Fall.2008.MMA.Naylor.Foster.Timeline


 * __ Ancient Scientist  __**

**Democritus** __ Born __ : 460 B.C. __ Died __ : 370 B.C. __ Birth Place __ : Thrace, Greece __ Discovery __ : Democritus did not originate the atomic theory; he learned it from its founder, Leucippus. He hypothesized that all matter (plus space and time) is composed of tiny indestructible units, called atoms. These atoms remain unchanged, but move about in space to combine in various ways to form all macroscopic objects, they cluster together to form things that are conceivable. Differences in shape, arrangement, and position of atoms produce different things. We see changes in things because of the rearrangement of atoms, but atoms themselves are eternal. __ Biography __ : He was described as well traveled, probably visiting Babylon, Egypt, and Ethiopia, and perhaps India. He appears to have spent all of his time on scientific and philosophical studies, teaching, and writing— some 60 works have been listed. Of his voluminous writings, only a few fragments of his ethical theory remain. But these fragments and the descriptions by other writers of his atomic theory put him among the foremost thinkers of his time. __Born__: 620 BCE __Died__: 546 BCE __Birth Place__: Miletus, Greek Ionia __Discovery__: Before Thales, the Greeks explained the origin and nature of the world through [|myths] of [|anthropomorphic] [|gods] and [|heroes]. Phenomena such as [|lightning] or [|earthquakes] were attributed to actions of the gods. In contrast to these mythological explanations, Thales attempted to find [|naturalistic] explanations of the world, without reference to the [|supernatural]. He explained earthquakes by hypothesizing that the [|Earth] floats on water, and that earthquakes occur when the Earth is rocked by waves. Thales' most famous belief was his [|cosmological] doctrine, which held that the world originated from [|water]. [|Aristotle] considered this belief roughly equivalent to the later ideas of [|Anaximenes], who held that everything in the world was composed of [|air]. The intercept theorem is an important theorem in [|elementary geometry] about the ratios of various [|line segments], that are created if 2 intersecting [|lines] are intercepted by a pair of [|parallels]. It is equivalent to the theorem about ratios in [|similar triangles]. Traditionally it is attributed to Greek mathematician [|Thales], which is the reason why it is named theorem of Thales in some languages. __Biography__: There is considerable agreement that Thales was born in Miletus in Greek Ionia in the mid 620s BCE and died in about 546 BCE, but even those dates are indefinite. [|Aristotle], the major source for Thales's philosophy and science, identified Thales as the first person to investigate the basic principles, the question of the originating substances of matter and, therefore, as the founder of the school of natural philosophy. Thales was interested in almost everything, investigating almost all areas of knowledge, philosophy, history, science, mathematics, engineering, geography, and politics. He proposed theories to explain many of the events of nature, the primary substance, the support of the earth, and the cause of change. Thales was much involved in the problems of astronomy and provided a number of explanations of cosmological events which traditionally involved supernatural entities. His questioning approach to the understanding of heavenly phenomena was the beginning of Greek astronomy. Thales's hypotheses were new and bold, and in freeing phenomena from godly intervention, he paved the way towards scientific endeavour. He founded the Milesian school of natural philosophy, developed the scientific method, and initiated the first western enlightenment. A number of anecdotes is closely connected to Thales's investigations of the cosmos. When considered in association with his hypotheses they take on added meaning and are most enlightening. Thales was highly esteemed in ancient times, and a letter cited by Diogenes Laertius, and purporting to be from Anaximenes to Pythagoras, advised that all our discourse should begin with a reference to Thales (D.L. II.4). __Born__: 384 BCE __Died__: 322 BCE __Birth Place__: Stagirus, Greece __Discovery__: //First//, Aristotle argues, forms are powerless to explain //changes// of things and a thing's ultimate extinction. Forms are not causes of movement and alteration in the physical objects of sensation. //Second//, forms are equally incompetent to explain how we arrive at //knowledge// of particular things. For, to have knowledge of a particular object, it must