Accuracy of carbon dating

In 1929, with a beam from Show Low, Arizona, Douglass was able to bridge the gap for the first time ever.Dates were assigned to Southwestern ruins with certainty.Dendrochronology and radiocarbon dating have intertwined histories, she explains, with roots firmly planted at the UA.A 1929 edition of National Geographic boasts, "The Secret Of The Southwest Solved By Talkative Tree Rings." The 35-page article, penned in whimsical prose, was written by Andrew Douglass, the UA scientist who invented tree ring science. In addition to his work as an astronomer at the UA's Steward Observatory, Douglass was the first to discover that tree rings record time.If a Bigtooth Maple were cut down on Mount Lemmon in 2016 and it had 400 rings, you would know the tree started growing in 1616. What if it's been used to build a home or a ship or a bonfire?

"We can use the annual precision of tree rings in combination with carbon-14 to underpin some big questions in terms of the rise and fall of civilizations," says Pearson.

Willard Libby from the University of Chicago put it to the test.

By 1949, he had published a paper in Science showing that he had accurately dated samples with known ages, using radiocarbon dating.

He noticed that trees across the same region, in the same climate, develop rings in the same patterns.

Douglass, with his knack for pattern-recognition, discovered that he could take younger wood with a known date, and then match its rings alongside the pattern of an older sample.

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