Fall.2010.MMA.Como.Mello.atomictimeline

=Atomic History Timeline= Ancient Times (450 AD and years prior) Aristotle - Unknown Aristotle was born in Greece in 384 BC. He was a student of Plato and a teacher to Alexander the Great. He helped further a lot of things in science. As well as adding to the chemistry and physical world he founded a way of classifying animals. He died in 322 BC. He did not like the idea that atoms were the smallest thing in the universe. He believed that nothing was smaller than the things that made up the natural elements, earth, water and fire. Although we know that this is true now, people then believed him over Leucippus and Democritis just because people liked Aristotle more. [] Leucippus - Unknown Leucippus was born in the first half of the 5th century BCE in Greece. His exact dates of birth and death are not known. All that is known is that he lived in the 5th century CE. While not much is known about Leucippus, it is known that he was the developer of atomism. (Thebigview.com) Most of Leucippus' theories were established by a later scientist, Democritus. Between 440 BCE and 430 BCE, Luccippus developed a school in Abdera where he met Democritus. It is difficult for historians to determine what Leucippus discovered and what Democritus discovered. Even though not much is known about Leucippus' life and other studies, it is certain that he developed the fundamental idea of the atom, which was the reason for the further exploration of the atom. (Britanica) []

Democritus Unknown Democritis was born in Greece in a town called Abdera, located on the coast of the Aeagean Sea in 494 BCE. He worked closely with Leucippus, with Leucippus being his mentor. Before he died in 404 BCE he was a leader in the chemistry world. (Gossin) He is very important in the history of the atom because he introduced the concept of the atom. Although Leucippus was the first to come up with the concept Democritus came up with the atomic theary which put the idea into form. Democritis worked with Leucippus to completely overturn everything that the science world believed in. They came up with the terms which are still used today. (thebigview.com) [|www.mlahanas.de/Greeks/] Bios/Democritus.html 450-1700 (extra credit only, not actually necessary) Roger Bacon - Bacon performed and described various experiments, which were for a time claimed as the first instances of true experimental science, several hundred years before the rise of science in the West. This widely held interpretation of Bacon as a modern experimental scientist, emerging before his time, originated in the nineteenth century. This image reflected the emphasis, dominant at that time, upon experiment as the principal form of scientific activity and the general acceptance of the characterization of the Middle Ages as the "Dark Ages". Some writers of this period, such as Andrew Dickson White, carried the account further by describing a concerted opposition to Bacon's ideas in which he was repeatedly persecuted and imprisoned as part of a medieval "Warfare of Science with Theology". [] Robert Boyle - January 25, 1627 - December 31, 1691 Robert Boyle is the most influential Anglo-Irish scientist in history. He played a key role in the history of science by establishing the experimental method, on which all modern science is based (Mollan). Also, with his assistant Robert Hooke, he began pioneering experiments on the properties of gases, including those expressed in Boyle's law. He demonstrated the physical characteristics of air, showing that is is necessary in combustion, respiration, and sound transmission. He also wrote The Sceptical Chymist in 1661, in which he attacked Aristotle's theory of four elements. This was an essential part of the modern theory of chemical elements. [] Sir Isaac Newton - January 4, 1643 - March 20, 1727 As mathematician, Newton invented integral calculus, and jointly with Leibnitz, differential calculus. He also calculated a formula for finding the velocity of sound in a gas which was later corrected by Laplace. Newton made a huge impact on theoretical astronomy. He defined the laws of motion and universal gravitation which he used to predict precisely the motions of stars, and the planets around the sun. Using his discoveries in optics Newton constructed the first reflecting telescope. Newton found science a hodgepodge of isolated facts and laws, capable of describing some phenomena, but predicting only a few. He left it with a unified system of laws that can be applied to an enormous range of physical phenomena, and that can be used to make exact predications. Newton published his works in two books, namely "Opticks" and "Principia." [] 1700-1800 Joseph Black - April 16, 1728 - December 6, 1799 It is during the early Glasgow years (1750-52) that it seems Black began his work on the chemistry of "magnesia alba" (a basic magnesium carbonate), which he later submitted for his MD thesis in Edinburgh, and which includes the discovery of what we now call carbon dioxide - he called it "fixed air". These experiments involved the very first careful gravimetric (weight) measurements on changes brought about when heating magnesia alba (with release of CO2) and reacting the products with acids or alkalis. This foreshadowed Lavoisier's work, and laid the foundation for modern chemistry. (Because this work was submitted for a medical degree, Black also felt obliged to include a section on magnesia alba as a purgative and antacid.) [] Antoine Lavoisier - August 26, 1743 - May 8, 1774 (guillotined) French chemist who, through a conscious revolution, became the father of modern chemistry. As a student, he stated "I am young and avid for glory." He was educated in a radical tradition, a friend of Condillac and read Maqueses dictionary. He won a prize on lighting the streets of Paris, and designed a new method for preparing saltpeter. He also married a young, beautiful 13-year-old girl named Marie-Anne, who translated from English for him and illustrated his books. Lavoisier demonstrated with careful measurements that transmutation of water to earth was not possible, but that the sediment observed from boiling water came from the container. He burnt phosphorus and sulfur in air, and proved that the products weighed more than he original. Nevertheless, the weight gained was lost from the air. Thus he established the Law of Conservation of Mass. [] Henry Cavendish - October 10, 1731 - February 24, 1810 The English chemist and physicist Henry Cavendish was the first to recognize hydrogen gas as a distinct substance. He also described the composition of water and made the first accurate measurement of the density of the Earth. Cavendish approached most of his investigations through quantitative measurements. In order to establish that hydrogen gas was a substance entirely different from ordinary air, he calculated their densities as well as the densities of several other gases. He found that common air, as well as air brought by a balloon from the upper atmosphere, is made up of nitrogen in a 4:1 ratio by volume. He also showed that water is composed of oxygen and hydrogen. He measured heats of fusion and evaporation as well as specific heats and those of the mixing of solutions in water. Cavendish's measurements of the freezing points of various solutions showed the existence of compositions that yield maximum and minimum freezing points. []