be knowledge of the substance which is //in// that things. However, the forms place knowledge outside of particular things. Further, to suppose that we know particular things better by adding on their general conceptions of their forms, is about as absurd as to imagine that we can count numbers better by multiplying them. Finally, if forms were needed to explain our knowledge of particular objects, then forms must be used to explain our knowledge of objects of art; however, Platonists do not recognize such forms. The //third// ground of attack is that the forms simply cannot explain the //existence// of particular objects. Plato contends that forms do not exist //in// the particular objects which partake in the forms. However, that substance of a particular thing cannot be separated from the thing itself. Further, aside from the jargon of "participation," Plato does not explain the relation between forms and particular things. In reality, it is merely metaphorical to describe the forms as patterns of things; for, what is a genus to one object is a species to a higher class, the same idea will have to be both a form and a particular thing at the same time. Finally, on Plato's account of the forms, we must imagine an intermediate link between the form and the particular object, and so on //ad infinitum//: there must always be a "third man" between the individual man and the form of man. __ Biography __ : Aristotle was born in 384 BCE. at Stagirus, a Greek colony and seaport on the coast of Thrace. His father Nichomachus was court physician to King Amyntas of Macedonia, and from this began Aristotle's long association with the Macedonian Court, which considerably influenced his life. While he was still a boy his father died. At age 17 his guardian, Proxenus, sent him to Athens, the intellectual center of the world, to complete his education. He joined the Academy and studied under Plato, attending his lectures for a period of twenty years. In the later years of his association with Plato and the Academy he began to lecture on his own account, especially on the subject of rhetoric. At the death of Plato in 347, the pre-eminent ability of Aristotle would seem to have designated him to succeed to the leadership of the Academy. But his divergence from Plato's teaching was too great to make this possible, and Plato's nephew Speusippus was chosen instead. At the invitation of his friend Hermeas, ruler of Atarneus and Assos in Mysia, Aristotle left for his court. He stayed three year and, while there, married Pythias, the niece of the King. In later life he was married a second time to a woman named Herpyllis, who bore him a son, Nichomachus. At the end of three years Hermeas was overtaken by the Persians, and Aristotle went to Mytilene. At the invitation of Philip of Macedonia he became the tutor of his 13 year old son Alexander (later world conqueror); he did this for the next five years. Aristotle's work being finished, he returned to Athens, which he had not visited since the death of Plato. He found the Platonic school flourishing under Xenocrates, and Platonism the dominant philosophy of Athens. He thus set up his own school at a place called the [|Lyceum]. When teaching at the Lyceum, Aristotle had a habit of walking about as he discoursed. It was in connection with this that his followers became known in later years as the //peripatetics//, meaning "to walk about." For the next thirteen years he devoted his energies to his teaching and composing his philosophical treatises. He is said to have given two kinds of lectures: the more detailed discussions in the morning for an inner circle of advanced students, and the popular discourses in the evening for the general body of lovers of knowledge. At the sudden death of Alexander in 323 BCE., the pro-Macedonian government in Athens was overthrown, and a general reaction occurred against anything Macedonian. A charge of impiety was trumped up against him. To escape prosecution he fled to Chalcis in Euboea so that (Aristotle says) "The Athenians might not have another opportunity of sinning against philosophy as they had already done in the person of Socrates." In the first year of his residence at Chalcis he complained of a stomach illness and died in 322 BCE.
 * Thales of Miletus **[[image:http://www.britannica.com/blogs/wp-content/uploads/2007/10/thales.jpg width="160" height="209" caption="http://www.britannica.com/blogs/wp-content/uploads/2007/10/thales.jpg"]]
 * Aristotle** [[image:http://kids.niehs.nih.gov/images/aristotle.jpg width="167" height="202" caption="http://kids.niehs.nih.gov/images/aristotle.jpg"]]

