Carbon-14 Activity during the Past 5,000 Years

Abstract

IN a recent communication, C. Crowe¹ uses published dates on samples of known age in an attempt to investigate variations of the concentration of carbon-14 in living material during the past 5,000 years. He concludes that the activity has followed a cycle with a maximum change of 10 per cent and with some evidence of a sharp peak of about 10 per cent about 2,000 years ago. His proposed curve is most striking, for the effect, if real, would imply, for example, that all 1,000-year old samples should give radiocarbon ages of more than 1,700 years, a result which has not yet been obtained in practical measurement despite the growing number of accurate measurements on tree rings and other materials of known age.