Carbon dating artefacts
But as more dates became available, Egyptologists, who had hieroglyphic records back thousands of years, began to recognize that C-14 dates were generally too young.
They proved this by showing that C-14 dates of wooden artifacts with cartouches (dated royal names) did not agree.
is a term for radiocarbon dating based on timestamps left by above-ground nuclear explosions, and it is especially useful for putting an absolute age on organisms that lived through those events.
In The Cosmic Story of Carbon-14 Ethan Siegel writes: The only major fluctuation [in carbon-14] we know of occurred when we began detonating nuclear weapons in the open air, back in the mid-20th century.
They have the same ratio of carbon-14 to carbon-12 as the atmosphere, and this same ratio is then carried up the food chain all the way to apex predators, like sharks.
But when gas exchange is stopped, be it in a particular part of the body like in deposits in bones and teeth, or when the entire organism dies, the ratio of carbon-14 to carbon-12 begins to decrease.
One standard deviation has a 68% probability and two standard deviations have a 95% probability.
Radiocarbon dating has had an enormous impact on archaeology around the world since it made it possible to date carbon and wood could be directly without dependence on characteristic artifacts or written historical records.
As we mentioned above, the carbon-14 to carbon-12 ratio in the atmosphere remains nearly constant.
Another problem derives from the “reservoir effect” in which old material, limestone or graphite, has contaminated the samples.
This is particularly true of marine samples and contemporary shells may seem to be hundreds of years old.
The explanation was that the physicists had assumed that the amount of C-14 in the atmosphere had been constant, when in fact it had varied over time.
The solution came using dendrochronology (tree ring dating).