1800-1875 Lord Kelvin - June 26, 1824 - December 17, 1907 Kelvin argued that the key issue in the interpretation of the Second Law of Thermodynamics was the explanation of irreversible processes. He noted that if entropy always increased, the universe would eventually reach a state of uniform temperature and maximum entropy from which it would not be possible to extract any work. He called this the Heat Death of the Universe. With Rankine he proposed a thermodynamical theory based on the primacy of the energy concept, on which he believed all physics should be based. He said the two laws of thermodynamics expressed the indestructibility and dissipation of energy. He also tried to demonstrate that the equipartition theorem was invalid. [] Wilhelm C Rontgen - March 27, 1845 - February 10, 1923 In 1894 Röntgen had turned his attention to cathode rays and by late 1895 he was investigating the fluoresence caused by these rays using a Crookes tube. In order to direct a pencil of rays onto a screen, he covered a discharge tube with black cardboard and operated it in a darkened room. Röntgen noticed by chance a weak light on a nearby bench and found that another screen, coated with barium platinocyanide, was fluorescing during the experiment. He had already established that cathode rays could not travel more than a few centimeters in air, and as the screen was about a meter from the discharge tube he realized that he had discovered a new phenomenon. During the succeeding six weeks he devoted himself, feverishly and exclusively, to investigating the properties of the new emanations, which, because of their unknown nature, he called ‘x-rays’. On 28 December 1895 he announced his discovery and gave an accurate description of many of the basic properties of the rays: they were produced by cathode rays (electrons) at the walls of the discharge tube; they traveled in straight lines and could cause shadows; all bodies were to some degree transparent to them; they caused various substances to fluoresce and affected photographic plates; they could not be deflected by magnetic fields. Röntgen concluded that x-rays were quite different from cathode rays but seemed to have some relationship to light rays. He conjectured that they were longitudinal vibrations in the ether (light was known to consist of transverse vibrations). Their true nature was finally established in 1912. []

John Dalton - September 6, 1766 - July 27, 1844 During his residence in Kendal, Dalton had contributed solutions of problems and questions on various subjects to the Gentlemen's and Ladies' Diaries, and in 1787 he began to keep a meteorological diary in which during the succeeding fifty-seven years he entered more than 200,000 observations. His first separate publication was Meteorological Observations and Essays (1793), which contained the germs of several of his later discoveries; but in spite of the originality of its matter, the book met with only a limited sale. Another work by him, Elements of English Grammar, was published in 1801. In 1794 he was elected a member of the Manchester Literary and Philosophical Society, and a few weeks after election he communicated his first paper on "Extraordinary facts relating to the vision of colours," in which he gave the earliest account of the optical peculiarity known as Daltonism or color-blindness, and summed up its characteristics as observed in himself and others. Besides the blue and purple of the spectrum he was able to recognize only one color, yellow, or, as he says in his paper, "that part of the image which others call red appears to me little more than a shade or defect of light; after that the orange, yellow and green seem one color which, descends pretty uniformly from an intense to a rare yellow, making what I should call different shades of yellow." This paper was followed by many others on diverse topics -- on rain and dew and the origin of springs, on heat, the color of the sky, steam, the auxiliary verbs and participles of the English language and the reflection and refraction of light. In 1800 he became a secretary of the society. []

