But for humans whose life span rarely reaches more than 100 years, how can we be so sure of that ancient date? Even the Greeks and Romans realized that layers of sediment in rock signified old age.But it wasn't until the late 1700s -- when Scottish geologist James Hutton, who observed sediments building up on the landscape, set out to show that rocks were time clocks -- that serious scientific interest in geological age began.Geologist Ralph Harvey and historian Mott Greene explain the principles of radiometric dating and its application in determining the age of Earth.
Most atoms are neutral overall, with the number of protons equaling the number of electrons.If there is an unequal number of protons and electrons, the atom has a charge (positive or negative), and it is called an ion. Mass number is the sum of the number of protons plus neutrons.Among the best-known techniques are radiocarbon dating, potassium-argon dating and uranium-lead dating.By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change.and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of the Earth itself, and can also be used to date a wide range of natural and man-made materials.
Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geological time scale.The particles given off during the decay process are part of a profound fundamental change in the nucleus.To compensate for the loss of mass (and energy), the radioactive atom undergoes internal transformation and in most cases simply becomes an atom of a different chemical element.Atomic number of an atom = number of protons in the nucleus of that atom. The mass number may vary for an element, because of a differing number of neutrons. Radioactive decay occurs by releasing particles and energy.Elements with various numbers of neutrons are called isotopes of that element. Note that some elements have both radioactive and non-radioactive isotopes. Radioactive decay occurs by releasing subatomic particles and energy.For a single element, these atoms are called isotopes.