Radioactive Decay Acts Like Nature Clock

Knowing a rock age sounds impossible at first. But random nuclear behavior becomes a reliable clock over long spans. In radioactive decay, nuclei transform into other elements. Half life is the time for half of a sample to decay, and each isotope has its own value. Scientists measure parent and daughter isotope ratios to estimate age. The method spans geology and human history. Nature produces materials with clocks inside. You can read time not only with calendars, but with atoms.