How Do You Know the Age of Fossils and Other Old Things?

Description: Radiometric dating is based on the phenomenon of radioactivity. Counting the number of radioactive atoms in an object can often tell you its age, in the thousands, millions, or even billions of years. Atoms of radioactive elements, such as uranium, have so much energy that their cores, or nuclei, are literally flying apart, shedding motes of their matter in a process called decay. Through our observations and understanding of physics, we know that each radioactive element decays at its own steady rate. By revealing the ages of things, radiometric dating has made it a lot easier to read the history written in the rocks and artifacts buried in the Earth, giving us a sense of the vast time that it took for our planet to take shape and for life and eventually us to evolve. We can only wonder at what it will reveal about the past next.