It turns out that nuclear tests between 1955 and 1963 left their mark in every living organism on Earth, and scientists are able to use this fact to determine the age of cells in any living (at that time) creature on Earth and the frequency of their renewal, which would have been significantly more challenging without the nuclear tests. There is even a specific term “C-14 bomb-pulse dating”.
This is how radiocarbon analysis works. From 1955 to 1963, the use of atomic bombs doubled the amount of carbon-14 in the atmosphere. Atmospheric carbon-14, which is usually only produced by cosmic radiation, reacts with oxygen, forming carbon dioxide (¹⁴CO₂). This ¹⁴CO₂ is absorbed by plants during photosynthesis and then transferred into the human body directly through plant food and indirectly through the meat of animals, aligning its quantity roughly with the concentration in the atmosphere. Animals eat these plants, and we eat these animals—thus carbon-14 becomes incorporated into our bodies, integrating into our tissues.
Most tissues in living organisms gradually renew over weeks or months, so the carbon-14 content in them corresponds to the current atmospheric level. However, tissues that either do not renew or renew very slowly will contain a carbon-14 level close to that of the atmosphere at the time they were formed. Thus, by measuring the carbon-14 content in the tissues of people who lived during and after the peak of the “bomb pulse”, the rate of replacement of certain tissues or their components can be precisely estimated.
This means that nuclear tests, inadvertently, have provided scientists with a way to understand when tissues are formed, how long they last, and how rapidly they are replaced.
It turns out that practically every tree that has lived since 1954 contains a “spike” – a kind of souvenir from the atomic bombs. Wherever botanists look, they find this marker. There are studies in Thailand, studies in Mexico, studies in Brazil—wherever you measure the carbon-14 level, it’s there. All trees carry this “marker”—trees of northern latitudes, tropical trees, rainforest trees—it’s a worldwide phenomenon.
But there’s a catch. Every eleven years, the amount of carbon-14 in the atmosphere halves. Once the carbon-14 level returns to its original value, this method will become useless. Scientific American explains that “scientists have the opportunity to use this unique dating method only for a few decades until the carbon-14 level returns to normal.” This means that if they want to use this method, they need to hurry. Unless there are new nuclear explosions—but no one wants that.
Besides, this method enables the determination of a person’s age through their teeth and hair. Once a tooth is formed, the amount of carbon-14 in its enamel remains unchanged, making it an ideal tool for dating. Because certain teeth form at specific ages, measuring the 14C content in different teeth can help researchers estimate a range of birth years. The same holds true for hair, which grows about 1 cm per month, and conclusions can also be drawn from the carbon content in different parts of the hair.
About one-third of an entire tooth, or 100 milligrams, is needed for dating the carbon in teeth. To prepare the sample, it is ground and dissolved in acid, which releases CO2. With hair, instead of dissolving it in acid, it is burned. As hair has a high carbon content, only 3-4 milligrams of hair is needed. CO2 from the tooth or hair sample is then reduced to graphite—a crystalline form of carbon—and placed in an ion source at CAMS, where neutral graphite atoms are ionized by giving them a negative charge. The accelerator can then use this negative charge to speed up the sample, enabling detection, counting, and comparison of carbon isotope ratios. On graphs, pMC represents the ratio of concentrations.
In the 1960s, when the concentration of C-14 was sharply changing, the method allowed the determination of tissue age to an accuracy of ±1 year. However, after 2000, as the C-14 levels evened out, the accuracy dropped to ±2–4 years.
Hi, I'm Rauf Aliev. 