What is the primary method of absolute dating?

The primary method of absolute dating is radioactive dating. This technique uses the decay of radioactive isotopes present in rocks and organic materials to determine their age in years. Each radioactive isotope has a known half-life, the time it takes for half of a given sample to decay. By measuring the remaining amount of the isotope within a sample and knowing the half-life, scientists can effectively calculate the age of the sample. This method provides a specific age range, allowing for precise dating of geologic events, fossils, and archaeological artifacts.

In contrast, comparing fossils to one another relies on relative dating techniques, which can only determine the sequence of events without providing an exact age. Estimating based on sediment layers also falls under relative dating, as it looks at the order of rock layers but does not quantify exact ages. Assessing physical characteristics may help in identifying species or formations, but it does not provide a timeline. Therefore, radioactive dating stands out as the most reliable method for determining the absolute age of geological and biological specimens.