Radioactive decay allows geologists and physicists to measure the age of ancient fossils, rocks and even the Earth.This process is called radiometric or radioactive dating.Two situations where we can do this involve Potassium-40 atoms and Carbon-14 atoms.All radioactive atoms decay to become a more stable kind of atom.Carbon dating is used to determine the age of biological artifacts up to 50,000 years old.This technique is widely used on recent artifacts, but educators and students alike should note that this technique will not work on older fossils (like those of the dinosaurs alleged to be millions of years old).Some of the different kinds of radioactive atoms used to date objects are shown in the following table: Potassium-Argon Dating Potassium atoms are used to date rocks that have formed from molten rock. Argon is an inert gasit does not chemically bond to other atoms.
The best estimate from this dating technique says the man lived between 33 BC. From the ratio, the time since the formation of the rock can be calculated.The original radioactive atom is known as a parent isotope, while the atom produced by the decay process is known as a daughter isotope. For example Uranium-235 and Uranium-238 are both Uranium atoms with the same number of protons, but they have a different number of neutrons.The number used to identify the isotope refers to the total number of particles in the nucleus of each atom.The boat of a pharaoh was discovered in a sealed crypt and reassembled in a museum near the pyramids (see Fig. The age of our galaxy and earth also can be estimated using radioactive dating.Using the decays of uranium and thorium, our galaxy has been found to be between 10 and 20 billion years old and the earth has been found to be 4.6 billion years old. Within experimental error, this estimate agrees with the 15 billion year estimate of the age of the Universe.Though still heavily used, relative dating is now augmented by several modern dating techniques.