**__1700-1800__**


 * Sir Isaac Newton**
 * DOB-DOD:** 4 January 1642-31 March 1727
 * Birthplace:** Woolsthorpe, near Grantham in Lincolnshire, England
 * Discovery:** Newton argued that white light is really a mixture of many different types of rays, that the different types of rays are refracted at slightly different angles, and that each different type of ray is responsible for producing a given spectral color. A so-called crucial experiment confirmed the theory. Newton selected out of the spectrum a narrow band of light of one color. He sent it through a second prism and observed that no further elongation occurred. All the selected rays of one color were refracted at the same angle.
 * The Life of Sir Isaac Newton:** Newton came from a family of modest yeoman farmers. His father died several months before he was born. Three years later his mother remarried and moved to a nearby village, leaving Isaac in the care of his maternal grandmother. Upon the death of his stepfather in 1656, Newton's mother removed him from grammar school in Grantham in hopes of training him to manage her now much enlarged estate, but even then Newton's interests ran more toward books and mathematical diversions. His family decided that he should be prepared for the university, and he entered Trinity College, Cambridge, in June 1661. [|http://www.chemistry.mtu.edu/~pcharles/SCIHISTORY/Newton.html].

Joseph Priestly** http://www.spaceship-earth.de/Biograph/Priestley.htm.
 * [[image:http://www.creationism.org/books/TaylorInMindsMen/TaylorIMMccJosephPriestleyM.jpg width="208" height="326"]]
 * DOB-DOD:** 13 March 1733-6 February 1804
 * Birthplace:** Birstall Fieldhead, near Leeds, Yorkshire, England
 * Discovery:** Priestley's most famous discovery occurred on Aug. 1, 1774, when he obtained a colorless gas by heating red mercuric oxide (he called it //mercurius calcinatus per se//). Finding that a candle would burn in it "with a remarkably vigorous flame," he called it "dephlogisticated air" because he believed, accepting prevailing theory, that ordinary air became saturated with phlogiston when it could no longer support combustion or life. (Phlogiston was thought to be a material that was transferred during burning and respiration; a unifying idea in 18th-century chemistry, it avoided quantitative considerations but was the reverse of the oxidative interpretation of combustion and respiration established by Lavoisier in 1789.) Priestley was not yet sure, however, that he had discovered a "new species of air."
 * Life of Joseph Priestly:** Priestley was the oldest of six children of a modestly successful cloth dresser. For several years during his childhood Joseph was often sickly, but, perhaps as compensation, he became an avid learner on his own. With improving health, in 1752 he entered a new Dissenting Academy at Daventry, Northamptonshire, one of the educational institutions that, in the 18th century, was established independently by Nonconformists. These academies offered high-quality education and attracted the best teachers and students. In 1758 Priestley transferred to a more sympathetic congregation in Nantwich, Cheshire, where he opened a day school with 36 students. Becoming interested in science at this time, he provided them with "philosophical instruments," such as an air pump and a static generator for electrical demonstrations. His teaching success led to his appointment in 1761 as a tutor in language and literature at Warrington Academy in Lancashire. Because the universities and learned professions were closed to Dissenters, Priestley developed new courses that were suitable for students preparing for careers in industry and commerce. Textbooks were not available, and these he set himself to write. In 1761 he published the //Rudiments of English Grammar,// a work that was radical in its reliance on description of actual English usage as opposed to prescription on the basis of dead classical languages; it remained in use for 50 years. Ordained a Dissenting minister in 1762 at Warrington, in the same year he married Mary Wilkinson, aged 18, the only daughter of an ironmaster at Bersham in Wales. They had a daughter and three sons.

Antoine-Laurent de** **Lavoisier**
 * [[image:http://content.answers.com/main/content/img/scitech/HSantoin.jpg width="225" height="325"]]
 * DOB-DOD:** 26 August 1743 – 8 May 1794
 * Birthplace:** Paris, France


 * Discovery:** Lavoisier's researches included some of the first truly quantitative chemical experiments. He carefully weighed the reactants and products in a chemical reaction, which was a crucial step in the advancement of chemistry. He showed that, although matter can change its state in a chemical reaction, the quantity of matter is the same at the end as at the beginning of every chemical change. These experiments supported the law of conservation of mass.

http://en.wikipedia.org/wiki/Antoine_Lavoisier.
 * Life of Antoine-Laurent de Lavoisier:** H e attended the College Mazarin from 1754 to 1761, studying chemistry, botany, astronomy, and mathematics. His education was filled with the ideals of the French Enlightenment of the time, and he felt fascination for Maquois's dictionary. From 1761 to 1763, he studied some law at the University of Paris where he received his Bachelor of Law in 1763. At the same time, he continued attending lectures in the natural sciences. Lavoisier's devotion and passion for chemistry was largely influenced by Etienne Condillac, a prominent French scholar of the 18th century. In 1771, Lavoisier at age 28, married the 13-year-old Marie-Anne Pierrette Paulze, the daughter of a co-owner of the Ferme. Over time, she proved to be a scientific colleague to her husband.

__**
 * __ 1800-1875
 * John Dalton**
 * DOB-DOD:** 6 September 1766 – 27 July 1844
 * Place of Origin:** Eaglesfield, England

Discovery: His theory was based on three important propositions. The first was that all matter is composed of extremely small, indivisible, and indestructible particles called atoms. The second was that the atoms of one element are all exactly alike in every respect including weight but are different from the atoms of every other element. The last was that when elements combine to form compounds their atoms combine in simple numerical proportions such as one to one, two to one, and four to three. The ideas of atoms had been suggested centuries earlier by the Greek philosopher Democritus, so the concept was not entirely unfamiliar to Dalton's contemporaries. But Dalton's complete formulation of a consistent theory was a breakthrough. One of the most important features of the theory was its proposal that atoms differed from each other by weight. This was something measurable, making Dalton's the first quantitative atomic theory ever advanced. http://en.wikipedia.org/wiki/John_Dalton. http://www.robinsonlibrary.com/science/chemistry/biography/dalton.htm.
 * Life of John Dalton:** Dalton was born into a Quaker family at Eaglesfield, near Cockermouth in Cumbria, England. The son of a weaver, he joined his older brother Jonathan at age 15 in running a Quaker school in nearby Kendal. Around 1790 Dalton seems to have considered taking up law or medicine, but his projects were not met with encouragement from his relatives — Dissenters were barred from attending or teaching at English universities — and he remained at Kendal until, in the spring of 1793, he moved to Manchester. Mainly through John Gough, a blind philosopher and Polymath from whose informal instruction he owed much of his scientific knowledge, Dalton was appointed teacher of mathematics and natural philosophy "New College" in Manchester, a Dissenting academy. He remained in that position until 1800, when the college's worsening financial situation led him to resign his post and begin a new career in Manchester as a private tutor for mathematics and natural philosophy.

