Radioactivity and radioactive decay are spontaneous processes.
Students often struggle with this concept; therefore, it should be stressed that it is impossible to know exactly when each of the radioactive elements in a rock will decay.
This is also actually kind of trivial and easily determined in the lab. Let’s see what the Missing Universe Museum thinks are the assumptions of radioactive dating methods. I guess we have to start at the top and work our way down… During an organisms life, it takes in CO have the common 6 protons and 6 neutrons. However, due to some interesting nuclear chemistry (which I’ll go into if requested), there’s another version of carbon (called an isotope) that has 6 protons and 8 neutrons. Note that if the number of protons change, then the atom is no longer carbon. Amazingly (and unlike what is claimed by the creationists), scientists have known about a variety of methods that create carbon-14 and how those methods have varied over time. Well, we take a carbon sample from a material of a known age and date that. Basically, the calibration curves are off by no more than 16 years over the historical range (6,000 years or so) and no more than 163 years over the last 20,000 years.
Indeed, by doing almost 20 seconds of research on google (type in “variations in C14”, click on Google Scholar) the second link is this article from 1954: Carbon 13 in plants and the relationships between carbon 13 and carbon 14 variations in nature So, this issue has been known about for a long time. Then we compare the two and adjust the radiocarbon date to the known date. That’s less than 1% if you’re interested in that sort of thing. But this is already almost a thousand words and I’ve only done ONE! Long story short, scientists have always known that variations in C-14 concentration happen.
Obviously, this works only for things which were once living.
Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. Uranium has a very long half-life and so by measuring how much uranium is left in a rock its approximate age can be worked out.
The first is that atoms have always decayed at the same rate.
For example, in 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain.