text: Radiocarbon dating has been used since 1946 to determine the age of organic material as old as 50,000 years. As the organism dies, the exchange of C with the environment ceases and the incorporated C decays. Given the steady decay of radioisotopes (the half-life of C is about 5,730 years), the relative amount of C left in the dead organism can be used to calculate how long ago it died. Bomb pulse dating should be considered a special form of carbon dating. As discussed above and in the Radiolab episode, Elements (section Carbon),  in bomb pulse dating the slow absorption of atmospheric C by the biosphere, can be considered as a chronometer. Starting from the pulse around the years 1963 (see figure), atmospheric radiocarbon relative abundance decreased by about 4% a year. So in bomb pulse dating it is the relative amount of C in the atmosphere that is decreasing and not the amount of C in a dead organisms, as is the case in classical radiocarbon dating. This decrease in atmospheric C can be measured in cells and tissues and has permitted scientists to determine the age of individual cells and of deceased people. These applications are very similar to the experiments conducted with pulse-chase analysis in which cellular processes are examined over time by exposing the cells to a labeled compound (pulse) and then to the same compound in an unlabeled form (chase). Radioactivity is a commonly used label in these experiments. An important difference between pulse-chase analysis and bomb-pulse dating is the absence of the chase in the latter.
  Around the year 2030 the bomb pulse will die out. Every organism born after this will not bear detectable bomb pulse traces and their cells cannot be dated in this way. Radioactive pulses cannot ethically be administered to people just to study the turnover of their cells so the bomb pulse results may be considered as a useful side effect of nuclear testing.