When scientists first began to compare carbon dating data to data from tree rings, they found carbon dating provided "too-young" estimates of artifact age.
Scientists now realize that production of carbon-14 has not been constant over the years, but has changed as the radiation from the sun has fluctuated.
Levels of carbon-14 become difficult to measure and compare after about 50,000 years (between 8 and 9 half lives; where 1% of the original carbon-14 would remain undecayed).
The various confounding factors that can adversely affect the accuracy of carbon-14 dating methods are evident in many of the other radioisotope dating methods.
Although the half-life of some of them are more consistent with the evolutionary worldview of millions to billions of years, the assumptions used in radiometric dating put the results of all radiometric dating methods in doubt. Although the half-life of carbon-14 makes it unreliable for dating fossils over about 50,000 years old, there are other isotopes scientists use to date older artifacts.
Carbon-14 cannot be used to date biological artifacts of organisms that did not get their carbon dioxide from the air.
This rules out carbon dating for most aquatic organisms, because they often obtain at least some of their carbon from dissolved carbonate rock.
Any radiometric dates that show a supposedly “old” rock to be young are rejected “Few people realize that the index fossil dating system, despite its poor assumptions and many problems, is actually the primary dating tool for geologic time. In other words, radiometric dating methods are actually fit into the geological column, which was set up by [index] fossil dating over 100 years ago.”(Michael Oard, meteorologist and creationist scientist, 1984) All radiometric dating methods use this basic principle to extrapolate the age of artifacts being tested.
These long time periods are computed by measuring the ratio of daughter to parent substance in a rock, and inferring an age based on this ratio.
The mathematical premise undergirding the use of these elements in radiometric dating contains the similar confounding factors that we find in carbon-14 dating method.
Most scientists today believe that life has existed on the earth for billions of years.
These isotopes have longer half-lives and so are found in greater abundance in older fossils.