Fall.2008.MMA.Esposito.Timeline

Democritus agreed that everything which is must be eternal, but denied that "the void" can be equated with nothing. This makes him the first thinker on record to argue the existence of an entirely empty "void". In order to explain the change around us from basic, unchangeable substance he created a theory that argued that there are various basic elements which always existed but can be rearranged into many different forms. Democritus' theory argued that atoms only had several properties, particularly size, shape, and (perhaps) weight; all other properties that we attribute to matter, such as color and taste, are but the result of complex interactions between the atoms in our bodies and the atoms of the matter that we are examining. "Sweet exists by convention, bitter by convention, color by convention; but in reality atoms and the void alone exist." http://www.perseus.tufts.edu/GreekScience/Students/Marc/short_paper.html
 * Democr**[[image:Democritus.jpg width="98" height="131" align="left"]]**itus 460 BC- 370 BC**
 * http://en.wikipedia.org/wiki/Democritus

Aristotle 384 BC – 322 BC** Together with Plato and Socrates (Plato's teacher), Aristotle is one of the most important founding figures in Western philosophy. He was the first to create a comprehensive system of Western philosophy, encompassing morality and aesthetics, logic and science, politics and metaphysics. Aristotle further explains that in each element one po wer is dominant. Therefore Earth is predominantly dry; water predominantly cool, air predominantly moist, and fire predominantly warm. The dominant power is the one in a counterclockwise direction from the element in the Square of Opposition; thus the arrow by each element points to its dominant power. The vertical axis represents the active qualities (warm and cool), the horizontal represents the passive (moist and dry). The upper Elements (air and fire) are active, light and ascending, the lower (water and earth) are passive, heavy and descending. The Elements on the right are pure, extreme and absolutely light (fire) or heavy (Earth); those on the left are mixed, intermediate and relatively light (air) or heavy (water). The absolute elements exhibit unidirectional motion (ascending Fire, descending Earth), whereas the relative Elements (Air, Water) can also expand horizontally. http://en.wikipedia.org/wiki/Aristotle
 * http://www.ucmp.berkeley.edu/history/aristotle.html

John Dalton 1766-1844** During Dalton's time Democritus' theory of the atom was not widely accepted. Dalton swayed people's opinion about atomic structure with his five main theories about atoms. His first theory was that elements are made of tiny particles called atoms. His second theory stated all the atoms of a given element are identical. Another of his theories stated atoms of one element are different from those of another element, and that different elements can distinguished by their given weights. Dalton's fourth theory of atoms was two different elements' atoms can combine to form chemical compounds, and that a given compound always has the same number of types of atoms. Dalton's fifth and final theory stated that atoms cannot be created, made smaller, destroyed by chemical means; the chemical process only changes the grouping of atoms. http://en.wikipedia.org/wiki/John_Dalton http://www.chemheritage.org/classroom/chemach/periodic/dalton.html

In 1861, Crookes discovered a previously unknown element with a bright green emission line in its spectrum and named the element thallium, from the Greek //thallos//, a green shoot. Crookes also identified the first known sample of helium, in 1895. He was the inventor of the Crookes radiometer, which today is made and sold as a novelty item. He also developed the Crookes tubes, investigating canal rays. From 1850 to 1854 he filled the positio n of assistant in the college, and soon embarked upon original work, not in organic chemistry  whe  re the inspiration of his distinguished teacher, August Wilhelm von Hofmann, might have been expected to lead him, but on certain new compounds of the element selenium. These formed the subject of his first published papers in 1851. the metho d of spectral analysis, introduced by Bunsen and Kirchhoff , was received by Crookes with great enthusiasm and to great effect. His first important discovery was that of the element thallium, announced in 1861, and made with the help of spectroscopy. By this work his reputation became firmly established, and he was elected a fellow of the //Royal Society// in 1863. Crookes' attention had been attracted to the vacu um bala nce in the course of the thallium researches. He soon discovered the phenomenon upon which depends the action of the well-known little instrument, the Crookes radiometer, in which a system of vanes, each blackened on one side and polished on the other, is set in rotation when exposed to radiant energy.
 * William Crookes 1832-1919**

http://people.clarityconnect.com/webpages2/arcsandsparks/mineraltube.html
 * http://en.wikipedia.org/wiki/William_Crookes

