Voices of Science

Yes. The, yes, the thermonuclear tests produced huge amounts of Carbon-14 in the atmosphere, reaction of neutrons with nitrogen. And these tests of course peaked in the early ’60s. The Americans let a few off, and then the Russians let a couple off, and one of the Russian ones was absolutely huge. So this pulse of C14 entered the atmosphere, and then the plants, and then eventually the soil. Now I’d been radiocarbon dating soil organic matter and I was very much surprised, I was using old, stored samples, and much to my surprise the age came out to be, oh, thousands of years. The top soil 1,000 years, sub-soils down a metre or so, 10,000 years. I hadn’t expected this. In fact in one of my early papers I said that soil turnover is too fast for radiocarbon to be any use. [Laughs] A spectacular mistake [laughs]. Anyway, of course these thermonuclear tests took place and the pulse of C14 entered the plants and the soil and this gives you a way of following the entry of plant material into soil. And you could use the difference between the carbon content, the radiocarbon content, of the soil before the tests and after the tests as a way of calculating how much carbon goes into the soil each year from plants. But atmospheric testing was banned, and that was the end of those big tests. So since then the radiocarbon content of the atmosphere has been dropping back to its previous level. And in fact – there was a thing in the paper this morning, that people are able to detect wine that supposed to be [laughs] say laid down in 1960 from what – it was marked as laid down in 1960, but in fact was grown in 19, say, 90. You could tell. So and they have also applied this to whiskey. So people who have been lying about the age of their whiskey can be caught out [laughs].