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Applied Mathematics · Ch 5 — Differential Equations and Modeling

Carbon Dating

5.12.6

Carbon Dating

Carbon dating is a technique used to estimate the age of the remains of plants and animals. Living organisms continuously exchange carbon with their environment, which keeps the proportion of radioactive carbon-14 in their tissue roughly constant; once the organism dies, this exchange stops and the carbon-14 already present simply decays away. Comparing the amount of carbon-14 remaining in a sample against the amount found in living matter lets scientists estimate how long ago the organism died.

Carbon-14 decays exponentially, following the growth-and-decay model with a negative rate constant. Its decay is usually described through its half-life — the time taken for a given amount to reduce to half its original value — which for carbon-14 is approximately 57005700 years. If m(t)m(t) is the mass of carbon-14 present after tt years and m0m_0 is the mass at t=0t = 0,

m(t)=m0 ekt,k<0m(t) = m_0\, e^{kt}, \quad k < 0 …