J.J. Thompson 1856-1940** Joseph J. Thomson was born in 1856 in Cheetham Hill, Manchester in England, of Scottish parentage. In 1870 he studied engineering at University of Manchester known as Owens College at that time, and moved on to Trinity College, Cambridge in 1876. In 1880, he obtained his BA in mathematics ( Second Wrangler and 2nd Smith's prize ) and MA (with Adams Prize ) in 1883. In 1884 he became Cavendish Professor of Physics. One of his students was Ernest Rutherford, who would later succeed him in the post. In 1890 he married Rose Elisabeth Paget, daughter of Sir George Edward Paget, KCB, a physician and then Regius Professor of Physic at Cambridge. He was awarded a Nobel Prize in 1906, "in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases." He was knighted in 1908 and appointed to the Order of Merit in 1912. In 1914 he gave the Romanes Lecture in Oxford on "The atomic theory". JJ Thompson was most known for his experiments with rays. Thompson took cathode rays and cathode ray tubes, which lead to the dicovery of electrons and subatomic paritcles. In his first experiment he wanted to se e if he could remove the negative charge by means of magnatism. he found that the rays would bend but the negative charge was inseperable. In his second experiemnt he tried to bend rays with an electrical charge.This time he used a cathode ray tube with an almost perfect vacuum. He discoverd that the rays did bend towrds the negative charge. In his final experiment he wnated to measure the mass to charge ratio. He did this by how much they deflected and the amount of energy they had. What he concluded was that atoms are actually divisible. Thompson used his experiments with rays to come up with the Plum Pudding model of atomic structure. In this model, the atom is composed of electrons surrounded by a soup of positive charge to balance the electron's negative charge, like negatively-charged "plums" surrounded by positively-charged "pudding". http://www.aip.org/history/electron/jjhome.htm http://en.wikipedia.org/wiki/JJ_Thompson http://www.visionlearning.com/library/module_viewer.php?mid=50

Röntgen was born at Lennep in Rhenish Prussia as the only child of a merchant and manufacturer of cloth. In March 1848, the family moved to Apeldoorn and Wilhelm was raised in the Netherlands. He received his early education at the Institute of Martinus Herman van Doorn, a private school in Apeldoorn. From 1861 to 1863, he attended the Utrecht Technical School. In 1869, he graduated with a Ph.D. from the University of Zurich. During 1895 Röntgen was investigating the external effects from the various types of vacuum tube equipment—apparatus from Heinrich Hertz, Johann Hittorf , William Crookes , Nikola Tesla and Philipp von Lenard —when an electrical discharge is passed through them. In early November he was repeating an experiment with one of Lenard's tubes in which a thin aluminium window had been added to permit the cathode rays to exit the tube but a cardboard covering was added to protect the aluminium from damage by the strong electrostatic field that is necessary to produce the cathode rays. He knew the cardboard covering prevented light from escaping, yet Röntgen observed that the invisible cathode rays caused a fluorescent effect on a small cardboard screen painted with barium platinocyanide when it was placed close to the aluminium window. It occurred to Röntgen that the Hittorf-Crookes tube, which had a much thicker glass wall than the Lenard tube, might also cause this fluorescent effect. In the late afternoon of 8 November 1895, Röntgen carefully constructed a black cardboard covering similar to the one he had used on the Lenard tube. He covered the Hittorf-Crookes tube with the cardboard and attached electrodes to a Ruhmkorff coil to generate an electrostatic charge. As he passed the Ruhmkorff coil charge through the tube, he determined that the cover was light-tight and turned to prepare the next step of the experiment. Röntgen speculated that a new kind of ray might be responsible. In the following weeks he ate and slept in his laboratory as he investigated many properties of the new rays he temporarily termed X-rays. Nearly two weeks after his discovery, he took the very first picture using x-rays of his wife's hand, Anna Bertha. When she saw her skeleton she exclaimed "I have seen my death!" http://encarta.msn.com/encyclopedia_761555545/roentgen.html
 * [[image:rontgen_460.gif width="213" height="255" align="left"]]Wilhelm Röntgen 1845-1923**
 * [|http://en.wikipedia.org/wiki/Wilhem_]****[|Roentgen]

