Here are the key assumptions: There is one fact that makes it highly unreasonable to believe that the proportion of C-14 to C-12 was the same in the past as it has been in recent history: It is not in equilibrium.
The rate of C-14 production today is 18% higher than the rate of decay (Whitelaw).
Where t is the age of the fossil (or the date of death) and ln() is the natural logarithm function.
If the fossil has 35% of its carbon 14 still, then we can substitute values into our equation.
When the organism dies, however, it ceases to incorporate carbon into its body.
At this point, and for the years following, the C-14 in the sample begins to decay back into N-14, while the C-12 does not decay.
Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).Anything that dies after the 1940s, when Nuclear bombs, nuclear reactors and open-air nuclear tests started changing things, will be harder to date precisely.Carbon-14 dating is a radiometric dating technique used to deduce the approximate age of organic remains by measuring the quantity of C-14 isotopes in the sample and comparing them with current atmospheric levels.In the case of radiocarbon dating, the half-life of carbon 14 is 5,730 years.This half life is a relatively small number, which means that carbon 14 dating is not particularly helpful for very recent deaths and deaths more than 50,000 years ago.When an organism dies it ceases to replenish carbon in its tissues and the decay of carbon 14 to nitrogen 14 changes the ratio of carbon 12 to carbon 14.