Scientific controversy with radioisotopic dating

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Some isotopes are unstable, and over time these isotopes “decay” into isotopes of other elements.For example, Potassium-40 is unstable and decays into Argon-40.As time passes, a rock will have more and more Argon-40 and less and less Potassium-40.Radiometric dating is possible because this decay occurs at a known rate, called the “half-life” of the radioactive element.The oldest reliably dated rock formation is in Greenland, where several different isotopes were used to find an age of 3.6 billion years.To find older rocks that haven’t been eroded, we need to look beyond Earth.

Each year, snowfall varies throughout the seasons and an annual layer is formed.If you’ve ever seen a horizontal slice of a tree trunk, you’ve seen how a tree forms a new growth ring each year.In years of drought, the tree grows less quickly so the ring is narrower; in good growing seasons the ring is thicker.Meteorites are rocks from the solar system that have fallen to Earth recently and haven’t suffered much erosion.Their pristine interiors give an age that dates back to their formation at the beginning of the solar system.

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