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A Sense of Time<br />Three Rivers Science SymposiumUniversity of Saint FrancisSister Carol Meyers <br />

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How old?<br />Time has been measured in manyways: Lunarcalendars, Julian calendars, Gregoriancalendars, etc. <br />Tree rings canbeused to tell the age of a tree<br />Radioactivitycanbeused to tell the age of rocks, icecores, etc. <br />Click on picture to hear how we tell the age of things<br />

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Geological Time Scale (in millions of years) <br />The Holocene (the latest epoch) is too short to be shown clearly on this timeline<br />

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To obtain the content ratio of isotopes 40Ar to 39K in a rock or mineral, the amount of Ar is measured by mass spectrometry of the gases released when a rock sample is melted in flame photometry or atomic absorption spectroscopy.<br />The isotopic composition of oxygen atoms in the Earth's atmosphere is 99.759% 16O, 0.037% 17O and 0.204% 18O.[10] Because water molecules containing the lighter isotope are slightly more likely to evaporate and fall as precipitation,[11] fresh water and polar ice on earth contains slightly less (0.1981%) of the heavy isotope 18O than air (0.204%) or seawater containing (0.1995%). This disparity allows analysis of temperature patterns via historic ice cores<br />Isotope ratios <br />

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RadiocarbonDating<br /><ul><li>14C is produced in a steady amount in the atmosphere when 14N is struck by a neutron. The Nucleus emits a positron which turns a proton into a neutron

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As long as a substance is living its interchange of CO2 keeps the amount of 14C constant.

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At death the 14C decays by emitting a beta particle to become 14N.

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14C decays with a half-life of 5,730 years</li></ul>Click on picture for video<br />

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The Structure claimed to be the Noah's Ark in Durupınar site, Agri, Turkey<br />Noah’s Ark would be around 2900 BC making it 4910 years old today <br />

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Tutankhamun ruled Egypt between 1334 and 1325 BC. He was probably the 12th ruler of Egypt's 18th Dynasty.<br /> <br />

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The fossil was dated reliably in 1990–1992 by applying the argon-argon radiometric dating method to the volcanic ash surrounding Lucy. Initial attempts were made in 1973 and 1974 to estimate the age of the fossil using the potassium-argon radiometric dating method. Found to be 3.22 and 3.18 million years . <br />Lucy’s skeleton reconstructed<br />Cleveland Museum of Natural History <br />Louis and Mary Leakey made Olduvai Gorge, located within what is now the famous Serengeti Park in Tanzania, their domain.<br />

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5,300-year-old mummy known as Otzi was found in 1991Bone studies (from nine different samples) suggest that, when he died, the Iceman was 45.7 years of age<br />

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Click on picture to see Sherlock Holmes<br />