Japanese physicist Tomonaga Shin’ichiro won the 1965 Nobel Prize in physics. His work explored the electrodynamic properties of atomic particles.
Shin’ichiro Tomonaga (1906-1979), Japanese physicist and Nobel Prize winner. Tomonaga took an important step for quantum electrodynamics by making mathematical predictions that were consistent with observed physical phenomena of the special theory of relativity. For this work, he shared the 1965 Nobel Prize in physics with American physicists Julian Seymour Schwinger and Richard Phillips Feynman.
Born in Tokyo, Tomonaga became interested in physics after learning about American physicist Albert Einstein's well-publicized visit to Japan in 1922 and reading a book on relativity theory. He earned his B.S. degree in physics from Kyoto Imperial University in 1929. During his final year at Kyoto, Tomonaga studied quantum mechanics without the help of a professor. After graduating, he stayed on at Kyoto as an unpaid research assistant. In 1932 Tomonaga joined fellow researcher Yoshio Nishina at the Institute for Physical and Chemical Research to do theoretical and experimental work in nuclear physics. Tomonaga studied in Germany from 1937 to 1939 with German physicist Werner Heisenberg at the University of Leipzig. He then returned to Japan to obtain his Ph.D. degree in physics (1939) from Tokyo Imperial University (later renamed Tokyo University), where he later became a professor, a position he held until 1970.
During World War II (1939-1945), Tomonaga performed military research for the Japanese Navy and worked on theories of quantum electrodynamics. Earlier work by British physicist Paul Dirac applied quantum mechanics to an analysis of the electromagnetic field. Dirac predicted that particles such as the electron could have an infinite quantity of energy, which led to other predictions that contradicted experimental observations. Tomonaga reworked Dirac's mathematics in the theory so that those infinite quantities no longer appeared. This adjustment made Dirac's theory consistent with observation, and permitted physicists to predict the magnetic and other properties of particles and radiation. The renormalized theory of quantum electrodynamics has proved to be amazingly accurate, even with increasingly sophisticated and sensitive experimental equipment. Schwinger and Feynman also modified Dirac's theory. All three physicists worked independently of each other, but Schwinger and Tomonaga approached the problem in much the same way, while Feynman's method was very different.
After performing his groundbreaking research in quantum electrodynamics, Tomonaga worked in the areas of quantum dynamics, the theory of neutrons, and electromagnetics. He also became increasingly involved in scientific administration, serving as a member, and later president, of the Science Council of Japan in 1951. From 1957 on, he was active in movements against the deployment of nuclear weapons.
Leo Esaki, born in 1925, Japanese physicist whose groundbreaking work on semiconductors earned him a Nobel Prize in 1973. Esaki proved the concept of tunneling in semiconductors and developed the tunnel diode, also known as the Esaki diode. In classical physics, an electric current cannot flow in a circuit interrupted by an insulating barrier—that is, when electrons reach the “wall” of insulating material, they cannot continue forward. Since the 1930s, quantum mechanics, the branch of physics that studies the motion of subatomic particles and related phenomena, had predicted that electrons might be able to “tunnel” through an insulating barrier if it were thin enough. Esaki developed a diode with electrical junctions only 10 billionths of a meter thick through which electrons could tunnel. Esaki shared the Nobel Prize with Norwegian-born American physicist Ivar Giaever and American physicist Brian D. Josephson.
Esaki was born in Osaka, Japan. He attended the University of Tokyo, where he earned a B.S. degree (1946), an M.S. degree (1947), and a Ph.D. degree (1959) in physics. While studying for his doctorate, he worked in Tokyo at Kobe Kogyo Corporation and Sony Corporation. His discovery of tunneling occurred at Sony in 1957 while he was still a student. Esaki moved to the United States in 1960 to join the Thomas J. Watson Research Center at IBM in New York. His research focused on semiconductor physics. He was made an IBM fellow, the company's highest research position, in 1965. He began work in superlattices as part of an effort to demonstrate other predicted but unproven theories of quantum mechanics. Superlattices are synthetic crystals composed of extremely fine layers of different semiconductors. One of the potential uses for this material is in high-speed computers. Esaki stayed at IBM for 33 years, eventually becoming a director of the company. During this period, he also lectured at the University of Pennsylvania and the University of Tokyo. When he retired from IBM in 1993, Esaki returned to Japan. Since then he has served as president of Tsukuba University.
Charles T. R. Wilson (1869-1959), Scottish physicist and Nobel laureate. Wilson invented the cloud chamber (see Particle Detectors), which gave the first pictures of the paths of subatomic particles (see Elementary Particles) and became an essential tool in the fields of atomic and meteorological physics (see Atom; Meteorology). For his discovery of the method of making the paths of electrically charged particles visible by the condensation of water vapor, Wilson shared the 1927 Nobel Prize in physics with American physicist Arthur Holly Compton.
Wilson was born in Glencorse in the former county of Midlothian, Scotland. He received a B.S. degree from Owens College (now the Victoria Institute of Manchester) in England in 1887 and a B.A. degree from the University of Cambridge in 1892. After teaching at Bradford Grammar School in Bradford, England, for four years Wilson returned to Cambridge in 1896 as a researcher and remained there, eventually as a professor, until he retired in 1936. He remained active in research, publishing his last paper at the age of 87.
Wilson first developed the cloud chamber in the late 1890s to study how water vapor and light interact. Physicists at that time thought that water droplets formed only around dust particles. Wilson established that water droplets can form around charged particles, or ions, in the absence of dust. He found that if he exposed the air in a chamber to X rays, many more droplets formed. He concluded the X rays give the air molecules an electrical charge, or ionize them.
As an ion moves through the cloud chamber, drops of water form around it. Because the ion moves very quickly, the string of drops of water in the air looks like a continuous path marking the movement of the ion. The path is especially apparent when a strong light is directed at the cloud chamber. If a magnetic field (see Magnetism) is applied to the cloud chamber, the ions will follow curved paths depending on the strength and nature of the charge, the mass of the ion, and the strength and direction of the magnetic field. The paths can be photographed for later analysis.
Wilson also intensely studied electrical conduction in air and applied his findings to devising ways to protect British airships from lightning and other discharges of electricity during World War I (1914-1918).
David Brewster (1781-1868), Scottish physicist, who discovered that light is polarized by reflection. He also invented the kaleidoscope.
Born in Jedburgh, Roxburghshire, Brewster studied for the ministry and served as a Presbyterian minister into his early 20s. He then left the clergy to pursue the study of science. While editor of the Edinburgh Encyclopedia, Brewster studied the properties of reflected, absorbed, and polarized light.
In 1815 Brewster observed that when a nonmetallic surface reflects light, partial polarization occurs, meaning that some of the light waves orient themselves in the same plane (see Optics: Polarization of Light). He also found that polarization increases as the angle of light rays becomes more of a glancing angle. Polarization eventually reaches the maximum point, known as the Brewster angle, and then decreases.
In addition to making microscopes and other optical devices, Brewster invented the kaleidoscope—a scientific toy that continues to entertain both children and adults. He devised the kaleidoscope in 1816 and then patented it, but even though thousands were sold in a short time, he ultimately earned nothing from it since it was an easy invention to copy. Brewster also invented the stereoscope, through which a viewer sees two slightly different pictures, one with each eye. The effect creates a three-dimensional illusion.
In 1819 Brewster was awarded the Rumford Medal by the Royal Society of London for his work with polarized light. He helped found the British Association for the Advancement of Science in 1831, and he was knighted in 1832. His books include Treatise on Optics (1831) and Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton (1855).