__Born__: 1834 AD __Died__: 1907 AD __Birth Place__: Tobolsk, Siberia __Discovery:__ In the late ** 1860's **, Mendeleev began working on his great achievement: the periodic table of the elements. By arranging all of the ** 63 elements ** then known by their atomic weights, he managed to organize them into groups possessing similar properties. Where a gap existed in the table, he predicted a new element would one day be found and deduced its properties. And he was right. Three of those elements were found during his lifetime: gallium, scandium, and germanium. He derived his basic plan for his book from Gerhardt's theory of types, whereby elements were grouped by valence in relation to hydrogen. The typical elements hydrogen (1), oxygen (2), nitrogen (3), and carbon (4), were listed first, followed, in the same order, by the halogens (1) and alkali metals (1). Mendeleev's work towards The Principles of Chemistry led him to the // [|periodic law] //, which he formulated in March ** 1869 **: 'Elements placed according to the value of their atomic weights present a clear periodicity of properties' Based on this work Mendeleev was able to compose the first periodic table (as shown in the preface to Volume I), which remains strikingly similar to the first modern periodic table, devised by ** [|Moseley]  ** in ** 1914 **. Mendeleev was able to successfully predict the discovery of as yet undiscovered elements that would fit in according to his law, as demonstrated by the specific gaps he left in his table. First published in Russian in ** 1868 **, the English edition is based on the ** fifth Russian ** edition. "The periodic law is the focus of the work; beginning with the third edition it is more prominent because it had been verified experimentally. Mendeleev rewrote each edition, including all new scientific data-particularly confirmations of the periodic law-and reanalyzing difficulties that had arisen to hinder its confirmation (inert gases, radioactivity, radioactive and rare-earth elements)" __Biography:__ Born in Siberia, the last of ** at least 14 children **, Dmitri Mendeleev revolutionized our understanding of the properties of atoms and created a table that probably adorns every chemistry classroom in the world. After his father went blind and could no longer support the family, Mendeleev’s mother started a glass factory to help make ends meet. But just as Mendeleev was finishing high school, his father died and the glass factory burned down. With most of her other children now out on their own, his mother took her son to ** St. Petersburg **, working tirelessly and successfully to get him into college.
 * Dmitri Mendeleev **[[image:http://www.bluffton.edu/%7Ebergerd/NSC_111/images/Mendeleev.gif caption="http://www.bluffton.edu/~bergerd/NSC_111/images/Mendeleev.gif"]]

__ Born__: 1826 AD __Died__: 1911 AD __Birth Place__: Oakley Park, Ireland __Discovery__: Stoney is best known for his introduction of the term ‘electron’ into science. Although he is reported to have spoken of “an absolute unit of electricity” as early as 1874, his first public use of the term in print was in 1891 when he spoke of “these charges, which it will be convenient to call electrons” before the Royal Society of Dublin. Stoney published seventy-five scientific papers in a variety of journals, making significant contributions to cosmic physics and to the theory of gases. In [|1891], he proposed the term ' [|electron] ' to describe the fundamental unit of electrical charge, and his contributions to research in this area laid the foundations for the eventual discovery of the particle by [|J.J. Thomson] in [|1897]. He was elected a Fellow of the [|Royal Society] in [|1861], and served as Vice-President of the Society for 1898-9. Stoney's most important scientific work was the conception and calculation of the magnitude of the atom or particle of electricity, for which he coined the term " [|electron] ". He also estimated the number of [|molecules] in a cubic millimetre of gas, at room temperature and pressure, from data obtained from the kinetic theory of gases. He did however make substantial contributions to science in early [|spectroscopy]. He began, in 1868, by making a crucial distinction between two types of molecular motion. There was the motion of a molecule in a gas relative to other molecules, which Stoney was able to exclude as the cause of [|spectra]. There was also internal motion of a molecule, which according to Stoney produces the spectral lines. He went on to [|tackle], with little real success, the difficult problem of establishing an exact formula for the numerical relationship between the lines in the hydrogen spectrum. This problem was solved by the quantum theory of Niels Bohr. __Biography__: [|Irish] [|physicist] famous for introducing the term // [|electron] // in [|1874]. [|[1]] [|[2]] He worked at the [|National University of Ireland, Galway]. Stoney was born on [|15 February], [|1826] at Oak Park, near [|Birr] , [|County Offaly] , in the [|Irish midlands]. He attended [|Trinity College, Dublin], graduating with a B.A. in [|1848] and an M.A. in [|1852]. In [|1848] he became an assistant to the Earl of Rosse at Birr Castle, County Offaly, where Rosse had built and operated the 'Leviathan', the world's largest telescope in its day. In [|1852], Stoney became Professor of Natural Philosophy at [|Queen's College Galway] (now the [|National University of Ireland, Galway] ). In [|1857], he moved to Dublin as Secretary of the Queen's University; he subsequently became superintendent of Civil Service Examinations in Ireland, a post he held until his retirement in [|1893]. In this year, he took up residence in [|London].
 * George Stoney **[[image:http://understandingscience.ucc.ie/img/sc_George_Johnstone_Stoney.jpg caption="http://understandingscience.ucc.ie/img/sc_George_Johnstone_Stoney.jpg"]]
 * __ 1875-1900  __**

