The Curie's
Pierre and Marie Curie are best known for their pioneering work in the study of RADIOACTIVITY, which led to their discovery in 1898 of the elements RADIUM and POLONIUM. Marie Curie spent many years as a governess and teacher before studying mathematics and physics at the Sorbonne in Paris, earning degrees in both subjects in 1893 and 1894.

Albert Einstein
The German-American physicist Albert Einstein contributed more than any other scientist to the 20th-century vision of physical reality. In the wake of World War I, Einstein's theories--especially his theory of RELATIVITY--seemed to many people to point to a "pure quality of human thought," one far removed from the war and its aftermath. (Source: Grolier Electronic Publishing, Inc., 1995)

Werner Karl Heisenberg
German theoretical physicist Werner Karl Heisenberg 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 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 linear momentum--can be determined simultaneously. (Source: Grolier Electronic Publishing, Inc., 1995)

Volta
The Italian physicist Alessandro Giuseppe Antonio Anastasio Volta, was the inventor of the voltaic pile, the first electric battery. In 1775 he invented the electrophorus, a device that, once electrically charged by having been rubbed, could transfer charge to other objects. Between 1776 and 1778, Volta discovered and isolated methane gas. When Luigi Galvani's experiments with "animal electricity" were published in 1791, Volta began experiments that led him to theorize that animal tissue was not necessary for conduction of electricity. Proof of this theory was the battery, which Volta invented in 1800. Volta taught at Como Gymnasium (1775-78) and at Pavia University (1778-1815). Napoleon made him a count in 1801. The unit of electric potential, the volt, is named in his honor. (Source: Grolier Electronic Publishing, Inc., 1995)

Archimedes
In theoretical mechanics, Archimedes is responsible for fundamental theorems concerning the centers of gravity of plane figures and solids, and he is famous for his theorem on the weight of a body immersed in a liquid, called ARCHIMEDES' PRINCIPLE. A famous story, unfortunately with no foundation, relates that having discovered this while in the bath, he ran naked through the streets crying, "Eureka," or "I have found it." Archimedes' treatises are remarkable for their original ideas, rigorous demonstrations, and excellent computational technique. (Source: Grolier Electronic Publishing, Inc., 1995)

Andre Ampere
Andre Ampere was a French physicist who laid the foundations for the science of electrodynamics through his demonstration that electric currents produce magnetic fields. "Current" is like water flowing in a river. Current is expressed in units called Amps, which were named for Andre Ampere. An Amp equals 6.28x1018 electrons per second. and through his subsequent investigation into the relationship between these two phenomena. Ampere's most notable achievements were his independent determination of Avogadro's law and his work from 1820 to 1827 based on OERSTED'S discovery that a magnetic needle moves in the vicinity of an electric current. Ampere succeeded in explaining the latter phenomenon by assuming that an electric current is capable of exciting a magnetic field. He further demonstrated that the direction of the magnetic field is determined by the direction of the current. Ampere may be best known for producing a definition of the unit of measurement of current flow, now known as the AMPERE. (Source: Grolier Electronic Publishing, Inc., 1995)

Georg Simon Ohm
The German physicist Georg Simon Ohm, for whom the unit of electrical resistance, the ohm, was named, determined (1826) Ohm's law--the relationship between the flow of current, the voltage, and the resistance in a closed circuit (see ELECTRICITY). Ohm's scientific contemporaries were slow to recognize his achievement, failing to realize how closely his conclusions were derived from careful experimental work and especially how his discovery ordered vast quantities of existing experimental data. For most of his life Ohm held only poorly paid teaching jobs, but in 1852 he was given the chair of physics at the University of Munich based on his scientific accomplishments. (Source: Grolier Electronic Publishing, Inc., 1995)

Robert Boyle
The English natural philosopher and chemist Robert Boyle made important contributions to experimental chemistry and is known for his ideal GAS LAW, subsequently termed Boyle's Law. Boyle became interested in medicine and the new science of Galileo and studied chemistry. Boyle's earliest publication was on the physical properties of air, from which he derived his law that the volume of a given amount of a gas varies inversely with pressure. Boyle was a skillful experimenter who insisted that experimentation was an essential part of scientific proof, an approach that influenced Sir Isaac NEWTON and the methodology of many later scientists. (Source: Grolier Electronic Publishing, Inc., 1995)

Thomas Edison
Thomas Alva Edison was one of the most prolific inventors of the late 19th century. He is most famous for his development of the first commercially practical incandescent lamp (1879). Perhaps his greatest contribution, however, was the development (1882) of the world's first central electric light-power station (see POWER, GENERATION AND TRANSMISSION OF). His early laboratories were forerunners of the modern industrial research laboratory, where skilled researchers jointly solve technological problems. (Source: Grolier Electronic Publishing, Inc., 1995)

