Radiocarbon dating is simply a measure of the level of C isotopes in the atmosphere can vary.
This is why calibration against objects whose age is known is required (14).
The other two isotopes in comparison are more common than carbon-14 in the atmosphere but increase with the burning of fossil fuels making them less reliable for study (2); carbon-14 also increases, but its relative rarity means its increase is negligible. After this point, other Absolute Dating methods may be used.
It also has some applications in geology; its importance in dating organic materials cannot be underestimated enough.
In 1979, Desmond Clark said of the method “we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation” (3).
When the half-life was corrected in 1950, the year was taken as a base date from which to calculate all resulting dates.
Therefore, any expression of “before present” will mean “before 1950”.
The sample passes through several accelerators in order to remove as many atoms as possible until the C pass into the detector.