Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
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.
Thus creationists and others who invoke perceived weaknesses in radiocarbon dating as justification to cast doubt on the great age of the earth are either uniformed on very basic scientific facts, or else are highly being disingenuous to their audience.
Radiocarbon dating has been studied at great length over the past few decades, and its strengths and weaknesses are very well understood at this point in time.
In discussions of the age of the earth and the antiquity of the human race, creationists often assail perceived weaknesses in radiocarbon dating. Morris, for instance, wrote, "Despite its high popularity, [radiocarbon dating] involves a number of doubtful assumptions, some of which are sufficiently serious to make its results for all ages exceeding about 2000 or 3000 years, in serious need of revision." [Morris2000, pg. Radiocarbon dating is based on the fact that the interaction of cosmic rays from outer space with nitrogen atoms in the atmosphere produces an unstable isotope of carbon, namely radiocarbon.But even he “realized that there probably would be variation”, says Christopher Bronk Ramsey, a geochronologist at the University of Oxford, UK, who led the latest work, published today in Science.Various geologic, atmospheric and solar processes can influence atmospheric carbon-14 levels.So, we have a “clock” which starts ticking the moment something dies.Obviously, this works only for things which were once living.