1875-1900 JJ Thomson - The Plum Pudding Model December 18, 1856 - August 30, 1940 Thomson's early interest in atomic structure was reflected in his Treatise on the Motion of Vortex Rings which won him the Adams Prize in 1884. His application of Dynamics to Physics and Chemistry appeared in 1886, and in 1892 he had his Notes on Recent Researches in Electricity and Magnetism published. This latter work covered results obtained subsequent to the appearance of James Clerk Maxwell's famous "Treatise" and it is often referred to as "the third volume of Maxwell". Thomson co-operated with Professor J. H. Poynting in a four-volume textbook of physics, Properties of Matter and in 1895 he produced Elements of the Mathematical Theory of Electricity and Magnetism, the 5th edition of which appeared in 1921. In 1896, Thomson visited America to give a course of four lectures, which summarised his current researches, at Princeton. These lectures were subsequently published as Discharge of Electricity through Gases (1897). On his return from America, he achieved the most brilliant work of his life - an original study of cathode rays culminating in the discovery of the electron, which was announced during the course of his evening lecture to the Royal Institution on Friday, April 30, 1897. His book, Conduction of Electricity through Gases, published in 1903 was described by Lord Rayleigh as a review of "Thomson's great days at the Cavendish Laboratory". A later edition, written in collaboration with his son, George, appeared in two volumes (1928 and 1933). []

Henri Becquerel - December 15, 1852 - August 25, 1908 Becquerel's earliest work was concerned with the plane polarization of light, with the phenomenon of phosphorescence and with the absorption of light by crystals (his doctorate thesis). He also worked on the subject of terrestrial magnetism. In 1896, his previous work was overshadowed by 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. []

Marie Curie - November 7, 1867 - July 4, 1934 Curies early researches, together with her husband, were often performed under difficult conditions, laboratory arrangements were poor and both had to undertake much teaching to earn a livelihood. The discovery of radioactivity by Henri Becquerel in 1896 inspired the Curies in their brilliant researches and analyses which led to the isolation of polonium, named after the country of Marie's birth, and radium. Mme. Curie developed methods for the separation of radium from radioactive residues in sufficient quantities to allow for its characterization and the careful study of its properties, therapeutic properties in particular. Curie throughout her life actively promoted the use of radium to alleviate suffering and during World War I, assisted by her daughter, Irene, she personally devoted herself to this remedial work. She retained her enthusiasm for science throughout her life and did much to establish a radioactivity laboratory in her native city - in 1929 President Hoover of the United States presented her with a gift of $ 50,000, donated by American friends of science, to purchase radium for use in the laboratory in Warsaw. []

1900-1915 Erwin Schrodinger - August 12, 1889 - January 4, 1961 Schrodingers papers at that time dealt with specific heats of solids, with problems of thermodynamics (he was greatly interested in Boltzmann's probability theory) and of atomic spectra; in addition, he indulged in physiological studies of colour (as a result of his contacts with Kohlrausch and Exner, and of Helmholtz's lectures). His great discovery, Schrödinger's wave equation, was made at the end of this epoch-during the first half of 1926. It came as a result of his dissatisfaction with the quantum condition in Bohr's orbit theory and his belief that atomic spectra should really be determined by some kind of eigenvalue problem. For this work he shared with Dirac the Nobel Prize for 1933. []

Ernest Rutherford - August 30, 1871 - October 19, 1937 In Manchester, Rutherford did research on the properties of the radium emanation and of the alpha rays and, in conjunction with H. Geiger, a method of detecting a single alpha particle and counting the number emitted from radium was devised. In 1910, his 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. [] Robert Millikan - March 22, 1868 - December 19, 1953 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. 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). []

1915-1950 Werner Heisenberg - December 5, 1901 - February 1 1976 Heisenberg's name will always be associated with his theory of quantum mechanics, published in 1925, when he was only 23 years old. For this theory and the applications of it which resulted especially in the discovery of allotropic forms of hydrogen, Heisenberg was awarded the Nobel Prize for Physics for 1932. His new theory was based only on what can be observed, that is to say, on the radiation emitted by the atom. We cannot, he said, always assign to an electron a position in space at a given time, nor follow it in its orbit, so that we cannot assume that the planetary orbits postulated by Niels Bohr actually exist. Mechanical quantities, such as position, velocity, etc. should be represented, not by ordinary numbers, but by abstract mathematical structures called "matrices" and he formulated his new theory in terms of matrix equations. Later Heisenberg stated his famous principle of uncertainty, which lays it down that the determination of the position and momentum of a mobile particle necessarily contains errors the product of which cannot be less than the quantum constant h and that, although these errors are negligible on the human scale, they cannot be ignored in studies of the atom. []