** Marie Curie** __ Born __ : 1867 A.C. __ Died __ : 1934 A.C. __ Birth Place __ : Warsaw, Russia __ Discovery ____ and Biography __ : Two mysterious discoveries led Marie Curie to her life’s work. In December 1895, a German physicist, Wilhelm Roentgen, had discovered rays that could travel through solid wood or flesh. A few months later a French physicist, Henri Becquerel, discovered that minerals containing uranium also gave off rays. Roentgen’s X-rays amazed scientists, who took to studying them with great energy. They mostly ignored Becquerel’s rays, which seemed much the same, only weaker. Marie decided to investigate the uranium rays. There was so little work on them for her to read about that she could begin experiments at once. First Marie needed a lab. She had to settle for a storeroom in the Paris Municipal School, where her husband, Pierre Curie, was now a professor. The storeroom was crowded and damp, but somehow she had to overcome its problems.

http://en.wikipedia.org/wiki/Wilhelm_Conrad_R%C3%B6ntgen.
 * Wilhem Conrad Roentgen**
 * DOB-DOD:** 27 March 1845-10 February 1923
 * Place of Origin:** Lennep in Rhenish, Prussia
 * Life of Wilhem C Roentgen:** Röntgen was born at Lennep (which is today a borough of Remscheid) in Rhenish Prussia as the only child of a merchant and manufacturer of cloth. His mother was Charlotte Constanze Frowein of Amsterdam. In March 1848, the family moved to Apeldoom 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. He was expelled for refusing to reveal the identity of a classmate guilty of drawing an unflattering portrait of one of the school's teachers. Not only was he expelled, he could not subsequently be admitted into any other Dutch or German gymnasium. In 1865, he tried to attend the University of Utrecht without having the necessary credentials required for a regular student. Hearing that he could enter the Federal Polytechnic Institute in Zurich, today the ETH Zurich, by passing its examinations, he began studies there as a student of mechanical engineering. In 1869, he graduated with a Ph.D. from the University of Zurich.
 * Discovery:** In the late afternoon of 8 November 1895, Röntgen determined to test his idea. He 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. Before setting up the barium platinocyanide screen to test his idea, Röntgen darkened the room to test the opacity of his cardboard cover. 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. It was at this point that Röntgen noticed a faint shimmering from a bench a meter away from the tube. To be sure, he tried several more discharges and saw the same shimmering each time. Striking a match, he discovered the shimmering had come from the location of the barium platinocyanide screen he had been intending to use next.


 * Antoine Henri Bacquerel**
 * DOB-DOD:** 15 December 1852-25 August 1908
 * Place of Origin:** Paris, France


 * Life of Henri Bacquerel:** His father, Alexander Edmond Becquerel, was a Professor of Applied Physics and had done research on solar radiation and on phosphorescence, while his grandfather, Antoine César, had been a Fellow of the Royal Society and the inventor of an electrolytic method for extracting metals from their ores. He 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. From 1878 he had held an appointment as an Assistant at the Museum of Natural History, taking over from his father in the Chair of Applied Physics at the Conservatoire des Arts et Metiers. 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.

http://nobelprize.org/nobel_prizes/physics/laureates/1903/becquerel-bio.html.
 * Discovery:** French physicist who was the son of physicist Edmond Becquerel, and father of physicist Jean Becquerel. In 1896, while investigating fluorescence in uranium salts, he accidentally discovered radioactivity in uranium-containing pitchblende by noting that the photographic plate upon which the pitchblende had been resting was fogged. Although he initially believed this to be a luminescence effect, his subsequent dissolving of the salt and recrystallization in total darkness showed that the luminecence was not involved. He also discovered that all uranium compounds (not just specific salts) fogged the plates, unlike luminescence which was confined to particular salts. The full impact of Becquerel's discovery was not appreciated, however, until the work of Marie and Pierre Curie, with whom he shared the 1903 Nobel Prize in physics.


 * Joseph John (J.J.) Thompson**
 * DOB-DOD:** 18 December 1856-30 August 1940
 * Place of Origin:** Manchester, England


 * Life of J. J. Thompson:** His father died when "J.J." was only sixteen. The young Thomson attended Owens College in Manchester, where his professor of mathematics encouraged him to apply for a scholarship at Trinity College, one of the most prestigious of the colleges at Cambridge University. Thomson won the scholarship, and in 1880 finished second in his class (behind Joseph Larmor) in the grueling graduation examination in mathematics. Trinity gave him a fellowship and he stayed on there, trying to craft mathematical models that would reveal the nature of atoms and electromagnetic forces.


 * Discovery:** J.J. Thompson, who discovered the electron in 1897, was proposed in 1904 before the discovery of the atomic nucleus. In this model, known as the “Plum Pudding” 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". The electrons (as we know them today) were thought to be positioned throughout the atom, but with many structures possible for positioning multiple electrons, particularly rotating rings of electrons (see below). Instead of a soup, the atom was also sometimes said to have had a cloud of positive charge.


