Radiocarbon dating the old stables
The proportion of carbon-14 to carbon-12 in the atmosphere therefore remains relatively stable at about 1.5 parts per billion.
One of the implied assumptions in radiocarbon dating is that levels of atmospheric carbon-14 have remained constant over time.
Their commercial rate (in 2008) is 5.00 per sample, which somewhat limits its accessibility to chronically under-funded archeological research projects.
In the figure right, the production of radio-active carbon is demonstrated.
Here, 7 protons and 7 neutrons (N) plus one neutron form an isotope of carbon, with 8 neutrons and 6 protons.
First, the older the object, the less carbon-14 there is to measure.
Radiocarbon dating is therefore limited to objects that are younger than 50,000 to 60,000 years or so.