Radiometric dating age of the earth who is diggy simmons dating now
Scientists discovered that rocks could be timepieces -- literally.
Many chemical elements in rock exist in a number of slightly different forms, known as isotopes.
Certain isotopes are unstable and undergo a process of radioactive decay, slowly and steadily transforming, molecule by molecule, into a different isotope.
This rate of decay is constant for a given isotope, and the time it takes for one-half of a particular isotope to decay is its radioactive half-life.
Using this technique, called radiometric dating, scientists are able to "see" back in time.
Segment from A Science Odyssey: "Origins."Geologists have calculated the age of Earth at 4.6 billion years.
At time 1, 50% of the parent atoms remain; at time 2, only 25% remain, and so on.
Radiometric dating works best on igneous rocks, which are formed from the cooling of molten rock, or magma.
As magma cools, radioactive parent isotopes are separated from previously formed daughter isotopes by the crystallization process.
Ideally, the mineral crystals in igneous rocks form a closed system--nothing leaves or enters the crystal once it is formed.
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.