Dyson's research began at an important time in the study of physics. During the years just after World War II (1939-1945), new experimental evidence raised questions about how quantum theory, developed during the 1920s and 1930s to describe the relationships between electrons and atomic nuclei, might be extended to cover the interactions of matter and light. But the mathematical techniques used to extend quantum theory had internal difficulties that led to seemingly absurd results. However, about 1949 two dominant, and seemingly unrelated, theoretical solutions to these mathematical problems emerged: one theory was developed by the American physicist Richard P. Feynman, and the other was developed by the American physicist Julian S. Schwinger and independently by the Japanese physicist Tomonaga Shin’ichiro. About 1950 Dyson showed that both theories were reducible to a single formalism, and he became a major figure in the application of these ideas. The resulting theory and the mathematical techniques associated with it became central to modern theoretical physics during the second half of the 20th century.
Since the time he was a student Dyson has been interested in the military applications of physics and the peaceful applications of nuclear energy. His books that discuss nuclear strategy and arms control include his autobiography, Disturbing the Universe (1979), and Weapons and Hope (1984).
German-born American physicist Hans Georg Dehmelt won the Nobel Prize in physics in 1989. Dehmelt developed techniques for isolating and studying individual atoms and particles.
Hans Georg Dehmelt, born in 1922, German American physicist and Nobel Prize winner. Dehmelt is noted for developing techniques for isolating and studying individual atoms and particles, enabling researchers to better study fundamental atomic properties. For this work, he shared the 1989 Nobel Prize in physics with German physicist Wolfgang Paul and American physicist Norman Foster Ramsey.
Born in Görlitz, Germany, Dehmelt earned his Ph.D. degree in 1950 at the University of Göttingen. He was a research fellow for several years at Hans Kopfermann's Institute in Göttingen. In 1952 Dehmelt went to the United States, where he conducted research at Duke University. In 1955 he joined the faculty of the University of Washington, where he continues his research and teaching.
Building on the work of Wolfgang Paul, Dehmelt experimented with a three-dimensional electric field (the Paul trap) to suspend ions in a small area. By adding a strong magnetic field to the device, Dehmelt in 1973 was able to isolate and store a single electron. He used this device, called a Penning trap, to study the magnetic properties and spin states of electrons. Dehmelt also developed a technique to cool the particles being studied to slow down their movement, which improved the accuracy of the measurements being taken. These measurements proved to be so precise that they provided verification of fundamental theories in quantum theory (the science relating to mass and electromagnetic radiation in atoms).
Dehmelt continued to perfect his techniques for studying atomic particles. He improved the accuracy of his magnetic measurements in electrons, achieving an accuracy of just a few parts in a trillion. In 1980 he successfully isolated, cooled, and photographed a single ion in the Penning trap. Numerous other researchers have put this technique to use in studying the mass of atoms and atomic particles.
Dutch-American theoretical physicist Peter Joseph Wilhelm Debye won the 1936 Nobel Prize in chemistry. He studied molecular structure, dipole movements, and X-ray and electron diffraction in gases.
Peter Joseph Wilhelm Debye (1884-1966), Dutch-American theoretical physicist, who received the 1936 Nobel Prize in chemistry for his studies in molecular structure, dipole movements, and the diffraction of X rays and electrons in gases.
Debye was born in Maastricht, March 24, 1884, and educated at the University of Munich. From 1911 to 1935 he held the post of professor of physics successively at several universities in Switzerland, the Netherlands, and Germany. He then became director of the Kaiser Wilhelm Institute for Physics in Berlin. In the U.S., he served as professor of chemistry at Cornell University from 1940 to 1952; in 1952 he became professor emeritus. He died at Ithaca, New York, on November 2, 1966.
In 1912 Debye modified the specific-heat theory put forth by Albert Einstein by calculating the probability of any frequency of molecular vibration up to a maximum frequency; the theory of specific heat constituted one of the earliest theoretical successes of the quantum theory. Debye also applied the quantum theory to explain the heat conductivity of crystals at low temperature, the variation of saturation intensity of magnetization with temperature, the theory of space quantization (with the German physicist Arnold Sommerfeld, 1868-1951), and the phenomena of scattering of X rays (with the American physicist Arthur Holly Compton). In 1923 Debye developed a theory of ionization of electrolytes (now called the Debye-Hückel theory), which is important in chemistry (see Ionization). Later he worked on the theory of quantum mechanics, including its applications to the diffraction of electrons in gases. In 1963 he was awarded the Priestley Medal by the American Chemical Society.
Among Debye's writings are Quantum Theory and Chemistry (1928), Polar Molecules (1929), and Molecule Structure (1931).
American physicist Clinton Joseph Davisson won the Nobel Prize in physics in 1937. Davisson found that electrons could be diffracted by crystals just like X rays. He also proved they can show wavelike structure.
Clinton J. Davisson (1881-1958), American physicist and Nobel laureate. Davisson made major contributions to understanding the diffraction of electrons by crystals and shared the 1937 Nobel Prize in physics with British physicist Sir George Paget Thomson for their independent proof of the wave properties of electrons.
Born in Bloomington, Illinois, Davisson entered the University of Chicago in 1902. He left to teach physics at Purdue University in 1903 and 1904. In 1905 he became a physics instructor and research assistant at Princeton University. Returning to the University of Chicago for summer sessions, Davisson finally completed his B.S. degree in physics in 1908. After earning a Ph.D. degree in physics from Princeton University in 1911, Davisson accepted an appointment as an assistant professor of physics at the Carnegie Institute of Technology.
In 1917, during World War I (1914-1918), Davisson took leave from the Carnegie Institute to work on a military telecommunications project at the engineering department of the Western Electric Company Laboratories, which later became the Bell Telephone Laboratories. After the war, he decided to remain at the laboratories, which guaranteed him freedom to do full-time research, an uncommon opportunity in commercial laboratories at that time. Davisson retired from Bell in 1946 and accepted a position as a visiting professor of physics at the University of Virginia in Charlottesville, where he remained until his retirement in 1954.
At Western Electric, Davisson pursued his interest in thermionics, the emission of electrically charged particles, or ions, from conducting materials such as metals heated to high temperatures. His experiments in thermionics revised classic theory on conduction and the thermal energy of electrons.
In 1925 an accidental explosion of a bottle of liquid air (air that has been cooled and compressed until it becomes a liquid; see Matter, States of) in Davisson's laboratory put him on the path to a great discovery. The explosion allowed a piece of nickel Davisson was using as a target for high-speed electrons to become oxidized—that is, for the outer nickel atoms to bond with oxygen atoms (see Chemical Reaction). After cleaning the target by means of prolonged heating, Davisson found that although it had originally been composed of many small crystals, it had now formed several large crystals. He continued with the experiment but found that the electrons that now bounced off the target were bouncing off at completely different angles than before. Davisson attributed the change only to the different way the target was reflecting the electrons, but a 1926 meeting of physicists convinced him to search for a further cause. There he first learned in detail about the hypothesis of French physicist Louis de Broglie that any material particle (see Matter) could behave like a wave (see Wave Motion). Joining forces in 1926 with American physicist Lester Halbert Germer, Davisson searched for evidence of interference—that is, the effects resulting from adding waves together—between the electrons as they bounced off the target; an interference pattern would be present only if the electrons were behaving like waves—purely material particles cannot produce interference patterns.
In 1927 Davisson showed that, like electromagnetic waves (see Electromagnetic Radiation), electrons can produce interference patterns and be diffracted by crystals. His experiments proved that electrons can show wavelike behavior and helped show that all matter can show wavelike behavior since electrons are one of the subatomic particles that make up all matter. For this discovery, Davisson was awarded the Comstock Prize of the National Academy of Sciences in 1928.
