Potassium argon radiometric dating
Willard Libby invented the carbon dating technique in the early 1950's.
The amount of carbon 14 in the atmosphere today (about .0000765%), is assumed there would be the same amount found in living plants or animals since the plants breath CO2 and animals eat plants. Since sunlight causes the formation of C-14 in the atmosphere, and normal radioactive decay takes it out, there must be a point where the formation rate and the decay rate equalizes. Let me illustrate: If you were trying to fill a barrel with water but there were holes drilled up the side of the barrel, as you filled the barrel it would begin leaking out the holes.
This is why most people say carbon dating is only good for objects less than 40,000 years old.
Nothing on earth carbon dates in the millions of years, because the scope of carbon dating only extends a few thousand years.
The carbon in the atmosphere normally combines with oxygen to make carbon dioxide (CO2).
They do not know that the amount of carbon-14 in the atmosphere is constant. In addition to the above assumptions, dating methods are all subject to the geologic column date to verify their accuracy.
Present testing shows the amount of C-14 in the atmosphere has been increasing since it was first measured in the 1950's. Etna, Sicily (AD 1972) gave K-AR age of 350,000 years old. If a date obtained by radiometric dating does not match the assumed age from the geologic column the radiometric date will be rejected. 30 "The lower leg of the Fairbanks Creek mammoth had a radiocarbon age of 15,380 RCY, while its skin and flesh were 21,300 RCY. 124 The two Colorado Creek mammoths had radiocarbon ages of 22,850 670 and 16,150 230 years respectively." --In the Beginning Walt Brown p.
Plants breathe CO2 and make it part of their tissue.
Animals eat the plants and make it part of their tissues.
Whenever the worldview of evolution is questioned, this topic always comes up.