Henri Becquerel 1852-1908** Henri Becquerel (1852-1908) was born into a family of scientists. His grandfather had made important contributions in the field of electrochemistry while his father had investigated the phenomena of fluorescence and phosphorescence. He inherited the minerals and compounds discovered by his father. Once he learnt of Rontgen’s x-rays, which used fluorescents, he had a source of materials in which to conduct his own experiments. The material Becquerel chose was a double sulfate of uranium and potassium which he exposed to sunlight and placed on photographic plates wrapped in black paper. When developed, the plates revealed an image of the uranium crystals. He concluded "that the phosphorescent substance in question emits radiation which penetrates paper opaque to light”. When he intended to conduct another experiment, the skies proved to be cloudy, so Becquerel placed the plates into a draw. However, he was shocked to find fully developed images, proving that the uranium was emitting radiation without the help of outside sources. Becquerel had discovered radioactivity, the spontaneous emission of radiation by a material. Later, Becquerel demonstrated that the radiation emitted by uranium shared certain characteristics with x-rays but, unlike the latter, could be deflected by a magnetic field and therefore must consist of charged particles. This discovery earned him the Nobel Prize in 1903. http://www.physics.isu.edu/radinf/cuire.htm http://en.wikipedia.org/wiki/Henri_Becquerel

By the time Marie Sklodowska met her husband, Pierre Curie, he had established himself as a noteworthy scientist, discovering piezoelectricity whereby physical pressure applied to a crystal resulted in the creation of an electric potential. Together, the Curies furthered Becquerel’s discovery of radiation in uranium ore. The actual term of radioactivity was coined off by the Curies. After chemical extraction of uranium from the ore, Marie noted the residual material to be more "active" than the uranium itself. She concluded that the ore contained, in addition to uranium, new elements that were also radioactive. These discoveries led to her discovery of plutonium and radium. Four more years of processing tons of ore under oppressive conditions were required to isolate enough of each element to determine its chemical properties. For their work on radioactivity, the Curies were awarded the 1903 Nobel Prize in physics. Marie Curie died July 4, 1934, overtaken by pernicious anemia no doubt caused by years of overwork and radiation exposure. __http://www.cartage.org.lb/en/themes/Sciences/Physics/Atomicphysics/Atomicstructure/AtomicTimeline/AtomicTimeline.htm__ http://en.wikipedia.org/wiki/Marie_Curie
 * Marie Curie**[[image:curiess.jpg width="186" height="254" align="left"]] **1867-1934**

Frederick Soddy was born at Eastbourne, Sussex, England. He was educated at Eastbourne College and the University College of Wales, Aberystwyth. In 1895 he obtained a scholarship at Merton College, Oxford, from which University he graduated in 1898 with first class honours in chemistry. After two years of research at Oxford he went to Canada and from 1900 to 1902 was Demonstrator in the Chemistry Department of McGill University, Montreal. Here he worked with Professor Sir Ernest Rutherford on problems of radioactivity. Together they published a series of papers on radioactivity and concluded that it was a phenomenon involving atomic disintegration with the formation of new kinds of matter. Soddy then continued the study of radium emanation with Sir William Ramsay at University College, London. They were able to demonstrate that the element Helium was created by the radioactive decay of Radium Bromide. http://en.wikipedia.org/wiki/Frederick_Soddy http://nobelprize.org/nobel_prizes/chemistry/laureates/1921/soddy-bio.html
 * Frederick**[[image:soddyc2.gif width="184" height="210" align="left"]] **Soddy 1877-1956**