In the 1930s Davisson's research continued to focus on electron waves, especially in their application to crystal physics and electron microscopy (see Microscope), and helped to develop a technique for electron focusing. Davisson's later research focused on the theory and application of electron optics, the theory of electronic devices (see Electronics), and solid-state physics, also known as condensed-matter physics.
American physicist James Cronin won the 1980 Nobel Prize in physics for demonstrating the changes that occur when matter transforms into antimatter.
James W. Cronin, born in 1931, American physicist and Nobel laureate. Cronin shared the 1980 Nobel Prize for physics with American Val Logsdon Fitch for demonstrating that, unlike what was previously thought, symmetry is not always preserved when some elementary particles change in state from matter to antimatter.
Cronin was born in Chicago, Illinois, and received his bachelor's degree at Southern Methodist University in 1951. He earned both his master's and doctoral degrees in 1955 in physics from the University of Chicago. From 1955 to 1958 Cronin served as an assistant physicist at Brookhaven National Laboratory in Long Island, New York. He taught at Princeton University from 1958 to 1971 and in 1971, Cronin became professor of physics at the University of Chicago.
In 1964, Cronin, Fitch, and some of their colleagues were studying a subatomic particle called the K. meson, also known as a kaon. A meson is a particle that weighs approximately half as much as a proton. The kaon is an unstable, neutral (uncharged) meson that had been discovered in the interactions between particles from outer space and particles from the earth's atmosphere.
Physicists thought for some time that the universe followed three fundamental rules of symmetry. The first, the symmetry of charge conjugation (C), states that the result of an experiment should not change if all the particles in the experiment are switched from antimatter to matter or vice versa. The second rule of symmetry, parity (P), says that the result of an experiment should not change if the positions of all the particles in the experiment are completely reversed. The third rule, time-reversal (T), says that any reaction between elementary particles should occur equally well in either direction; that is, if two particles can come together to form one particle, the resulting particle should be able to decay to form the original two particles.
Before Cronin and Fitch started their experiment, the rules C and P had both been found to be untrue in some cases. Physicists tried to preserve the idea of symmetry by theorizing that any reaction had to be symmetric over a combination of CP; that is, if C symmetry was violated, P symmetry would have to be violated, too. Cronin and Fitch disproved this rule by showing that kaons do not preserve P, C, or CP symmetry some of the time. However, one rule of symmetry remains above suspicion: all reactions must be symmetric in the combination of charge conjugation, parity, and time (CPT).
Since every reaction has to be symmetric under CPT, Cronin and Fitch's result showed that T symmetry has to fail when CP symmetry fails. That means reactions that do not preserve CP symmetry cannot run backward. Some scientists think this explains how more matter than antimatter is created in the universe.
American physicist Leon Cooper won the Nobel Prize in physics in 1972. Cooper developed a theory of why some metals can be superconductive.
Leon N. Cooper, born in 1930, American physicist, professor, and Nobel Prize winner. Cooper contributed significantly to the development of a theory of superconductivity by discovering what are now called “Cooper pairs”—that is, two electrons that, when situated a certain way among positive ions, no longer repel each other but instead develop an attraction for each other. These pairs then accumulate and move in the same direction; the result is a superconducting metal because there is no resistance to the flow of electricity through the metal. For his work in superconductivity, Cooper shared the 1972 Nobel Prize in physics with fellow American scientists John Bardeen and J. Robert Schrieffer.
Cooper was born in New York City. As a high school senior, he entered the Westinghouse Science Talent Search competition with a research project that analyzed how certain bacteria can become penicillin resistant. For his efforts, he was selected as one of 40 national winners. In 1954 Cooper received a Ph.D. degree in physics from Columbia University. His dissertation was supervised by American physicist J. Robert Oppenheimer, who had directed the development of the atomic bomb.
In 1955 Cooper was working on quantum field theory at the Institute for Advanced Study in Princeton, New Jersey, when John Bardeen, a scientist at the University of Illinois, invited Cooper to study superconductivity with him. First discovered in 1911, superconductivity is a phenomenon in which certain metals, when cooled to a temperature that is near absolute zero, no longer resist a flow of electricity running through them. The resulting free flow of electrons in the metal results in increased conductivity—an important discovery, particularly for the electronics industry. Electrical devices can waste large amounts of energy simply in trying to overcome electrical resistance, a problem that could be virtually eliminated if superconducting materials were used instead.
But for years after the discovery of superconductivity, scientists encountered difficulty when trying to apply the phenomenon in practical ways because of the extremely low temperature to which the metals must be cooled in order to overcome the electrical resistance. From 1955 to 1957 Bardeen, Cooper, and another physicist, J. Robert Schrieffer, developed what would later become known as the BCS theory of superconductivity, which explains why certain materials can be superconductive.
In 1957 Cooper left the University of Illinois to become an assistant professor of physics at Ohio State University. Since 1958 he has taught physics at Brown University in Providence, Rhode Island. Cooper holds honorary degrees from several United States universities and has received many awards for his work. In recent years, he has devoted his efforts toward a better understanding of memory and other brain functions.
Edward U. Condon (1902-1974), American physicist, noted for his work in quantum theory, nuclear reactions, and the spectra of atoms and molecules. He was born in Alamagordo, New Mexico, and educated at the University of California at Berkeley. From 1928 to 1937 he taught physics at Princeton University. He was one of the early supporters of the atomic bomb program. Between 1943 and 1945 he worked at the University of California on the electromagnetic separation of uranium-235. He became professor of physics and fellow of the Joint Institute for Laboratory Astrophysics at the University of Colorado in 1963. Between 1966 and 1969 he was also a scientific director of the government-financed investigation of unidentified flying objects.
American physicist Arthur Holly Compton won the Nobel Prize in physics in 1927. Compton confirmed that radiation has both particle and wave characteristics
Arthur Compton (1892-1962), American physicist and Nobel laureate whose studies of X rays led to his discovery in 1922 of the so-called Compton effect. The Compton effect is the change in wavelength of high energy electromagnetic radiation when it scatters off electrons. The discovery of the Compton effect confirmed that electromagnetic radiation has both wave and particle properties, a central principle of quantum theory.
Arthur Holly Compton was born in Wooster, Ohio, and educated at Wooster College and Princeton University. In 1923 he became professor of physics at the University of Chicago. While at the University of Chicago, Compton directed the laboratory where the first sustainable nuclear chain-reaction was performed. (see Nuclear Energy). Compton also played a role in the development of the atomic bomb (see Nuclear Weapons). From 1945 to 1953 Compton was chancellor of Washington University, and after 1954 he was professor of natural philosophy there. For his discovery of the Compton effect and for his investigation of cosmic rays and of the reflection, polarization, and spectra of X rays, he shared the 1927 Nobel Prize in physics with the British physicist Charles Wilson.
French physicist Claude Cohen-Tannoudji shared the 1997 Nobel Prize in physics with two other physicists. All three physicists were recognized for their individual work in cooling and trapping atoms
Claude Cohen-Tannoudji, born in 1933, French physicist and Nobel laureate. Cohen-Tannoudji pioneered research into cooling, slowing, and trapping atoms—one of the basic building blocks of matter—with special beams of light called lasers (see Particle Trap). The techniques Cohen-Tannoudji and others developed led to significant advancements in the study and manipulation of atoms, resulting in many applications. These applications include more accurate atomic clocks and more precise devices for measuring gravity. He shared the 1997 Nobel Prize for physics with two American scientists who were also successful in slowing atoms, Steven Chu and William D. Philips. The three didn’t work side by side; yet each contributed to and built upon the work of the other two.
