What is a dating method used to estimate Ages after something dies?

Answer 1

For things that were once living the best method is what is called Carbon Dating, which is based on the decay of carbon-14. As long as the thing remains alive it is in equilibrium with the environment and maintains a constant level of carbon-14 in its tissues. On death this equilibrium is broken and the remaining carbon-14 slowly decays away without anymore replacing it from the environment. The age can be calculated by measuring how much carbon-14 has been lost from the equilibrium level.

The problems with Carbon Dating is that it does not work for things that died more than 40,000 years ago due to the fact that the halflife of carbon-14 is 5570 years so after 40,000 years there isn't enough left to measure, and the environmental level of carbon-14 does change some over time so known reference sources (e.g. tree rings) must be used for recalibration of Carbon Dating results.

Beyond 40,000 years other radiometric dating methods must be used, but unlike Carbon Dating they cannot determine age from death.

Answer 2

It depends on how old the dead thing is, but for anything over 5000 years old, radioactive decay rates are probably the best methods.