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You can’t rely on Carbon-14 dating anymore. The Japanese scientists recently discovered that lightning is hot enough to convert, via thermonuclear fusion, some normal C12 into C14. Thus, the amount of C14 is increasing all the time, so you can’t just look at how much C12 is left, because we no longer have a fixed starting point.

Thus, the amount of C14 is increasing all the time, so you can’t just look at how much C12 is left, because we no longer have a fixed starting point.

One approach to radioactive dating is to measure the amount of C14 as well as the quantity of the nuclear decay products. The current quantity of the radioisotope + the decay products tells you the original quantity of the radioisotope. Once you know the original and the current quantities, you can figure out how many half lives have elapsed.

Much C14 dating is done by comparing the ratio of C14 to C12. That also gives a good idea of the elapsed time since the organism died.

C14 is constantly being created through interactions of cosmic rays with the atmosphere, and the quantity of C14 ingested by living organisms is proportional to their size. Once they die, they no longer ingest C14. The rate of formation of C14 is almost constant. It probably varies slightly with the activity of the sun, but since the suns activity also cycles, the variations are evened out over time.

The Khan on-line academy has a couple of lessons on C14 dating. Once you do the math yourself, you get a much better understanding of the methodology.

You really missed class the day they covered C14 dating didn't you. The whole point is that c14 is constantly created by natural processes cosmic rays mostly and promptly begins decaying so we reach what is called a "steady state" for C14 in the environment where the rate of formation equals the rate of decay.

When something dies it becomes isolated from c14 uptake - dead things don't eat. So the steady state level of c14 begins to decay at the ~12,000 year half life. An artifact with half the environmental norm of c14 is 12k years old. One with 1/4 the steady state is 24k years old etc.

Not enough Carbon-14 (radiocarbon, C-14, 14C) would be created by lightning to significantly alter 14C dating, however, there are significant fluctuations in the normal 14C creation process (perhaps due to fluctuations in solar radiation or cosmic rays - by which the vast majority of 14C is generated - or other factors like ‘nearby’ novae or supernovae). So there are plenty of reasons to distrust that dating technique, but lightning isn’t a big enough player compared to the Sun to really matter.