Born in Constantine, Algeria, Cohen-Tannoudji earned his undergraduate degree in 1957 and his Ph.D. degree in 1962 in physics from École Normale Supérieure (ENS) in Paris, France. As a student at ENS he worked under the direction of French physicist Alfred Kastler, who won the Nobel Prize in physics in 1966, and Jean Brossel, another noted French physicist. Cohen-Tannoudji remained a researcher at ENS throughout his career. He was instrumental in the creation of a research center devoted to atomic physics and optics. The center is named the Kastler-Brossel Laboratory, after his two professors.
Cohen-Tannoudji joined the Centre National de la Recherche Scientifique (CNRS) in 1960. In 1973, while still associated with CNRS, he began a lengthy stint as chair of atomic and molecular physics at the Collége de France in Paris.
As a student, researcher, and professor, Cohen-Tannoudji became an expert in the field of slowing atoms. At room temperature, atoms move at speeds of about 4000 km/h (about 2500 mph), too fast for scientists to study them thoroughly. Heat results from atomic motion, so slowing atoms down lowers their temperature. Cohen-Tannoudji was among the first to propose using lasers to slow down atoms. The concept involves bombarding the atoms with laser light. Packets of light wave energy called photons strike the atoms in a way that is roughly the same as raindrops hitting a beach ball. Even though the photons have no mass, they move fast enough (at the speed of light) to produce enough momentum to slow the atoms with their impacts.
In 1985 Steven Chu and his team cooled atoms to 240 millionths of a Celsius degree (430 millionths of a Fahrenheit degree) above absolute zero (-273.15° C, or -459.67° F), which slowed atoms to about 0.5 km/h (0.3 mph). By 1988 William D. Philips and his research team had cooled atoms to 40 millionths of a Celsius degree (70 millionths of a Fahrenheit degree) above absolute zero, which was below the temperature that was believed to be theoretically possible at the time. In 1995 Cohen-Tannoudji and his team achieved a temperature of 0.2 millionths of a Celsius degree (0.4 millionths of a Fahrenheit degree) above absolute zero. Through his career Cohen-Tannoudji developed several cooling mechanisms used to trap atoms.
Manipulating atoms and studying them more closely allows scientists to improve many areas of technology. In an atomic clock, the more control the mechanism has over the atoms that it uses to keep track of time, the more accurate it can be. Increasingly accurate atomic clocks improve space navigation and global positioning systems that rely on the clocks. Trapped atoms are also useful in measuring the force of gravity of a particular spot on the earth. Changes in the gravitational field of the earth from place to place indicate changes in the density of the earth, which can lead scientists to oil and other valuable deposits within the earth. The ability to control atoms also raises the possibility of using atoms to etch electronic circuits. This would increase the circuits’ capabilities by making the circuits finer, and each area of circuit board would be able to hold more circuits.
In 1996 Cohen-Tannoudji won CNRS’s gold medal. In 1997, along with former students Jacques Dupont-Roc and Gilbert Grynberg, he wrote the book Introduction to Quantum Electrodynamics.
American physicist Steven Chu shared the 1997 Nobel Prize in physics with two other researchers. Chu was honored for his work in cooling and trapping atoms and other small particles.
Steven Chu, born in 1948, American physicist and Nobel laureate. Chu led a team of physicists in the mid-1980s who were the first to trap atoms (one of the basic units of matter) with special beams of light called lasers. These laser traps (see Particle Trap: Neutral Particle Traps) allow scientists to study atoms more closely and use atoms more efficiently in devices such as atomic clocks. Chu’s research helped pave the way for important discoveries in atomic physics. It also led to the development of many new practical applications, including more accurate atomic clocks and more precise devices for measuring the pull of gravity. He shared the 1997 Nobel Prize for physics with two other researchers who made separate and complementary advancements in the field, French physicist Claude Cohen-Tannoudji and American physicist William D. Philips.
Chu was born in St. Louis, Missouri, and grew up on Long Island, New York. He earned dual undergraduate degrees in physics and mathematics at the University of Rochester in New York in 1970. In 1976 he received his doctoral degree in physics from the University of California, Berkeley. Chu spent two years conducting post-doctoral research at Berkeley, then served as a member of the technical staff of American Telephone and Telegraph (AT&T) from 1978 to 1983.
In 1983 Chu was named head of the quantum electronics research department at AT&T’s Bell Laboratories and moved to the lab’s complex in Holmdel, New Jersey. That year he began discussing the possibility of trapping atoms with American physicist Arthur Ashkin. Over the next few years, Chu, Ashkin, and fellow American physicists John Bjorkholm and Alex Cable conducted experiments in which six lasers bombarded atoms from six sides in a vacuum chamber at Chu’s lab.
At room temperature, atoms move at speeds of about 4000 km/h (2500 mph), much too fast for scientists to easily study them. The speed of atoms is related to their temperature—atoms at a higher temperature move faster than cooler atoms. Slowing a sample of atoms will therefore make the atoms cooler. Chu pioneered a technique for slowing and cooling atoms that uses lasers to immerse the atoms in photons (packets of light wave energy). The photons strike the atoms in a way that is roughly analogous to raindrops hitting a beach ball. The photons have no mass, but because they move at the speed of light, they carry momentum and can affect a small mass, such as an atom. In Chu’s trap, the impact of enough photons hitting atoms slowed the atoms down. The atoms moved so slowly that they seemed to be stuck, so Chu’s team named the process “optical molasses.”
In 1985 Chu and his team cooled atoms to 240 millionths of a Celsius degree (430 millionths of a Fahrenheit degree) above absolute zero, the point at which all matter stops moving (–273.15° C, or -459.67° F). By 1988 William D. Philips and his research team had cooled atoms to 40 millionths of a Celsius degree (70 millionths of a Fahrenheit degree) above absolute zero, which was lower than scientists believed to be theoretically possible at the time. Claude Cohen-Tannoudji and his team achieved a temperature of 0.2 millionths of a Celsius degree (0.4 millionths of a Fahrenheit degree) above absolute zero in 1995.
The ability to manipulate atoms and study them more closely led to many real and potential applications, including increased accuracy in atomic clocks, which improved their use in space navigation and global positioning systems. Atomic clocks keep track of time by counting waves of radiation emitted by special atoms in traps inside the clock. If the traps can hold the atoms at lower temperatures, the traps and mechanisms inside the clock can exercise more control over the atom, reducing the possibility of error. Atom manipulation also contributes to increased accuracy of the measurement of gravitational force, which is useful in, among other things, oil exploration. This is because a deposit of oil or other substance beneath the earth’s crust has a different density from the areas around it. Changes in density produce changes in the local gravitational field, because the gravitational force of an area is related to the mass of that area. Advances in the manipulation of atoms have also raised the possibility of using atoms to etch electronic circuits, thereby increasing the circuits’ capabilities.
In 1987 Chu joined the faculty at Stanford University as a professor of physics and applied physics. While at Stanford, he and his colleagues continued the study of cooled atoms. In 1992 Chu was named a fellow of the American Academy of Arts and Sciences and a year later a member of the National Academy of Sciences.
Indian-born American theoretical astrophysicist Subrahmanyan Chandrasekhar won the 1983 Nobel Prize in physics. He studied the process by which stars evolve.
Subrahmanyan Chandrasekhar (1910-1995), American theoretical astrophysicist and Nobel laureate, who contributed greatly to the current understanding of stellar evolution. He was born in Lahore, India (now Pakistan), and was educated in India and at Trinity College and the University of Cambridge, earning a Ph.D. in 1933. In 1953 he became a U.S. citizen.
Although Chandrasekhar worked on theories of radiative transfer and convective transport of heat in stellar atmospheres, his most important studies concerned the small, dim, hot, dense stars known as white dwarfs (see Star). He determined that a star with a mass more than 1.44 times that of the mass of the Sun cannot directly become a white dwarf, a limit now called the Chandrasekhar limit. He shared the Nobel Prize in physics in 1983 with U.S. physicist William Fowler for his work on stars. His books include An Introduction to the Study of Stellar Structure (1939) and Principles of Steller Dynamics (1942). The Chandra X-ray Observatory, a powerful X-ray telescope named after Chandrasekhar, was launched by the United States into Earth’s orbit from a space shuttle in 1999.
