The basic principle behind radiometric dating is the use of the decay rates of radioactive isotopes to determine the age of materials. Every radioactive isotope has a specific half-life, which is the time it takes for half of the isotope to decay into a stable form. By measuring the ratio of parent isotopes to daughter products in a sample, scientists can calculate the time elapsed since the material was formed. This method is crucial for dating fossils, rocks, and understanding geological time scales.