Radiometric Dating
The general technique of determining the age of a sample from the decay of a radioactive nuclide it contains.
Formula / equation
t = (1/λ) ln(1 + D/P)
Unit
years
In depth
The method assumes a closed system with a known initial composition and a constant decay rate. Choosing an isotope whose half-life is comparable to the age being measured gives the best precision, and cross-checking with a second isotope tests the assumptions.
Examples in the real world
Potassium–argon dating of volcanic ash layers containing hominin fossils; rubidium–strontium dating of ancient crust.