American physicist Owen Chamberlain won the Nobel Prize in physics in 1992. Chamberlain confirmed the existence of the antiproton, a form of antimatter
Owen Chamberlain (1920-2006), American physicist and Nobel laureate. For their collaborative discovery of the antiproton (see Proton), Chamberlain and Italian-born American physicist Emilio Gino Segrè shared the 1959 Nobel Prize in physics.
Born in San Francisco, California, Chamberlain completed his undergraduate studies at Dartmouth College, receiving a B.S. degree in physics in 1941. From 1942 to 1946 he served as a researcher on the Manhattan Project, which developed the atomic bomb (see Nuclear Weapons) during World War II (1939-1945). From 1947 to 1949 he worked at the Argonne National Laboratory near Chicago, Illinois, obtaining a Ph.D. degree in physics at the University of Chicago in 1949. He then joined the faculty of the University of California at Berkeley, becoming a professor of physics in 1958, a position he held until his retirement in 1989.
Chamberlain's work in nuclear physics began with close investigation of subatomic particles, or particles that make up atoms (see Elementary Particles). His part in the atomic-bomb project led him to study alpha-particle decay, neutron diffraction, and high-energy nuclear reactions (see Nuclear Chemistry; Nuclear Energy). In 1955 Chamberlain, with Emilio Segrè, discovered the antiproton, a form of antimatter. Later Chamberlain also confirmed the existence of the antineutron.
Chester Carlson (1906-1968), American physicist, patent attorney, and inventor of xerography, an electronic dry-copying process for the reproduction of images or documents, commonly known now as photocopying.
Born in Seattle, Washington, Chester Floyd Carlson worked for a printer before studying physics at the California Institute of Technology. After graduating in 1930, he worked for a short time for the Bell Telephone Company, earned a law degree, and took a position in the patent department of an electronics firm in New York City. Carlson found it difficult to get copies of patent drawings, so in his spare time he searched for a cheap, dry method of copying documents, specifically printed or drawn matter. He developed a process that used electrostatic attraction to cause powder to adhere to plain paper, making his first successful copy on October 22, 1938. Because the process used no ink, Carlson called the technique xerography, from the Greek words meaning “dry writing.” This process is now known as photocopying.
In this process a plate coated with a light-sensitive material, such as selenium, is given a positive electric charge, and a powder, called toner, is given a negative electric charge. The toner and plate are therefore attracted to each other. Light is reflected from the original document through a lens onto the plate, and when the toner is applied to the plate, it clings to those places where light has not penetrated and destroyed the charge. In other words, the toner clings to the shadows cast by the opaque printing of the object copied. Paper is applied to the plate, and the image is transferred. Heat then fixes the toner on the paper, completing the copy. Photocopying is quick and involves no moisture—and thus it produces little mess. A variation of the process, known as xeroradiography, is used in the production of X-ray images.
Although his invention would eventually become the worldwide standard for copying, Carlson spent years securing a patent. He also had trouble finding a company willing to market the process. Finally, in 1947, the Haloid Company of Rochester, New York, obtained the rights to his invention. Working with the company, which changed its name to the Xerox Corporation, Carlson significantly refined copying for office use. In 1959 the Xerox Corporation introduced the first automatic copier.
American physicist Percy Bridgman won the Nobel Prize in physics in 1946. Bridgman studied the properties of materials under high pressure and made it possible to synthesize diamonds.
Percy Williams Bridgman (1882-1961), American physicist and Nobel laureate, who was noted for his study of the behavior of materials at high pressure. Bridgman was born in Cambridge, Massachusetts, and educated at Harvard University. He joined the physics department of Harvard in 1910 and was appointed a full professor in 1919.
In his study of high-pressure phenomena, Bridgman was often forced to develop his own experimental equipment. Eventually he was able to create pressures as high as 400,000 atmospheres. Bridgman did experiments that explored the mechanical and thermodynamic properties of materials at high pressure (see Thermodynamics). In addition to the scientific discoveries he made using his equipment, the techniques he developed enabled others to make important advances in high-pressure science and engineering, such as the ability to synthesize diamonds, which was first done in 1955. Bridgman received the 1946 Nobel Prize in physics for the development of his experimental apparatus, and for the discoveries he made using that apparatus. Bridgman is also known for his writings on the conceptual foundations of physics. Among his works in this area are The Logic of Modern Physics (1927) and The Way Things Are (1959).
American physicist Walter Houser Brattain won the Nobel Prize in physics in 1956. Brattain worked on the team that developed the transistor and the semiconductor.
Walter Houser Brattain (1902-87), American physicist and Nobel laureate, born in Xiamen (Amoy), China. After working as a physicist in the radio division of the National Institute of Standards and Technology, in 1929 he joined the staff of Bell Telephone Laboratories. While working at Bell, Brattain and the American physicists William Shockley and John Bardeen developed a small electronic device called the transistor. First announced in 1948, the transistor was perfected by 1952 for commercial use in portable radios, hearing aids, and other devices. For his work on semiconductors and discovery of the transistor effect, Brattain shared the 1956 Nobel Prize in physics with Shockley and Bardeen.
Dutch-American physicist Nicolaas Bloembergen won the Nobel Prize in physics in 1952. Bloembergen developed laser spectroscopy.
Nicolaas Bloembergen, born in 1920, Dutch-American physicist and Nobel Prize winner. Bloembergen is noted for his pioneering research in laser spectroscopy, a technique that uses energy emissions to study the properties of matter. For his work in developing laser spectroscopy, Bloembergen received the 1981 Nobel Prize in physics, which he shared with Swedish physicist Kai Manne Borje Siegbahn and American physicist Arthur Leonard Schawlow.
Bloembergen was born in Dordrecht, the Netherlands, and received his Ph.D. degree in 1948 from the Leiden University. In 1951 he joined the faculty of Harvard University in Cambridge, Massachusetts, where he spent the remainder of his career. He became a United States citizen in 1958.
Spectroscopy is the study of the electromagnetic spectrum produced by a substance when exposed to certain kinds of energy, such as radiation. The substance absorbs or emits some of the energy, thereby producing a spectrum that can be carefully measured and analyzed. The spectrum provides information about molecular-energy levels, chemical bonds, and other features of the substance.
Bloembergen was especially interested in using lasers to excite a substance, and then studying the relative amounts of energy the substance absorbs. Lasers are intense beams of light waves. However, at very high intensities, the traditional laws of optics do not apply. Bloembergen worked out new laws of optics for these situations and used these laws to develop additional techniques for laser spectroscopy. Applications for these techniques range from the analysis of biological substances to the study of combustion in jet engines.
Swiss-born American physicist Felix Bloch won the Nobel Prize in physics in 1952. Bloch won the prize for his development of high-precision methods in nuclear magnetism and for discoveries stemming from these methods.
Felix Bloch (1905-1983), Swiss-born American physicist, educator, and cowinner of the 1952 Nobel Prize for physics. Bloch shared the Nobel Prize with American physicist Edward Mills Purcell for their development of a new method for the precise measurements of the strength of the magnetic field of the atomic nucleus, called nuclear magnetic resonance (NMR). A number of important applications have come from NMR, including magnetic resonance imaging (MRI). MRI produces detailed internal images of the human body, which helps physicians diagnose disease and injuries.
