Method of carbon 14 dating
Cosmic rays enter the earth's atmosphere in large numbers every day.
For example, every person is hit by about half a million cosmic rays every hour.
It must be noted that radiocarbon dating is only applicable to materials that were once part of a living organism.
Any carbon-containing material that affects the carbon 14 content of any given sample is therefore a contaminant.In general, infinite-age contamination can make a sample considerably older while modern contamination can make the sample significantly younger than its true age.Regardless of the carbon dating methodology employed, be it radiometric dating or the accelerator mass spectrometry (AMS) method, a process must be done before analysis to get rid of all possible contaminants. Radiocarbon dating labs receive various materials for analysis but not all portions of the samples can be used.Limestone is of geological origin and would be much older than any archaeological sample; hence, inclusion of limestone during the carbon 14 dating would make the sample older than its true age.Humic and fulvic acids are naturally present in soil where microbial degradation of plants and animals has occurred.