Explanation: Carbon dating is used to determine age by actually using a carbon radioactive isotope, which is carbon-14. This radioactive isotope of carbon, unlike other forms in which carbon can be found, decays at a constant rate, and this crucial characteristic of this isotope for age dating. Specifically, organisms, while alive, absorb a certain amount of this isotope from the atmosphere. Measuring the amount of this radioactive isotope and its relation to non-radioactive carbon in fossil remains, gives the age of the organisms, because, as mentioned, this radioactive isotope decays at a uniform rate.