Born in Switzerland, Bloch studied engineering and physics at the Federal Institute of Technology in Zürich from 1924 to 1927. He received his Ph.D. degree in physics in 1928 from the University of Leipzig, Germany. From 1928 to 1932 he served as a researcher at a number of different universities in Europe and was a professor at the University of Leipzig from 1932 to 1933. Bloch left Germany in 1933 and worked at various institutions in Holland, Denmark, and Italy. He moved to the United States in 1934 after accepting an associate professorship of physics at Stanford University. He became an American citizen in 1939, and held his position at Stanford until his retirement in 1971. During World War II (1939-1945), Bloch worked on the Manhattan Project at Los Alamos (see Nuclear Weapons), contributing to the effort to develop an atomic bomb and to improve radar technology. In 1954 and 1955 he served as the first director-general of the European Organization for Nuclear Research (CERN), the multinational laboratory for nuclear science in Geneva, Switzerland.
In 1945 Bloch lead a team that successfully used a new method to measure the strength of the magnetic field of the nucleus using radio waves and nuclear magnetic resonance (NMR) to perform the measurements. In NMR, scientists can measure how much electromagnetic radiation of a specific frequency is absorbed by an atomic nucleus that is placed in a strong magnetic field (see Magnetism). This method helps to reveal atomic and molecular structures (see Atom). At the same time, Purcell and his research group at Harvard University made similar observations.
Scientists, researchers, and the general public continue to benefit from Bloch's discoveries. NMR revolutionized the field of chemistry and has become the most important spectroscopic (see Spectroscopy) technique in chemistry and biology. Scientists use NMR instruments to determine the moisture content of food, check the quality of drugs and medicines, and probe the nature of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) (see Nucleic Acids), the building blocks of human life.
American physicist Hans Albrecht Bethe won the Nobel Prize in physics in 1967. He studied thermonuclear fusion, the process by which hydrogen is converted into helium.
Hans Albrecht Bethe (1906-2005), German-born American physicist and Nobel laureate, noted for his contributions to theories of stellar energy production and to the development of nuclear weapons.
Hans Albrecht Bethe was born in Strasbourg, Alsace-Lorraine (then a part of Germany). He was educated at the University of Frankfurt and the University of Munich, from which he received a Ph.D. degree in 1928. Bethe taught physics at various universities in Germany from 1928 to 1933 and in England from 1933 until 1935, when he began his long association with Cornell University. He became a naturalized U.S. citizen in 1941.
Beginning in 1943 Bethe worked at Los Alamos, New Mexico, on the development of the atomic bomb, an effort known as the Manhattan Project. After initial misgivings he took part in the later development of the hydrogen bomb. At the same time Bethe continued his work for the peaceful use and international control of nuclear energy. A prime advocate of the partial test-ban agreement signed by the United States, the Soviet Union, and the United Kingdom in 1963, he later became an opponent of the Strategic Defense Initiative, proposed by the United States in the 1980s.
Bethe was awarded the 1967 Nobel Prize in physics for his studies of the production of energy by the Sun and other stars, which he postulated occurs through thermonuclear fusion, a long series of nuclear reactions by which hydrogen is converted into helium. He retired from Cornell in the mid-1970s but continued to be active in his field and to work for related causes into his 90s. See also Star (astronomy); Astrophysics.
American physicist John Bardeen won the Nobel Prize in physics in 1956 and again in 1972. The first prize was awarded for Bardeen’s part in developing the transistor, an electronic device that performed many of the functions of the vacuum tube. The second prize recognized his contribution to a theory that explains superconductivity—the total disappearance of electrical resistance in some materials at low temperatures.
John Bardeen (1908-1991), American physicist and Nobel laureate, born in Madison, Wisconsin, and educated at the University of Wisconsin and Princeton University. As a research physicist (1945-1951) at the Bell Telephone Laboratories in Murray Hill, New Jersey, he was a member of the team that developed the transistor, a tiny electronic device capable of performing most of the functions of the vacuum tube. For this work, he shared the 1956 Nobel Prize in physics with two colleagues, the American physicists William Shockley and Walter H. Brattain. Meanwhile he had joined (1951) the faculty of the University of Illinois. In 1972 he shared the Nobel Prize in physics with the American physicists Leon N. Cooper and John R. Schrieffer for the development of a theory to explain superconductivity, the disappearance of electrical resistance in certain metals and alloys at temperatures near absolute zero (see Cryogenics). Bardeen thus became the first scientist to win two Nobel Prizes in the same category.
John Vincent Atanasoff (1903-1995), American physicist, born in Hamilton, New York, who has been claimed as the developer of certain basic techniques later used in the design of the first electronic digital computer, ENIAC (Electronic Numerical Integrator and Computer). While teaching at Iowa State College, Atanasoff built a simple vacuum-tube computing device that he showed to several people, including one of the later builders of ENIAC, but he did not succeed in marketing his own device. A 1971 lawsuit by an electronics firm against a rival firm holding the patent on ENIAC principles, however—on the grounds that Atanasoff's ideas had been used without being credited—led to the invalidation of that patent in 1973.
Philip W. Anderson, born in 1923, American physicist and Nobel laureate who helped develop basic theories of magnetism and conduction in solid-state physics. Anderson shared the 1977 Nobel Prize for physics with British physicist Sir Nevill Francis Mott and American physicist John Hasbrouck Van Vleck.
Anderson was born in Indianapolis, Indiana. He earned his bachelor's, master's and doctoral degrees from Harvard University, where he was a student of John Van Vleck. Anderson studied at Harvard University from 1939 to 1949, except for the years 1943 to 1945, when he interrupted his education to work as a radio engineer in the United States Navy during World War II.
After he earned his doctorate from Harvard, Anderson went to work at Bell Laboratories in New Jersey. Anderson worked for Bell Laboratories until his retirement in 1984, while serving terms as professor of physics at several universities, including the University of Tokyo and Princeton University. From 1967 to 1975 Anderson was a visiting professor of theoretical physics at the University of Cambridge in England, where he worked with Nevill Mott.
Anderson's work focused on solid-state physics, also known as condensed-matter physics. One of the major advances of solid-state physics was the discovery of semiconductors in the 1920s. A semiconductor is a material that conducts electricity at room temperature more readily than an insulator, but less easily than a metal. Use of semiconductors made possible the development of integrated circuits, the components that control many electronic devices such as computers. One of the most important semiconductors is the crystalline form of silicon. Anderson's work concentrated on solids with no crystalline structure, which are called amorphous materials.
Anderson's work with amorphous materials like amorphous silicon led him to demonstrate in 1958 that it is possible for an electron to get trapped in a small area. This phenomenon, known as “Anderson localization,” suggests that amorphous materials can be used in place of the crystalline semiconductors used today. Anderson's discoveries also led to the development of electronic switching and memory devices made from amorphous materials such as glass. The field of amorphous semiconductors has become an area of intense research since Anderson's work.
American physicist Carl David Anderson won the Nobel Prize in physics in 1936. Anderson discovered the positron, a fundamental subatomic particle.
Carl David Anderson (1905-91), American physicist and Nobel laureate. Anderson was born in New York City and educated at the California Institute of Technology, where he attained full professorial rank in 1939. In 1932 he discovered the positron, or positive electron, one of the fundamental subatomic particles. For this achievement he was awarded, with Victor Franz Hess, the 1936 Nobel Prize in physics. In 1936 Anderson also confirmed experimentally the existence of the elementary nuclear particle called the meson, which had been predicted in 1935 by the Japanese physicist Yukawa Hideki.
Alexei Abrikosov, born in 1928, Russian-born American physicist and cowinner of the 2003 Nobel Prize in physics for theories that explained the properties of superconductors—metals and other substances that carry an electric current without any resistance when cooled to extremely low temperatures. Abrikosov’s insights during the 1950s helped propel an area of research that became very active in the 1980s and 1990s, as scientists developed new superconducting compounds. Superconductors are expected to find wide application in the future—for example, in new kinds of electric motors and generators, and in improved means for transmitting electric current long distances over power lines.