 * __ 1900-1915  __**

__ Born __ : 1868 A.C. __ Died __ : 1953 A.C. __ Birth Place __ : Morrison, Illinois __ Discovery __ : In 1909 Millikan began a series of experiments to determine the electric charge carried by a single electron. He began by measuring the course of charged water droplets in an electrical field. The results suggested that the charge on the droplets is a multiple of the elementary electric charge, but the experiment was not accurate enough to be convincing. He obtained more precise results in 1910 with his famous oil-drop experiment in which he replaced water (which tended to evaporate too quickly) with oil. Shortly after the experiment's publication in 1910, Millikan was rewarded with a full professorship. The apparatus associated with Millikan's oil-drop experiment is shown in the figure (//left//). A closed chamber with transparent sides is fitted with two parallel metal plates, which acquire a positive or negative charge when an electric current is applied. At the start of the experiment, an atomizer sprays a fine mist of oil droplets into the upper portion of the chamber. Under the influence of gravity and air resistance, some of the oil droplets fall through a small hole cut in the top metal plate. When the space between the metal plates is ionized by radiation (e.g., X rays), electrons from the air attach themselves to the falling oil droplets, causing them to acquire a negative charge. A light source, set at right angles to a viewing microscope, illuminates the oil droplets and makes them appear as bright stars while they fall. __ Biography __ : Son of a Congregational minister from Morrison, Illinois, Millikan was educated at Oberlin, where he studied classics, and Columbia University, where he obtained his PhD in 1895. After a year in Europe, studying under Max Planck and Walther Nernst, he took up an appointment in 1896 at the University of Chicago, being promoted to a full professorship in 1910. Millikan moved to the California Institute of Technology in 1921 as director of the Norman Bridge Laboratory, a position he held until his retirement in 1945.
 * Robert Millikan** [[image:http://www-news.uchicago.edu/releases/06/images/061128.millikan.jpg width="175" height="256" caption="http://www-news.uchicago.edu/releases/06/images/061128.millikan.jpg"]]

Ernest Rutherford ** __ Born __ : 1871 A.C. __ Died __ : 1937 A.C. __ Birth Place __ : Brightwater, New Zealand __ Discovery __ : The discovery of radioactivity: In 1899 Ernest Rutherford studied the absorption of radioactivity by thin sheets of metal foil and found two components: //alpha// (a) radiation, which is absorbed by a few thousandths of a centimeter of metal foil, and //beta// (b) radiation, which can pass through 100 times as much foil before it was absorbed. Shortly thereafter, a third form of radiation, named //gamma// (g) rays, was discovered that can penetrate as much as several centimeters of lead. The three kinds of radiation also differ in the way they are affected by electric and magnetic fields. In 1911, Rutherford cooked up a new model of the atom in which all of the positive charge is crammed inside a tiny, massive nucleus about ten thousand times smaller than the atom as a whole. That's equivalent to a marble in the middle of a football stadium. The much lighter electrons, he assumed, lay well outside the nucleus. To the shock and amazement of everyone, the atoms of which planets, people, pianos, and everything else are made consisted almost entirely of empty space. Rutherford's nuclear model of the atom was a huge step forward in understanding nature at the ultra small scale. But even as it closed the casebook on the alpha particle experiment, it threw open another one. Since the nucleus and its retinue of electrons are oppositely charged, and therefore attract one another, there didn't seem anything to stop the electrons from being pulled immediately into the nucleus. Throughout the universe, atomic matter ought to implode in the wink of an eye. Rutherford countered by saying that the atom was like a miniature solar system: the electrons circled the nucleus in wide orbits just as planets orbit the sun. This is the picture of atoms that most of us still carry around in our heads. It's an appealing, easy-to-grasp image – one that's inspired many a logo of the atomic age. Yet theorists were well aware of its shortcomings right from the start. __ Biography __ : Ernest Rutherford was the brilliant New Zealand physicist who explained natural radioactivity, determined the structure of the atom, and changed one element into another (nitrogen to oxygen) by splitting an atom's nucleus. A farm boy from New Zealand's South Island, he spent most of his professional career overseas at McGill University in Montreal, Canada (1895-98), and at Manchester University (1898-1907) and Cambridge University (1919-37) in the United Kingdom. Rutherford was an energetic pioneer in nuclear physics: he discovered (and named) alpha and beta radiation, named the nucleus and proton and won the 1908 Nobel prize in chemistry for explaining radioactivity as the disintegration of atoms. Rutherford's description of an atomic structure with orbital electrons became the accepted model (with further help provided by his student and colleague, Niels Bohr), and in 1920 he predicted the existence of the neutron, which was later discovered by James Chadwick. Rutherford was knighted in 1914, served as president of the Royal Society from 1925-30, and in 1931 was named Ernest, Lord Rutherford of Nelson (New Zealand).
 * [[image:http://rds.yahoo.com/_ylt=A0WTb_mDnhRJGjUAYPyjzbkF/SIG=12uboqp8l/EXP=1226174467/**http%3A//nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford.jpg]]

