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October 7.docx

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Department
Earth Sciences
Course
ESS102H1
Professor
C.Banks
Semester
Fall

Description
October 7 Earth’s Absolute Age Reconciling Geology and Physics - at the end f the 19 century there were two camps with contrary opinions: o geologists: Earth is at least 100 million years old (observations and simple calculations) o physicists: Earth cannt be older than 20 million years (simple evidence and complex calculations) - (A) one or more of the researchers is incompetent; or - (B) an “anomaly” in Kuhn’s sense, has been identified – one which could lead to a significant revolution in the science - In 1899, T. C. Chamberlin (1843-1928), Professor of Geology at the University of Chicago and founder of the “Journal of Geology” suggested that the confidence of the physics was unwarranted: o “Is present knowledge relevant to the behaviour of matter under such extraordinary conditions as obtained in the interior of the sun sufficiently exhaustive to warrant the assertion that no unrecognized sources of heat reside there?” - Aside: he suggested that planets formed by accretion 1. Radioactivity o William Conrad Roentgen (1845-1923)  Professor at Wuerzberg and then Munich, Germany  discovered X-rays on 08 Nov 1895  won first Physics Nobel Prize in 1901  he enjoyed doing science • donated money to his university • rejected title “von Roentgen” • refused to take out patents so world could benefit  discovery of “a new type of rays” which traveled through paper, wood and aluminum (when asked about his thoughts at the moment of discovery he replied: “I didn’t think, I investigated.”)  “A piece of sheet aluminum, 15 mm thick, still allowed the X-rays (as I will call the rays, for the sake of brevity) to pass, but greatly reduced the fluorescence.”  original paper he read before the Wuerzberg Physical and Medical Society in 1895 o Antoine Henri Becquerel (1852-1908)  discovered natural X-rays  was looking for glowing among naturally florescent minerals  had exposed a uranium salt to sunlight and placed on photographic plates wrapped in black paper  photographic plates revealed image of uranium crystals, Becquerel believbed that the sun’s energy was absorbed by the uranium which then emitted X-rays  shared 1903 Nobel prize with Marie and Pierre Curie o Marie and Pierre Curie  in 1903 Pierre discovered that radium gives off heat naturally  it continued to do so indefinitely, at least in comparison with the behaviour of most materials emitting heat (such as a hot iron or a burning lump of coal)  aside: Pierre research about magnetism and temperature in his doctoral thesis  Marie discovered that the strength of the radiation did not depend on the compound, but the amount of uranium they contained. She concluded that it must be linked to the interior of the atom itself. After thousands of crystallizations, Marie isolated one decigram of almost pure radium chloride and determined radium’s atomic weight as 225  She received a second Nobel prize in chemistry and died of anemia (likely caused by radiation exposure)  implications of the Curie discovery: 1. Power generation: materials can contain sources of energy far in excess of the known chemical energy 2. Calculations which ignored this were in
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