Hans Geiger was a German physicist who is most known as the co-inventor of the Geiger counter and the Geiger-Marsden experiment which discovered the atomic nucleus. In 1902 Geiger started studying physics and mathematics in University of Erlangen and was awarded a doctorate in 1906. In 1907, Geiger started working with Ernest Rutherford on Rutherford’s famous Gold Foil experiment. They also created the Geiger counter together, which is used to detect gamma, beta, and some alpha radiation particles. In 1911, Geiger started work with John Mitchell Nuttall discovering the Geige r-Nuttall law, which relates the decay constant of a radioactive  isotope with the energy of the alpha particles emitted. They performed experiments as well that led to Rutherford’s experiment. In 1928 Geiger and his student Walther Müller cr e ated an improved version of the Geiger counter, the Geiger-Müller counter. http://en.wikipedia.org/wiki/Hans_Geiger http://nobelprize.org/nobel_prizes/physics/laureates/1990/press.html
 * Hans Geiger 1882-1945**

Robert Millikan was born in the 1868, in Morrison, Illinois. After working for a short time as a court reporter, he entered Oberlin College (Ohio) in 1886. 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 - using for this purpose molten gold and silver at the U.S. Mint. Millikan spent a year (1895-1896) in Germany, at the Universities of Berlin and Göttingen. He returned at the invitation of A. A. Michelson, to become an assistant at the newly established Ryerson Laboratory at the University of Chicago. As a scientist, 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 elegant "falling-drop method". He also proved that this quantity was a constant for all electrons (1910), thus demonstrating the atomic structure of electricity. He also proved through experiment the Einstein’s photoelectric equation, and made the first direct photoelectric determination of Plank's constant. During 1920-1923, Millikan occupied himself with work concerning the hot-spark spectroscopy of the elements, 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. This ultimately led him to his significant studies of cosmic radiation using ionization chambers. http://nobelprize.org/nobel_prizes/physics/laureates/1923/millikan-bio.html http://en.wikipedia.org/wiki/Robert_Andrews_Millikan   **
 * [[image:milikan.jpg width="156" height="189"]]Robert Millikan 1868-1953**

Ernest Rutherford 1871-1937 ** New Zealander-English physicist who was born in Nelson, New Zealand, attended school in Nelson and Marlborough, and finished his tertiary education in Canterbury, New Zealand before traveling to England. Rutherford is best known for devising the names alpha  ,  beta   , and  gamma rays   to classify various forms of "rays", which were poorly understood at his time. Rutherford deflected alpha rays with both electric and magnetic fields in 1903. He also observed that the intensity of radioactivity   fell off with  time, and named the halving time the "  half-life   ”. In 1906, his students  Geiger   and Marsden conducted the classic gold foil  alpha particle   scattering experiment which showed large deflections for a small fraction of incident particles. This led Rutherford to propose that the atom was "nuclear." This meant that Rutherford has discovered a new idea of atomic structure. He proved that atoms are made up of tine balls and spaces. When the particles were shot at the gold foil, some particles passed through while others bounced off of the foil, meaning it hit a solid mass.   <span style="font-size: 90%; font-family: Tahoma,Geneva,sans-serif">    http://scienceworld.wolfram.com/biography/Rutherford.html http://en.wikipedia.org/wiki/Ernest_Rutherford

The Danish physicist Niels Bohr is known primarily for his pioneering work in the field of atomic theory. Bohr was born in Copenhagen and was educated at the University of Copenhagen at the time when Max Planck had just begun the development of Quantum Mechanics. After completing his dissertation on the electron theory of metals in 1911, Bohr went briefly to Cambridge and then on to Manchester, England, where he worked with Ernest Rutherford. Bohr discovered that Ernest Rutherford's idea of the structure of an atom had a few problems. He acknowledged that electrons existed at fixed levels of distance from the nucleus, and as long as they remain in these levels, the atom is stable. He also figured that when they change energy levels they give or take electrons, but that is the only time this occurs. If the electron gains energy, it would leap a level further from the nucleus, if it lessens in energy, the electron would fall a level closer to the nucleus. http://www2.lucidcafe.com/lucidcafe/library/95oct/nbohr.html http://en.wikipedia.org/wiki/Niels_Bohr
 * Niels Bohr 1885-1962**

