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This Concept Map has information related to: Story Map, These techniques could not date anything older than 200,000 years old. ???? So in 1946 Arthur Holmes was able to announce that the Earth was at least 3 billion yrs old. Although, many felt as if he merely found the age of materials which the Earth had been formed., This discovery led to the removal of lead in gasoline. In addition, his efforts also led to the intro of the Clean Air Act of 1970. ???? Although Patterson was the most influential geologist of the twentieth century, he was never even really mentioned and when he was, his name was misspelled., In spring of 1953, Patterson went to Argonne National Laboratory to use a late-model mass spectrograph. Soon afterward, he had an age for the Earth of 4,550 million yrs old. ???? He then turned his attention to the abundance of lead in the atmosphere., Production workers became ill and at least fifteen died. The company always seemed to hush up the news about all the "mishaps". ???? In 1924, five more workers died and 35 men were permanently damaged., Midgley created a gas that was stable,nonflammable, noncorrosive and safe to breath called CFCs. ???? CFCs went into production in the early 1930s but it took half a century for anyone to realize it was ruining the ozone in the stratosphere., CFCs were just about the worst invention of the twentieth century and were banned in 1974 in the U.S. ???? Willard Libby began the process of radiocarbon dating., Lead was easy to extract and very profitable to produce industrially. Tetraethyl lead also stopped engines from knocking. ???? On Feb. 1, 1923, Ethyl Corp.introduced it for public consumption., He realized that all living things have an isotope of carbon 14. So, by working out how much a sample of carbon had decayed, he was able to get a good age of an object, but only up to a certain point. ???? Radiocarbon dating only worked for objects up to forty thousand years old or so., Patterson's samples were continuously contaminated with large doses of atmospheric lead when exposed to air. ???? He then created the world's first sterile lab. (According to at least one account.), Midgley investigated a compound called tetraethyl lead. ???? Lead could be found in nearly all consumer products.