Carbon dating practice questions
'' But at earlier times, the carbon dates were substantially younger than the dates we estimated by uranium-thorium analysis,'' he said.'' The largest deviation, 3,500 years, was obtained for samples that are about 20,000 years old.'' One reason the group believes the uranium-thorium estimates to be more accurate than carbon dating is that they produce better matches between known changes in the Earth's orbit and changes in global glaciation. Fairbanks, a member of the Lamont-Doherty group, said that if the dates of glaciation were determined using the uranium-thorium method, the delay - and the puzzle - disappeared.Divide the percentage in half again 12.5% left three half lives have passed.Again divide it in half 6.25% and four half lives have passed.
Y., reported today in the British journal Nature that some estimates of age based on carbon analyses were wrong by as much as 3,500 years.Uranium 234, a radioactive element present in the environment, slowly decays to form thorium 230.Using a mass spectrometer, an instrument that accelerates streams of atoms and uses magnets to sort them out according to mass and electric charge, the group has learned to measure the ratio of uranium to thorium very precisely.In principle, any material of plant or animal origin, including textiles, wood, bones and leather, can be dated by its content of carbon 14, a radioactive form of carbon in the environment that is incorporated by all living things.Because it is radioactive, carbon 14 steadily decays into other substances.