Half of the remaining Carbon-14 then decays over the next 5730 years leaving one fourth of the original amount.
By measuring the ratio of Carbon-14 in a sample and comparing it to the amount in a recently deceased sample its date can be determined.
While there is no proof that the rates were different in the past than they are today, there is also no proof that they were the same.
Thus radioactive dating relies purely on assumptions.
A child mummy is found high in the Andes and the archaeologist says the child lived more than 2,000 years ago.
Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon.
The Carbon-14 within a living organism is continually decaying, but as the organism is continuously absorbing Carbon-14 throughout its life the ratio of Carbon-14 to Carbon-12 atoms in the organism is the same as the ratio in the atmosphere.
Once an organism dies it stops taking in Carbon in any form.
Radiocarbon decays slowly in a living organism, and the amount lost is continually replenished as long as the organism takes in air or food.
Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases.