Radioactive dating isotopes
Thyroid tissue that may be cancerous and has left the throat region can be located in the body with radioactive iodine.
Radioactive isotopes are often used in scientific and medical fields.
Please see the link provided on how the age of a fossil is determined.
For carbon dating, the isotope used is Carbon-14, which has a half life of 5,700 years.
Learn about different types of radiometric dating, such as carbon dating.
Igneous intrusions found cutting through, or above or below the strata containing the fossil is used to narrow down its age. Elemental atoms all have the same number of protons (and therefore also electrons); but they might vary in the number of neutrons.
These variations are called isotopes of an element.