Prado.Petkevich.Spring2010.AtomicTimeline

=__**Atomic Timeline:**__ =

Democritus


-460-370 BCE Country of Origin: Greece Bio: His father contributed largely towards the entertainment of the army of Xerxes upon his return to Asia. As a reward for this the Persian monarch gave him several Magi. Democritus was instructed by these Magi in astronomy and theology. He is said to have visited Egypt, Ethiopia, Persia, and India. During some part of his life he was instructed in Pythagoreanism. He was acquainted with the virtues of herbs, plants, and stones, and spent his life in making experiments upon natural bodies. He acquired fame with his knowledge of natural phenomena, and predicted changes in the weather. He used this ability to make people believe that he could predict future events. Democritus has been commonly known as “The Laughing Philosopher,” and he never appeared in public without expressing his contempt of human follies while laughing. He died at more than a hundred years of age.

Year/Description of Discovery: Democritus expanded the atomic theory of Leucippus. He maintained the impossibility of dividing things //ad infinitum//. From the difficulty of assigning a beginning of time, he argued the eternity of existing nature, of void space, and of motion. He supposed the atoms, which are originally similar, to be impenetrable and have a density proportionate to their volume.

1700-1800
 -September 6, 1766 to July 27, 1884
 * John Dalton**

1875-1900
-March 27, 1845 to February 10, 1923 Country of Origin: Germany Bio: When Wilhelm Conrad Röntgen was three years old, his family moved to Apeldoorn in The Netherlands, where he went to the Institute of Martinus Herman van Doorn, a boarding school. In 1862 he entered a technical school at Utrecht, where he was expelled. He then entered the University of Utrecht in 1865 to study physics. Not having attained the credentials required for a regular student, and hearing that he could enter the Polytechnic at Zurich by passing its examination, he passed this and began studies there as a student of mechanical engineering. In 1869 he graduated Ph.D. at the University of Zurich. In 1874 he qualified as Lecturer at Strasbourg University and in 1875 he was appointed Professor in the Academy of Agriculture at Hohenheim in Württemberg. In 1876 he returned to Strasbourg as Professor of Physics, but three years later he accepted the invitation to the Chair of Physics in the University of Giessen. In 1899 he declined an offer to the Chair of Physics in the University of Leipzig, but in 1900 he accepted it in the University of Munich, by special request of the Bavarian government, as successor of E. Lommel. Here he remained for the rest of his life.
 * Wilhelm C. Röntgen**

Year/Description of Discovery: On the evening of November 8, 1895, he found that, if the discharge tube is enclosed in a sealed, thick black carton to exclude all light, and if he worked in a dark room, a paper plate covered on one side with barium platinocyanide placed in the path of the rays became fluorescent even when it was as far as two metres from the discharge tube. During subsequent experiments he found that objects of different thicknesses interposed in the path of the rays showed variable transparency to them when recorded on a photographic plate. When he immobilised for some moments the hand of his wife in the path of the rays over a photographic plate, he observed after development of the plate an image of his wife's hand which showed the shadows thrown by the bones of her hand and that of a ring she was wearing, surrounded by the penumbra of the flesh, which was more permeable to the rays and therefore threw a fainter shadow. This was the first "röntgenogram" ever taken. In further experiments, Röntgen showed that the new rays are produced by the impact of cathode rays on a material object. Because their nature was then unknown, he gave them the name X-rays.

-December 15, 1852 to August 25, 1908 Country of Origin: France Bio: Antoine Henri Becquerel entered the Polytechnic in 1872, then the government department of Ponts-et-Chaussées in 1874, becoming ingénieur in 1877 and being promoted to ingénieur-en-chef in 1894. In 1888 he acquired the degree of docteur-ès-sciences. In 1892 he was appointed Professor of Applied Physics in the Department of Natural History at the Paris Museum. He became a Professor at the Polytechnic in 1895. Becquerel published his findings in many papers, principally in the Annales de Physique et de Chimie and the Comptes Rendus de l'Academie des Sciences. He was elected a member of the Academie des Sciences de France in 1889 and succeeded Berthelot as Life Secretary there. He was a member also of the Accademia dei Lincei and of the Royal Academy of Berlin, amongst others. He was made an Officer of the Legion of Honour in 1900.
 * Henri Becquerel**

Year/Description of Discovery: In 1896, Becquerel made his discovery of the phenomenon of natural radioactivity. Following a discussion with Henri Poincaré on the radiation which had recently been discovered by Röntgen (X-rays) and which was accompanied by a type of phosphorescence in the vacuum tube, Becquerel decided to investigate whether there was any connection between X-rays and naturally occurring phosphorescence. He had inherited from his father a supply of uranium salts, which phosphoresce on exposure to light. When the salts were placed near to a photographic plate covered with opaque paper, the plate was discovered to be fogged. The phenomenon was found to be common to all the uranium salts studied and was concluded to be a property of the uranium atom. Later, Becquerel showed that the rays emitted by uranium, which for a long time were named after their discoverer, caused gases to ionize and that they differed from X-rays in that they could be deflected by electric or magnetic fields. For his discovery of spontaneous radioactivity Becquerel was awarded half of the Nobel Prize for Physics in 1903, the other half being given to Pierre and Marie Curie for their study of the Becquerel radiation.

