Carbon dating and half life calculations
Outside the range of recorded history, calibration of the 14 clock is not possible.
This means the above calculations are only evolution speculation and NOT backed up by real science.
Some radioisotopes have very long half-lives, some have very short half-lives.
The 6 proton 6 neutron atoms are said to have a mass of 12 and are referred to as "carbon-12." The nuclei of the remaining one percent of carbon atoms contain not six but either seven or eight neutrons in addition to the standard six protons.The half-life of some radioisotopes is given in the table below: years.This means that if a rock contained 100 g of uranium-238 at the time the earth came into being, then at the present time the rock would contain only half that amount, ½ × 100 = 50 g, of uranium-238.If you wait another 4.5 × 10 years and measure the mass of uranium-238 in that rock you will find there will be only ½ × 50 = 25 g left.We could tabulate the mass of uranium-238 remaining after an interval of time measured in numbers of half-lives as shown below: years, we can read it straight of the graph as a mass of approximately 21.5 grams.