Carben 14 dating
Libby calculated the half-life of c14 as 5568 ± 30 years.
This means that half of the c14 has decayed by the time an organism has been dead for 5568 years, and half of the remainder has decayed by 11,136 years after death, etc.
This is the clock that permits levels of c14 in organic archaeological, geological, and paleontological samples to be converted into an estimate of time.
The measurement of the rate of radioactive decay is known as its half-life, the time it takes for half of a sample to decay.
During the lifetime of an organism, the amount of c14 in the tissues remains at an equilibrium since the loss (through radioactive decay) is balanced by the gain (through uptake via photosynthesis or consumption of organically fixed carbon).
However, when the organism dies, the amount of c14 declines such that the longer the time since death the lower the levels of c14 in organic tissue.
AMS technology has allowed us to date very small samples (such as seeds) that were previously undatable.
Modern AMS (accelerator mass spectroscopy) methods require tiny amounts, about 50 mg.The collagen fraction usually yields more reliable dates than the apatite fraction (see Dates on bones).In addition to various pre-treatments, the sample must be burned and converted to a form suitable for the counter. Since carbon is fundamental to life, occurring along with hydrogen in all organic compounds, the detection of such an isotope might form the basis for a method to establish the age of ancient materials.
Libby, a Professor of Chemistry at the University of Chicago, predicted that a radioactive isotope of carbon, known as carbon-14, would be found to occur in nature.
The ensuing atomic interactions create a steady supply of c14 that rapidly diffuses throughout the atmosphere.