atom--in 1911.

Erwin Schrodinger (1887-1961), an Austrian theoretical physicist, published (1926) four papers that laid the foundation of the wave-mechanics approach to quantum theory and set forth his now-famous wave equation. In 1933 he shared the Nobel Prize for physics with Paul DIRAC for his contributions to atomic theory. He also worked on problems of general relativity and cosmology and on a unified field theory. Late in his life Schrodinger studied the foundations of physics and their implications for philosophy.

Sir Joseph John Thomson (1856-1940), a pioneer in modern physics, discovered the electron in 1895, revolutionizing existing theories of atomic structure. Thomson is also recognized for his investigations into the conduction of electricity through gases--which earned him the 1906 Nobel Prize for physics--and for his work on the mathematics of the electromagnetic-field theory proposed by James Maxwell.

Hideki Yukawa (1907-1981), a Japanese physicist, who won the Nobel Prize for physics in 1949, is known for his theory of how the nuclear force holds the nucleus together. As a result of this theory, he predicted (1935) the existence of the meson, a subatomic particle, found in 1947 by Cecil Powell.