The Austrian theoretical physicist Erwin Schrodinger published four papers that laid the foundation of the wave-mechanics approach to quantum theory and set forth his now-famous wave equation. Schrodinger earned a doctorate at the University of Vienna in 1910. In 1939 he joined the newly formed Institute for Advanced Studies in Dublin. There he continued his studies of the application and statistical interpretation of wave mechanics, the mathematical character of the new statistics, and the relationship of these statistics to statistical thermodynamics. Schrodinger’s development of wave mechanics became the second formula of quantum mechanics. His equation is similar to the mechanics of the atom as Newton’s equations of motions bear to planetary astronomy. [|http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Schrodinger.html] http://en.wikipedia.org/wiki/Erwin_Schrodinger
 * Erwin Schrodinger 1887-1961**[[image:Erwin_schrodinger1.jpg width="201" height="232" align="left"]]

Otto Hahn was a German chemist who received the 1944 Nobel Prize in Chemistry for discovering nuclear fission. He is considered a pioneer of radioactivity and radiochemistry. Glenn T. Seaborg deemed Hahn "the father of nuclear chemistry". Jointly with Lise Meitner and his pupil and assistant Fritz Strass mann (1902-1980), Otto Hahn furthered the research begun by Enrico Fermi and his team in 1934 when they bombarded uranium with neutrons. In December 1938, when Hahn and Strassmann looked for transuranium elements in a uranium sample that had been bombarded with neutrons, they found traces of barium. The barium was detected by the use of an organic barium salt. On the evidence of the decisive experiment on 17 December 1938 (the celebrated "radium-barium-mesothorium-fractionation"), Otto Hahn concluded that the uranium nucleus had "burst" into atomic nuclei of medium weight. This was the discovery of nuclear fission. http://en.wikipedia.org/wiki/Otto_Hahn http://www.atomicarchive.com/Bios/Hahn.shtml
 * Otto Hahn 1879-1968**

Heisenberg is another great discoverer of quantum mechanics and is most known for the uncertainty principle in quantum theory. This principle states, “The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa.” This is a statement between the position and the momentum of a subatomic particle, such as an electron. This relation has profound implications for such fundamental notions as causality and the determination of the future behavior of an atomic particle. This statement is a huge part of “matrix mechanics” and led Heisenberg to be appointed as director-in-residence for the KWIP, the “uranium club” effort of Germany during WWII http://en.wikipedia.org/wiki/Werner_Heisenberg http://www.aip.org/history/heisenberg/p08.htm
 * [[image:Werner_2.jpg width="155" height="169" align="left"]]Werner Heisenberg 1901-1976**[[image:heisenberg_uncertainty_principle.gif width="153" height="185" align="right"]]

James Chadwick, who was knighted by the queen, was an English physicist and Nobel laureate in physics awarded for his discovery of the neutron. Using alpha particles discovered a neutral atomic particle with a mass close to a proton. In contrast with the helium nuclei ( alpha particles ) which are positively charged, and therefore repelled by the considerable electrical forces present in the nuclei of heavy atoms, this new tool in atomic disintegration need not overcome any Coulomb barrier and is capable of penetrating and splitting the nuclei of even the heaviest elements. In this way, Chadwick prepared the way towards the fission of uranium 235. In 1940, Chadwick forwarded the work of two French scientists to the Royal Society, believing that the papers were not acceptable during the war. In 2007, the papers were read during the discovery of documents in the archives. Chadwick was also part of the Manhattan Project, which created the nuclear bombs that were dropped on Japan. http://en.wikipedia.org/wiki/James_Chadwick [|http://nobelprize.org/nob][|el_prizes/physics/laureates/1935/chadwick-bio.html]
 * [[image:chadwick.jpg width="134" height="183" align="left"]]James Chadwick 1891-1974**