There are various ways of determining the age of materials. These include traditional methods such as radioactive carbon dating, k-ar, rubidium-strontium, tritium, uranium-thorium, ionium-thorium, fission-track, and common-lead dating, and most recently spin resonance and thermoluminescence.
Radioactive carbon dating is a well-known method of determining the age of biological organisms, including woods, seeds, and bones.
In all living systems, carbon is absorbed from the atmosphere, and will remain in the system for 70 or 80 thousand years.
By measuring the rate, or half-life, at which a carbon atom decays in an organic system, the age of the organism may be accurately determined.
Half-life is the time required for a radioactive atom to decay to one-half of its original mass. The time when an individual nucleus will decay is impossible to predict, but the decay rate, or half-life, of a large number of nuclei is a precise mathematical quantity. Half-lives range from millionths of a second to 10 billion years.
The oldest living plant on Earth, known as King’s Holly, was discovered in 1934 in a rain forest in Tasmania. This wide-spread, low-growing shrub, the only known example of its species, is over 43 thousand years old, based on traditional carbon dating.
Other traditional methods of radiometric dating can determine the geological time scale, the age of provinces within continents, the chronology of the Earth’s magnetic field reversals, the oldest known terrestrial rocks, the age of sediment deposits, temperature history, the rate of movement of water masses, and the formation of continental crust.
Both spin resonance and thermoluminescence measure the decay of certain radioactive atoms common in many rocks, which acts as an atomic clock for minerals in the rocks. These recent dating techniques are more accurate than earlier methods, and can extend farther back in time.