Radioactive dating
The key idea
Radiometric dating uses known radioactive decay laws and isotope ratios to infer elapsed time, provided the relevant system history and initial conditions are adequately constrained.
Why it matters
Different isotope systems suit different materials and timescales; dating is therefore a measurement model, not simply reading an age directly from a sample.
A picture to remember
Different isotope systems suit different materials and timescales; dating is therefore a measurement model, not simply reading an age directly from a sample.