-December 18, 1856 to August 30, 1940
 * J.J. Thomson**

-November 7, 1867 to July 4, 1934

1900-1915
-March 22, 1868 to December 19, 1953 Country of Origin: U.S.A. Bio: Robert Andrews Millikan led a rural existence in childhood, attending the Maquoketa High School (Iowa). After working for a short time as a court reporter, he entered Oberlin College in 1886. After his graduation in 1891 he took, for two years, a teaching post in elementary physics. In 1893, after obtaining his mastership in physics, he was appointed Fellow in Physics at Columbia University. He afterwards received his Ph.D. (1895) for research on the polarization of light emitted by incandescent surfaces. He spent a year (1895-1896) in Germany, at the Universities of Berlin and Göttingen. Throughout his life Millikan remained an author, making numerous contributions to scientific journals. He was President of the American Physical Society, Vice-President of the American Association for the Advancement of Science, and was the American member of the Committee on Intellectual Cooperation of the League of Nations, and the American representative at the International Congress of Physics, known as the Solvay Congress, at Brussels in 1921. He held honorary doctor's degrees of some twenty-five universities, and was a member or honorary member of many learned institutions in his country and abroad.
 * Robert Millikan**

Year/Description of Discovery: Millikan made numerous momentous discoveries, chiefly in the fields of electricity, optics, and molecular physics. His earliest major success was the accurate determination of the charge carried by an electron, using the "falling-drop method"; he also proved that this quantity was a constant for all electrons (1910), thus demonstrating the atomic structure of electricity. Next, he verified experimentally Einstein's all-important photoelectric equation, and made the first direct photoelectric determination of Planck's constant h (1912-1915). In addition his studies of the Brownian movements in gases put an end to all opposition to the atomic and kinetic theories of matter. During 1920-1923, Millikan occupied himself with work concerning the hot-spark spectroscopy of the elements (which explored the region of the spectrum between the ultraviolet and X-radiation), thereby extending the ultraviolet spectrum downwards far beyond the then known limit. The discovery of his law of motion of a particle falling towards the earth after entering the earth's atmosphere, together with his other investigations on electrical phenomena, ultimately led him to his significant studies of cosmic radiation (particularly with ionization chambers).

-August 30, 1871 to October 19, 1937 Country of Origin: New Zealand Bio: Ernest Rutherford received his early education in government schools and at the age of 16 entered Nelson Collegiate School. In 1889 he was awarded a University scholarship and he proceeded to the University of New Zealand, Wellington, where he entered Canterbury College. He graduated M.A. in 1893 with a double first in Mathematics and Physical Science and he continued with research work at the College for a short time, receiving the B.S. degree the following year. That same year, 1894, he was awarded an 1851 Exhibition Science Scholarship, enabling him to go to Trinity College, Cambridge, as a research student at the Cavendish Laboratory under J.J. Thomson. In 1897 he was awarded the B.A. Research Degree and the Coutts-Trotter Studentship of Trinity College. An opportunity came when the Macdonald Chair of Physics at McGill University, Montreal, became vacant, and in 1898 he left for Canada to take up the post. Rutherford was knighted in 1914; he was appointed to the Order of Merit in 1925, and in 1931 he was created First Baron Rutherford of Nelson, New Zealand, and Cambridge. He was elected Fellow of the Royal Society in 1903 and was its President from 1925 to 1930. Amongst his many honors, he was awarded various medals and honorary doctorates too numerous to list.
 * Ernest Rutherford**

Year/Description of Discovery: In 1910, Rutherford’s investigations into the scattering of alpha rays and the nature of the inner structure of the atom which caused such scattering led to the postulation of his concept of the "nucleus", his greatest contribution to physics. According to him practically the whole mass of the atom and at the same time all positive charge of the atom is concentrated in a minute space at the centre. In 1913, together with H. G. Moseley, he used cathode rays to bombard atoms of various elements and showed that the inner structures correspond with a group of lines which characterize the elements. Each element could then be assigned an atomic number and, more important, the properties of each element could be defined by this number. In 1919 he discovered that the nuclei of certain light elements, such as nitrogen, could be "disintegrated" by the impact of energetic alpha particles coming from some radioactive source, and that during this process fast protons were emitted. Rutherford was the first to deliberately transmute one element into another.

-October 7, 1885 to to November 18, 1962
 * Niels Bohr**

1915-1950

 * Erwin Schrodinger**

-August 12, 1887 to January 4, 1961

-December 5, 1901 to February 1, 1976 Country of Origin: Germany Bio: It was his father's commitment to academic learning that led Werner Heisenberg to pursue the science he loved. He graduated from the University of Munich, where his father was professor of Greek language and literature. He taught himself calculus and tried to publish a scientific paper as a teen. Even though his strongest interest in life was science, music was a lifetime companion for him. A hard worker, Heisenberg worked on a farm for three summers in order to pay for his tuition to the University of Munich. After more hard work he received his doctorate in Munich in 1923. From there Heisenberg went to the Niels Bohr Institute in Copenhagen, Denmark, where he eagerly studied the most creative and up-to-date thoughts on atomic theory. When World War II began, the government appointed him as director of the German uranium project, and he worked on developing an atomic bomb for Germany. Heisenberg was arrested and placed in captivity in England from April 1945 until the summer of 1946. In 1955 and 1956 Heisenberg wrote and published //Physics and Philosophy: The Revolution in Modern Science.// Heisenberg retired in 1970. His health began to fail in 1973, and shortly thereafter he became seriously ill, dying on February 1, 1976, in Munich, Germany.
 * Werner Heisenberg**

Year/Description of Discovery: Heisenberg worked out a complete method of calculating the energy levels of "atomic oscillators" (devices for producing alternating current). The method brought about very good results. In 1926 he was appointed lecturer in theoretical physics at the University of Copenhagen. It was at Copenhagen that Heisenberg formulated the famous uncertainty principle, which states that it is impossible to specify the exact position and momentum of a particle at the same time. In 1927, at the age of twenty-six, he became professor of theoretical physics at the University of Leipzig. He received the Nobel Prize for physics in 1932.

-October 20, 1891 to July 24, 1974
 * James Chadwick**

Sources:
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