Original Articles: 2

! Although the decay of Carbon-14 into Nitrogen-14 with a half life of 5730 years can act as a regular counting device with which to derive a mathematically calculated age of an organic material, its actual age depends on the proportion of Carbon 14 to Carbon 12 there was in the material when the carbon atoms became part of it, and this has varied through history. In some cases, a single calculated date Before Present (BP) derived from C14 decay can convert to several possible calendar dates. We know this is true because of several dendrochronological studies, and attribute it to variations in the cosmic radiation causing variations in atmospheric C14 generation. For this reason every radiocarbon calculation must be calibrated against a recognised reference curve in order to produce an accurate calendar date. An extract from the most recent of these is shown below.(1)