Neils Bohr- October 7, 1885 - November 18, 1962 In 1913 Bohr published a classic paper, on the constitution of atoms and molocules, in which he used the quantum of energy, h, introduced into physics by Max Planck in 1900, to rescue Rutherford's account of atomic structure from a vital objection and also to account for the line spectrum of hydrogen. The first problem Bohr faced was to explain the stability of the atom. Rutherford's 1911 model of the atom with electrons orbiting a central nucleus (The so-called planetary model) was Theoretically unstable. This was because, unlike planets orbiting the Sun, electrons are charged particles, which, according to classical physics, should radiate energy and consequently spiral in toward the nucleus. []

James Chadwick- October 20, 1891 - July 24,1974 In 1932, Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons - elementary particles devoid of any electrical charge. In contrast with the helium nuclei (alpha rays) which are 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 electric barrier and is capable of penetrating and splitting the nuclei of even the heaviest elements. Chadwick in this way prepared the way towards the fission of uranium 235 and towards the creation of the atomic bomb. For this epoch-making discovery he was awarded the Hughes Medal of the Royal Society in 1932, and subsequently the Nobel Prize for Physics in 1935. []

1950-current (extra credit only, not actually necessary for the project) Leonard Hayflick- Born-May 20, 1928 In 1961, Leonard Hayflick and his colleague cytogeneticist Paul Moorhead conducted a series of definitive experiments in which they were able to demonstrate that normal human somatic cells have a finite number of replicative cycles. Today this phenomenon is known as the Hayflick Limit. In order to rule out any technical errors due to methodology or contamination, the two scientists mixed equal numbers of male cells, that had replicated many times, with female cells that had only replicated a few times. Unmixed cell cultures were used as controls. Once the male control cells stopped replicating they examined the mixed population of cells and found only female cells left. The results of this experiment disputed accepted dogma of the time that all normal vertebrate cells grown in culture were immortal and to this day there are still some skeptical scientists. [] George Otto Gey- July 6, 1899 - November 8, 1970 In1930 George Otto Gey was living on Saint Paul Street in Baltimore, and in the 1950s he started the Tissue Culture Laboratory at Johns Hopkins University. Using a sample from the cervix of the Henrietta Lacks provided by Dr. Wharton, he propagated her cells into an immortalized human cell line. George Gey is also credited for creating the roller drum. This machine was one of the first to help nurture cell cultures. The roller drum consisted of various holes where tissues and their appropriate growth substances were allocated. The drum spun in order to mix the substances and once an hour allow the cultures to be exposed to the environment until the drum rolled again and rebathed the cells in liquid. Gey is also noted to be one of the first to document cell division and growth on film. He devised a time lapse camera with temperature controlled incubator that stood twelve feet in length from spare parts at a nearby junkyard. In his spare time, he enjoyed climbing and mountain biking. []

Kary Mullis - Born- December 28, 1944 Mullis received a Bachelor of Science degree in chemistry from the Georgia Institute of Technology in 1966. He earned a Ph.D. degree in biochemistry from the University of California, Berkeley, in 1972 and lectured in biochemistry there until 1973. That year, Kary became a postdoctoral fellow in pediatric cardiology at the University of Kansas Medical School, with emphasis in the areas of angiotensin and pulmonary vascular physiology. In 1977 he began two years of postdoctoral work in pharmaceutical chemistry at the University of California, San Francisco. Kary joined the Cetus Corporation in Emeryville, California, as a DNA chemist in 1979. During his seven years there, he conducted research on oligonucleotide synthesis and invented the polymerase chain reaction. Mullis received the Nobel Prize in Chemistry for his invention of the polymerase chain reaction. This was a method of amplifying DNA, PCR multiples a single, microscopic strand of the genetic material billions of times within hours. [] Explanation of Models The Plum Pudding Model of an Atom The plum pudding model of the atom by J.J. Thompson, who discovered the electron in 1897, was proposed in 1904 before the discovery of the atomic nucleus. In this model, the atom is composed of electrons surrounded by a soup of positive charge to balance the electrons' negative charges, like negatively-charged plums surrounded by positively-charged pudding. [] The Rutherford-Bohr Model The Rutherford-Bohr Model, devised by Neils Bohr, depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system. This was an improvement from the earlier simple based models. Since the Bohr model is a quantum physics-based modification of the Rutherford model, many sources combine the two, referring to the Rutherford-Bohr Model. [] The Planetary Model The Bohr Model or planetary model of the atom is used as a symbol for atomic energy. In the Bohr Model the neutrons and protons (symbolized by red and blue balls in the adjacent image) occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the sun but the orbits are not confined to a plane as is approximately true in the solar system. [] The Electron Cloud Model An electron cloud is a visual model of the most probable locations of electrons in an atom. The cloud is denser where you will probably find an electron. The electron cloud model is used to describe the possible locations of electrons around the nucleus. []