Charles Glover Barkla** http://nobelprize.org/nobel_prizes/physics/laureates/1917/barkla-bio.html.
 * [[image:http://content.answers.com/main/content/wp/en-commons/thumb/8/8b/200px-Charles_Glover_Barkla.jpg]]
 * DOB-DOD:** 7 June 1877-23 October 1944
 * Birthplace:** Widnes, Lancashire, England
 * Discovery:** His discovery of homogeneous radiations characteristic of the elements showed that these elements had their characteristic line spectra in X-ray and he was the first to show that secondary emission is of two kinds, one consisting of X-rays scattered unchanged, and the other a fluorescent radiation peculiar to the particular substance. He discovered the polarisation of X-rays, an experimental result of considerable importance for it meant that X-radiation could be regarded as similar to ordinary light. Barkla made valuable contributions to present knowledge on the absorption and photographic action of X-rays and his later work demonstrated the relation between the characteristic X-radiation and the corpuscular radiation accompanying it.
 * Life of Charles Barkla:** His father, J.M. Barkla, was Secretary to the Atlas Chemical Company. He was educated at the Liverpool Institute and entered University College, Liverpool, in 1894 to study mathematics and physics, the latter under Oliver Lodge. He graduated with First Class Honors in Physics in 1898 and in the following year he obtained his master's degree. Also in 1899, he was awarded a research scholarship by the Royal Commissioners for the Exhibition of 1851 and he proceeded to Trinity College, Cambridge, to work in the Cavendish Laboratory with [|J. J. Thomson] . In 1913, Barkla accepted the Chair in Natural Philosophy in the University of Edinburgh and he held this position until his death. Charles Glover Barkla married Mary Esther, the eldest daughter of John T. Cowell of Douglas, Receiver-General of the Isle of Man, in 1907. They had two sons and one daughter. Their youngest son, Flight Lieutenant Michael Barkla, a brilliant scholar, was killed in action in 1943. Barkla's chief recreation was singing - he had a powerful baritone voice and he was a member of the King's College Chapel Choir, 1901-1902. Latterly, he had also become fond of golf.

**Werner Heisenberg** __ Born __ : 1901 A.C. __ Died __ : 1976 A.C. __ Birth Place __ : Würzburg, Germany "The more precisely the position is determined, the less precisely the momentum is known" __ Discovery __ : He is best known as a founder in Quantum Mechanics, the new physics of the atomic world, and especially for the uncertainty principle in quantum theory. He is also known for his controversial role as a leader of Germany's nuclear fission research during World War II. After the war he was active in elementary particle physics and West German science policy. This is a succinct statement of the "uncertainty relation" between the position and the momentum (mass times velocity) 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.
 * __ 1915-1950  __**

__ Biography __ : Heisenberg, with mathematical help from Max Born, developed in 1925 the first version of Quantum mechanics, a matrix method of calculating the behavior of electrons and other subatomic particles. The method was superseded as a practical tool soon after by the more inuitive wave equation of Erwin Schrödinger, but matrix mechanics remains a great intellectual accomplishment. Heisenberg's most lasting contribution was his discovery in 1927 of the uncertainty principle, a foundation of quantum theory. A few years later he introduced a new quantum number called isotopic spin. Heisenberg continued to contribute to particle physics, introducing useful computational techniques in the 1950s.

Erwin Schrodinger ** __ Born __ : 1887 A.C. __ Died __ : 1961 A.C. __ Birth Place __ : Erdberg, Vienna, Austria-Hungary __ Discovery __ : Erwin Schrodinger was one of the main architects of quantum mechanics. Schrodinger developed the wave mechanics. It became the second formulation of quantum mechanics. The first formulation, called matrix mechanics, was developed by Werner Heisenberg. Schrodinger’s wave equation (or Schrodinger equation) is one of the most basic equations of quantum mechanics. It bears the same relation to the mechanics of the atom as Newton’s equations of motions bear to planetary astronomy. However, unlike Newton’s equations, which result definite and readily visualized sequence of events of the planetary orbits, the solutions to Schrodinger’s wave equation are wave functions that can only be related to probable occurrence of physical events. Schrodinger’s wave equation is a mathematically sound atomic theory. It is regarded by many as the single most important contribution to theoretical physics in the twentieth century. Schrodinger’s book, “What is Life?” led to progress in biology.
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__ Biography __ : The Austrian theoretical physicist Erwin Schrodinger, b. Aug. 12, 1887, d. Jan. 4, 1961, published (1926) 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. He succeeded (1927) Max Planck in the chair of theoretical physics at the University of Berlin but left Germany in 1933 because of Nazi threats--the same year he shared the Nobel Prize for physics with Paul Dirac for his contributions to atomic theory. 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. He also worked on problems of general relativity and cosmology and on a unified field theory. Late in his life Schrodinger studied the foundations of physics and their implications for philosophy.


 * Niels Henrik David Bohr**
 * DOB-DOD:** 7 October 1885 –18 November 1962
 * Place of origin:** Copenhagen, Denmark

http://en.wikipedia.org/wiki/Niels_Bohr. http://www.helium.com/items/213494-niels-bohr-and-his-discovery-of-the-atomic-structure. http://library.thinkquest.org/15567/bio/bohr.html
 * Life of Niels Bohr:** The Danish physicist Niels Henrik David Bohr, b. Oct. 7, 1885, d. Nov. 18, 1962, 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. There he worked under Ernest Rutherford.
 * Discovery:** Bohr discovered that Ernest Rutherford's idea of the structure of an atom had a few problems. Bohr acknowledged that electrons existed at set levels of energy, that is, at fixed distances from the nucleus. As long as electrons stay in these energy levels they are stable. Electrons give or take energy only when they change their energy levels. 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. Though electrons make small changes in energy, an electron which is not in its native energy level always has to fall back to its original, stable level.


