Much of the carbon 14 in the carbon dioxide in the Earth's atmosphere has not degraded much so we can conclude that it was placed there recently.

Question

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Carbon-14 is a radioactive isotope with a half-life of about 5,730 years. If much of the carbon-14 in atmospheric carbon dioxide has not degraded, it suggests that it was introduced relatively recently, as it has not had sufficient time to decay significantly.

Much of the Carbon 14 in the Carbon Dioxide in the Earth's