Fall.2008.MMA.Thomson.Timeline

Democritus, known in antiquity as the ‘laughing philosopher’ because of his emphasis on the value of ‘cheerfulness,’ was one of the two founders of ancient atomist theory. He elaborated a system originated by his teacher Leucippus into a materialist account of the natural world. The atomists held that there are smallest indivisible bodies from which everything else is composed, and that these move about in an infinite void space. Of the ancient materialist accounts of the natural world which did not rely on some kind of teleology or purpose to account for the apparent order and regularity found in the world, atomism was the most influential. Even its chief critic, Aristotle, praised Democritus for arguing from sound considerations appropriate to natural philosophy. http://plato.stanford.edu/entries/democritus/
 * Democritus**
 * 493-403BC**

Most famous for the his theory of gravity. He also believed that all matter was composed of atoms. http://plato.stanford.edu/entries/newton-philosophy/
 * Isaac Newton**
 * 1642-1727**

John Dalton 1766-1844 Dalton published the atomic theory in 1808 in a book called //A New System of Chemical Philosophy//. 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. http://www.robinsonlibrary.com/science/chemistry/biography/dalton.htm

Wilhelm Roentgen 1845-1923 Wilhelm Roentgen of Germany discoved X-rays. While studying electrical discharge through rarified gas, he found that invisible rays came from the positive electrode and would darken a photographic plate through an opaque wrapping http://www.nuclearfiles.org/menu/timeline/atomic-discovery/discovery.htm

Ernest Rutherford 1871-1937 Ernest Rutherford of New Zealand distinguishede two kinds of rays from radium and its products. Some are stopped by a thin (20 micron) aluminum foil. These he named alpha rays; the more penetrating rays he called beta rays. http://www.nuclearfiles.org/menu/timeline/atomic-discovery/discovery.htm

Marie Curie 1867-1934 Marie Curie of France discovered radium and polonium, the elements that constitute most of the radioactivity in uranium http://www.nuclearfiles.org/menu/timeline/atomic-discovery/discovery.htm

Max Planck 1858-1947 Max Planck of Germany developed quantum theory, which explains matter and energy on the subatomic level. http://www.nuclearfiles.org/menu/timeline/atomic-discovery/discovery.htm

Antoine Henri Bacquerel Antoine Henri Becquerel shared a Nobel Prize in 1903 for Physics with Pierre and Marie Curie for 1898 discovery of natural radioactivity.

Albert Einstein 1879-1955 Albert Einstein published "Fundamental Ideas and Problems of the Theory of Relativity," which addressed convertibility of matter and energy (E=mc2).

Ernest Lawrence 1901-1958
 * Ernest O. Lawrence** of the United States conceived idea for the first cyclotron (atom smasher).