 * James Chadwick**
 * DOB-DOD:** 20 October 1891-24 July 1974
 * Place of Origin** Cheshire, England


 * Life of James Chadwick:** Son of John Joseph Chadwick and Anne Mary Knowles. He attended Manchester High School prior to entering Manchester University in 1908; he graduated from the Honours School of Physics in 1911 and spent the next two years under Professor (later lord) Rutherford in the Physical Laboratory in Manchester, where he worked on various radioactivity problems, gaining his M.Sc. degree in 1913. That same year he was awarded the 1851 Exhibition Scholarship and proceeded to Berlin to work in the Physikalisch Technische Reichsanstalt at Charlottenburg under Professor H. Geiger.During World War I, he was interned in the Zivilgefangenenlager, Ruhleben. After the war, in 1919, he returned to England to accept the Wollaston Studentship at Gonville and Caius College, Cambridge, and to resume work under Rutherford, who in the meantime had moved to the Cavendish Laboratory, Cambridge.


 * Discovery:** 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.

Works Citied: [|http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec05.html] [|www.humanistictexts.org] http://www.aip.org/history/curie/brief/02_love/love_1.html http://www.aip.org/history/heisenberg/p01.htm http://www.answers.com/topic/robert-millikan http://www.aip.org/history/electron/jjthomson.htm. http://en.wikipedia.org/wiki/Thomson_model. http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html http://www.iep.utm.edu/t/thales.htm http://en.wikipedia.org/wiki/Thales_of_Miletus#Theory http://www.utm.edu/research/iep/a/aristotl.htm#H1 http://www.corrosion-doctors.org/Periodic/Periodic-Mendeleev-Principles-of-Chemistry.htm http://www.answers.com/topic/george-johnstone-stoney http://en.wikipedia.org/wiki/George_Johnstone_Stoney


 * Electron Cloud Model**

This intuitive model provides a simplified way of visualizing an electron as a solution of the [|Schrödinger equation], an advancement using the [|scientific method] to surprising observations that could only be explained by introducing randomness. It is also often referred to as an orbital, because the two terms similarly conceptualize the space where an electron is likely to be found but cannot be actually pinpointed. In the electron cloud analogy, the [|probability density] of an electron, or [|wavefunction], is described as a small cloud moving around the [|atomic] or [|molecular nucleus], with the opacity of the cloud proportional to the probability density. The model evolved from the earlier [|Bohr model], which likened an electron [|orbiting] an atomic nucleus to a planet orbiting the sun. The electron cloud formulation better describes many observed phenomena, including the [|double slit experiment], the [|periodic table] and [|chemical bonding], and atomic interactions with light. Although lacking in certain details, the intuitive model roughly predicts the experimentally observed [|wave-particle duality], in that electron behavior is described as a delocalized wavelike object, yet compact enough to be considered a particle on certain length-scales.



**Plum Pudding Model**

In Thomson’s "Plum Pudding Model" each atom was a sphere filled with a positively charged fluid. The fluid was called the "pudding." Scattered in this fluid were electrons known as the "plums." The radius of the model was 10-10 meters. Thomson suggested that the positive fluid held the negative charges, the electrons, in the atom because of electrical forces. However, this was only a very vague explanation and failed to provide any definite answers. This model was later proved incorrect when [|Ernest Rutherford] showed that the positive charge is concentrated in the nucleus. http://library.thinkquest.org/28582/history/plum.htm. http://en.wikipedia.org/wiki/J._J._Thomson.

Each orbit around the nucleus represents an energy level, and electrons cannot exist in between orbits. Orbits closer to the nucleus have lower energy. If energy is added, an electron can be "excited" to jump to a higher energy level--an orbit farther from the nucleus. Eventually, though, the electron will return to its original state, and the atom will give off energy equal to the difference between the two orbits.In some materials, the energy is given off as X-rays; other materials produce specific colors of visible light, or other types of electromagnetic energy.Each orbit can hold only a certain number of electrons. The lower-energy orbits must fill up first, if the atom is to be at its "ground" state. This is the lowest energy state and therefore most stable state.With more research, scientists discovered that atomic structure is more complex, and that the Rutherford-Bohr model contained serious flaws. http://www.epa.gov/rpdweb00/understand/rutherford.html.
 * Rutherford-Bohr Model**

The Bohr Model is probably familiar as the "planetary model" of the atom illustrated in the adjacent figure that, for example, is used as a symbol for atomic energy. In the Bohr Model the neutrons and protons occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the Sun. This similarity between a planetary model and the Bohr Model of the atom ultimately arises because the attractive gravitational force in a solar system and the attractive Coulomb (electrical) force between the positively charged nucleus and the negatively charged electrons in an atom are mathematically of the same form. http://csep10.phys.utk.edu/astr162/lect/light/bohr.html.
 * Planetary Model**