James Watt
James Watt was a Scottish engineer and inventor who played an important part in the development of the STEAM ENGINE as a practical power source. He studied instrument making and in 1755 went to London (at the age of 18) to study further and practice his trade. The unit of power is called the Watt, named after James Watt, who also happened to invent the first practical steam engine design. The Watt symbol is W, and it is equal to 1/746 of a horsepower, or one Volt times one Amp. Although Watt did not invent the steam engine itself, his improved engine was really the first useful device for efficiently converting heat into useful work and was a key stimulus to the Industrial Revolution. (Source: Grolier Electronic Publishing, Inc., 1995)

George Stephenson
George Stephenson, extremely poor as a young man, worked in local collieries and taught himself to read and write in his spare time. In 1812, he became a colliery engine builder, and in 1814 he built his first locomotive. When the Stockton and Darlington Railway was projected, George Stephenson was retained as company engineer. He convinced the owners to use steam motive power and built the line's first locomotive, the Locomotion. In 1825, Stephenson moved to the Liverpool and Manchester Railway. He and his son Robert built (1826-29) the Rocket, which won the competition held to design a suitable steam locomotive for that railroad. (Source: Grolier Electronic Publishing, Inc., 1995)

The Wright Brothers
The Wright brothers' interest in aviation started in 1896, when they learned of early European experiments in sustained FLIGHT. They began a program for building an airplane by first conducting tests with kites and then gliders. Before attempting powered flight, they solved the essential problems of controlling a plane's motion in rising, descending, and turning. An isolated beach near Kitty Hawk, N.C., was selected for flight tests on the advice of the U.S. Weather Bureau. After making more than 700 successful glider flights at Kitty Hawk in 1902, the Wright brothers faced the problem of finding an engine light enough and powerful enough to get their plane off the ground. No automobile manufacturer would accept the assignment, so the Wright brothers, along with Charles Taylor, designed and built their own 12-to-16 horsepower engine and propeller for their plane, which was originally named Flyer I, and commonly called Kitty Hawk. On Dec. 17, 1903, Orville achieved the first successful flight ever made in a self-propelled heavier-than-air craft. In 1907, the Wright brothers contracted with the U.S. Army Signal Corps to build a plane capable of carrying two men on flights of up to 200 km (125 mi). The plane was delivered and tests were completed in June 1909. Their first commercial success was with a French syndicate in 1908; in 1909, the American Wright Company was formed. (Source: Grolier Electronic Publishing, Inc., 1995)

Dr. Jekyll and Mr. Hyde
The idea for The Strange Case of Dr. Jekyll and Mr. Hyde (1886) came to its author, Robert Louis STEVENSON, in a dream. In the story, a respectable physician, Dr. Jekyll, can chemically transform himself into a monster, Mr. Hyde, who reflects the worst side of Dr. Jekyll's personality. Jekyll is fatally attracted to becoming Mr. Hyde, and Mr. Hyde takes over completely. The personality division suggests Sigmund FREUD'S duality of id and superego and the inevitable conflict between them. There are many movies available based on this work. (Source: Grolier Electronic Publishing, Inc., 1995)

Isaac Newton
Newton's greatest achievement was his work in physics and CELESTIAL MECHANICS, which culminated in the theory of universal GRAVITATION. It is not true that he discovered universal gravitation in 1666 while watching an apple fall from a tree in his garden. That story is simply a myth. By 1666, Newton had formulated early versions of his three LAWS OF MOTION. He had also discovered the law stating the centrifugal force (or force away from the center) of a body moving uniformly in a circular path. (Source: Grolier Electronic Publishing, Inc., 1995)

Samuel Morse
Samuel Finley Breese Morse achieved distinction both as an artist, particularly as a painter of miniatures, and as an inventor. Morse was educated at Yale College but also went to Europe for art training. It was during the return voyage from one such trip (1832) that he conceived of an electromagnetic signaling system. Although Morse continued with his artistic activities in New York and became first president of the National Academy of Design, his main activity after 1837 was the development of an electric TELEGRAPH. Morse's important contribution was that he based his receiver on the ELECTROMAGNET. This feature ultimately ensured the universal adoption of his system. When the electromagnet was energized by a pulse of current from the sender, a soft iron armature was attracted to the magnet and it produced marks, or variations, in a straight line that was being recorded on a moving strip of paper. The grouping of such marks symbolized the words of a message. Morse soon devised a code whereby letters and numbers were represented by combinations of dot and dash symbols, which corresponded to signals of short and long duration. With the aid of Alfred Vail, the original receiver was greatly improved and adapted to print the dot-and-dash symbols. Such a system was used in the first U.S. telegraph link that Morse set up in 1844 between Baltimore and Washington. (Source: Grolier Electronic Publishing, Inc., 1995)