So, we have a “clock” which starts ticking the moment something dies.
Obviously, this works only for things which were once living.
To derive ages from such measurements, unprovable assumptions have to be made such as: There is plenty of evidence that the radioisotope dating systems are not the infallible techniques many think, and that they are not measuring millions of years. For example, deeper rocks often tend to give older “ages.” Creationists agree that the deeper rocks are generally older, but not by millions of years.
Geologist John Woodmorappe, in his devastating critique of radioactive dating, points out that there are other large-scale trends in the rocks that have nothing to do with radioactive decay.
We will deal with carbon dating first and then with the other dating methods.
Carbon has unique properties that are essential for life on Earth.
Overall, the energy of the Earth's magnetic field has been decreasing, so more C is being produced now than in the past.