Abrikosov was born in Moscow in what was then the Union of Soviet Socialist Republics (USSR). He earned his doctoral degree in 1951 from the Institute for Physical Problems in Moscow, and another advanced degree, in quantum electrodynamics, from the same institution in 1955. After working at several institutions and universities in Russia, Abrikosov moved to the United States at the end of the Cold War in 1991, joining the staff at the Argonne National Laboratory outside Chicago, Illinois.
Research early in the 1900s had proved the existence of superconductivity in metals and other compounds that were cooled to near absolute zero, the lowest temperature possible: -273.15°C (-459.67°F). What was still lacking when Abrikosov began his research in the 1950s was a theoretical framework to explain how different superconducting systems worked, particularly in relation to magnetic fields. Two other Russian physicists, Vitaly L. Ginzburg and Lev Landau, explained the manner in which superconductors known at that time blocked or displaced magnetic fields. These superconductors were dubbed Type I. The theories of Ginzburg and Landau suggested another type of superconductor. Building on the Ginzburg-Landau theory, Abrikosov explained the phenomenon in which some superconductors admit a magnetic field and function in its presence under certain conditions. These superconductors were designated Type II.
Abrikosov’s theories accurately predicted the properties of Type II superconductors. These properties were subsequently discovered in new Type II superconducting compounds, including ceramic compounds that become superconducting at higher temperatures, which are more practical to achieve. Abrikosov’s theories on electricity and magnetic fields have also been applied in the development of magnetic resonance imaging (MRI) machines that can peer inside the human body, and in the high-energy accelerators that allow physicists to investigate fundamental subatomic particles, such as quarks.
In addition to the Nobel Prize, Abrikosov’s other distinctions include election to the Russian Academy of Sciences and the American Academy of Arts and Sciences. His Nobel Prize was shared with Ginzburg and with British-born American physicist Anthony J. Leggett, who was honored for separate work on the phenomenon of superfluidity.
Brian D. Josephson, born in 1940, Welsh physicist and one of the youngest recipients of a Nobel Prize. Josephson shared the 1973 Nobel for physics with Japanese physicist Leo Esaki and Norwegian-born American physicist Ivar Giaever for their research on tunneling effects in semiconductors and superconductors (see Superconductivity). According to classical physics, an electric current—and specifically, electrons—cannot flow in a circuit that is interrupted by an insulating barrier. Since the 1930s, many physicists had predicted that electrons might be able to “tunnel” through an insulating barrier if it was thin enough. Esaki, who first demonstrated tunneling in semiconductors, laid the groundwork for Giaever's research on superconducting tunnel junctions. Based on their discoveries, Josephson formulated theories predicting how electrons flow through a tunnel barrier.
Josephson was born in Cardiff, Wales. He attended Trinity College at the University of Cambridge, where he earned a B.A. (1960), an M.A. (1964), and a Ph.D. (1964) in physics. In 1962 he made his Nobel-prize winning observations about the behavior of an electrical contact between a superconducting material and a normal metal separated by a very thin insulating layer. Traditional quantum theory stated that only a small amount of current (electrons) could tunnel through the nonconducting barrier. Josephson predicted that a much higher number of electrons would actually move across the insulator. He also noted that this current would be affected by an external magnetic field. The flow of electric current through nonconductive material became known as the Josephson effect. Josephson's discoveries have had practical applications in the development of miniature electronics.
In 1964 Josephson took a teaching position at the University of Cambridge. He spent a year at the University of Illinois as a visiting research professor, returning to the University of Cambridge in 1967 to serve as assistant director of research in physics. He then worked as reader in physics for two years. In 1974 Josephson became professor of physics.
He shifted his research focus from physics to the scientific study of the mind after attending a 1971 lecture on transcendental meditation. He became interested in synthesizing modern physics and mathematics with the study of intelligence, language, higher states of consciousness, and the paranormal. With Indian chemical engineer V.S. Ramachandran, Josephson edited Consciousness and the Physical World (1979).
Egyptian American chemist Ahmed Zewail won the 1999 Nobel Prize in chemistry for his work in studying chemical reactions. Zewail
Ahmed H. Zewail, born in 1946, Egyptian American chemist and Nobel Prize winner. Zewail received the 1999 Nobel Prize in chemistry for developing a way to study chemical reactions in slow motion using ultra-short laser flashes. The Royal Swedish Academy of Sciences, which awards the Nobel Prize, said that his contributions have revolutionized chemistry, because this method of investigation enables chemists to understand and predict the nature of chemical reactions.
Zewail was born in Alexandria, Egypt. He received his bachelor's and master's degrees from the University of Alexandria. He moved to the United States and, in 1974, earned his Ph.D. degree from the University of Pennsylvania in Philadelphia. After completing his Ph.D., he went to the University of California at Berkeley as a research fellow. In 1976 Zewail joined the faculty at the California Institute of Technology (Caltech) in Pasadena, and in 1982 he became a full professor. In 1990 he became the first person to hold the Linus Pauling Chair of Chemical Physics at Caltech.
In a series of experiments he performed during the 1980s, Zewail developed what many have described as the world's fastest camera. This device uses flashes of laser light of such short duration that they “freeze” the moment when atoms and molecules come together to form new compounds. Using his laser technique, Zewail was the first person to find out how long it takes for atoms and molecules to form and to break chemical bonds. Using this ability, he has studied a variety of chemical processes, ranging from reactions in Earth’s atmosphere to biological reactions between genetic components within hemoglobin (a compound in red blood cells).
Zewail’s technique uses flashes of laser light that last for a few femtoseconds. One femtosecond equals one millionth of one billionth of a second (0.000000000000001 second). Femtochemisty is the area of physical chemistry that addresses the short time period in which chemical reactions take place and investigates why some reactions occur but not others. Zewail’s picture-taking technique made possible these investigations. One of the first major discoveries of femtochemistry was that intermediate products that form during chemical reactions differ from the starting and end products. By understanding these molecular dynamics, chemists one day may be able to better control chemical reactions and create new molecules.
Zewail has received numerous awards in addition to the Nobel Prize. In 1998 the government of Egypt issued a postage stamp bearing his portrait.
American scientist Luis Walter Alvarez won the 1968 Nobel Prize in physics. Alvarez developed the liquid hydrogen bubble-chamber, which he used to find atomic particles.
Luis Alvarez (1911-1988), American scientist. Luis Walter Alvarez was born in San Francisco and educated at the University of Chicago. He won the 1968 Nobel Prize in physics for developing the liquid hydrogen bubble-chamber, with which he found atomic particles produced by high-energy nuclear events. He also developed the proton linear accelerator known as LINEAC. Alvarez had wide-ranging interests in science. In 1981 he and his son Walter, after studying geological strata, published a controversial theory that a giant meteorite striking the earth had caused the extinction of the dinosaurs (see Dinosaur; Evolution).
American physicist William Philips shared the 1997 Nobel Prize in physics with two other reasearchers. Philips was recognized for his work on ways to cool and trap atoms.
William D. Philips, born in 1948, American physicist and Nobel laureate. Philips’s advancements in the use of special beams of light called lasers to slow, cool, and capture atoms (tiny particles that make up matter) were instrumental in furthering the study and use of atoms. In the late 1980s Philips used laser cooling to cool and slow atoms to a point not thought possible at the time. He shared the 1997 Nobel Prize for physics with two other scientists who made separate but complementary advancements, Steven Chu of the United States and Claude Cohen-Tannoudji of France. Their achievements led to a breakthrough in the study and manipulation of atoms, which in turn brought improvements to many applications, including global navigation and gravitational measurement techniques.
Philips was born in Wilkes-Barre, Pennsylvania. He earned a B.S. degree in physics at Juniata College in Huntingdon, Pennsylvania, in 1970. In 1976 he earned his Ph.D. degree in physics from Massachusetts Institute of Technology (MIT). After post-doctoral research at MIT, in 1978 he joined the National Institute of Standards and Technology (NIST), then known as the National Bureau of Standards.
Hired to work with precision electrical measurements, Philips soon also began conducting experiments in trapping atoms. He made advancements using a magnetic device to slow atoms. Meanwhile Steven Chu and a team at Bell Laboratories in Holmdel, New Jersey, began furthering the use of lasers to capture atoms. In 1985 Chu successfully used lasers in a vacuum chamber to cool atoms to 240 millionths of a Celsius degree (430 millionths of a Fahrenheit degree) above absolute zero, the point at which all matter stops moving (–273.15° C, or -459.67° F).
Philips adopted Chu’s techniques, and by 1988 Philips and his research team had cooled atoms to 40 millionths of a Celsius degree (70 millionths of a Fahrenheit degree) above absolute zero, lower than scientists thought was theoretically possible at the time. Philips came up with methods to capture atoms at regular intervals in what was termed an optical lattice.
At room temperature, atoms move at speeds of about 4000 km/h (2500 mph), much too fast for scientists to study them. The rate at which atoms move is related to the temperature of the matter made up by the atoms. Lowering the temperature of the sample of atoms slows the atoms’ motion, and vice versa. Chu and Philips developed techniques in which atoms are bombarded with finely tuned laser beams. The lasers immerse the atoms in packets of light wave energy called photons. The photons strike the atoms in a way that is roughly like raindrops hitting a beach ball. The photons have no mass, but because they travel at the speed of light, they carry enough momentum to hit the atoms and slow them down. By 1995 Claude Cohen-Tannoudji and his team used similar techniques to lower the temperature of a sample of atoms to 0.2 millionths of a Celsius degree (0.4 millionths of a Fahrenheit degree) above absolute zero.
The ability to manipulate atoms and study them more closely led to many immediate and many potential applications. Trapped atoms have increased the accuracy of atomic clocks, which increases the accuracy of other instruments that use atomic clocks, such as navigation systems. Control of atoms also helps calibrate instruments used to measure the force of gravity at spots on the earth. These measurements indicate different densities within the earth, which can reveal features such as petroleum deposits beneath the earth’s surface. The ability to manipulate atoms also raises the possibility of using atoms to etch electronic circuits, thereby increasing the circuits’ capabilities by increasing the number of circuits that can fit in a certain area.
In the 1990s Philips continued his research into ultra-cold trapped atoms. In 1995 he was elected to the American Academy of Arts and Sciences and became an NIST Fellow. Two years later he was named to the National Academy of Sciences.
Pakistani physicist Abdus Salam won the 1979 Nobel Prize in physics. He won the award for his work in developing a unification hypothesis concerning electromagnetic and weak interactions between atomic particles.
Abdus Salam (1926-1996), Pakistani physicist and Nobel laureate, known for his contributions to the understanding of the interactions of elementary particles. Salam was born in Jhang Sadar, India (now in Pakistan), attended the Government College at Lahore, and received a doctorate in mathematics and physics from the University of Cambridge in 1952. He taught at both institutions before becoming professor of theoretical physics at Imperial College, London, in 1957, and he was made director of the International Centre for Theoretical Physics in Trieste, Italy, when it was established in 1964. In 1967, with the American physicist Steven Weinberg, Salam offered a so-called unification hypothesis that incorporated the known facts about the electromagnetic and weak interactions between atomic particles (Elementary Particles). When tested, the hypothesis held up, unlike a number of alternative hypotheses. The men shared the 1979 Nobel Prize in physics for this work with American physicist Sheldon Lee Glashow, who also contributed to the understanding of particle interactions.
Askar Akayev was elected president of Kyrgyzstan in the country’s first presidential elections in 1991. He won a third term in 2000, but mass protests in 2005 forced him to flee the country and resign.
Askar A. Akayev, born in 1944, president of Kyrgyzstan from 1991 to 2005. Askar Akayevich Akayev was born in the town of Kyzyl-Bayrak in Kyrgyzstan, which was then the Kirgiz Soviet Socialist Republic (SSR) within the Union of Soviet Socialist Republics (USSR). He was educated as a physicist and spent 20 years in Leningrad (now Saint Petersburg, Russia), where he graduated with honors from the Institute of Precision Engineering and Optics. Akayev joined the Communist Party in 1981, and in 1984 he became a corresponding member of the USSR Academy of Sciences. He was selected to the vice presidency of the Kirgiz SSR Academy of Sciences in 1987, and he became the academy’s president in 1989. In 1991 he became a member of the USSR Supreme Soviet Committee on Economic Reform.
During a wave of liberalizing political reforms initiated by the leader of the USSR, Mikhail Gorbachev, Akayev was indirectly elected to the Kirgiz SSR’s newly created post of president in 1990. The republic’s parliament elected him largely because he was a liberal academic who had worked only briefly in the Communist Party apparatus. When Communist hardliners attempted a coup against Gorbachev in August 1991, Akayev was the first leader of a Soviet republic to denounce their plot. He also severed his ties to the Communist Party. After the failed coup attempt, Kyrgyzstan and other Soviet republics began to declare their independence. In October the people of Kyrgyzstan elected Akayev as president in the country’s first direct presidential elections. The USSR officially ceased to exist in December, and Kyrgyzstan joined most of the former Soviet republics in forming a loose alliance called the Commonwealth of Independent States (CIS).
Akayev immediately began to promote market-oriented reforms to restructure Kyrgyzstan’s Soviet-developed economy. Through his influence, in 1993 Kyrgyzstan became the first former Soviet republic in Central Asia to introduce its own currency, the som. Akayev also worked to establish diplomatic and economic ties with countries outside the former USSR, including the United States and other Western nations. In addition, Akayev joined Kyrgyzstan in economic and security alliances with other members of the CIS, as well as China. Akayev’s commitment to rapid economic reform helped Kyrgyzstan secure international financial assistance, including funds for infrastructure development projects.
Akayev also advocated democratic reforms, in contrast to the leaders of the other newly independent nations in Central Asia. As opposition parties and a free press became established, however, Akayev faced public criticism of his policies, as well as political opposition within the parliament. Kyrgyzstan’s new constitution, adopted in 1993, created a parliamentary system of government that transferred the functions of the head of government from the president to the prime minister. However, voters strongly endorsed Akayev and his economic programs in a 1994 referendum, strengthening his political position.
Akayev was reelected president in December 1995. Emboldened by his victory, he called for a referendum in February 1996 on constitutional amendments to enhance the powers of the president at the expense of the parliament. He claimed the changes were necessary to permit further economic restructuring in Kyrgyzstan. The referendum passed by an overwhelming majority.
In the following years, Akayev’s commitment to democratic reform was called into question. He appeared to become less tolerant of political opposition. Politicians and newspapers critical of his policies were subject to imprisonment or closure. Akayev remained committed to economic reform, but he was widely blamed for increasing poverty and lack of adequate social services.
Despite the constitutional limit of two presidential terms, the Constitutional Court of Kyrgyzstan ruled in 1998 that Akayev’s first term, which began under the old constitution, should not be counted. In 2000 Akayev was reelected with 74.5 percent of the vote in an election marred by voting irregularities. In February 2005 protests erupted in the country after some opposition candidates were disqualified from running in legislative elections. In March protestors stormed government buildings in Bishkek, and Akayev fled the country. He formally resigned in early April.
