Did you know using Carbon-14 we can determine the age of artifacts? Where does this Carbon come from you ask: neutron containing cosmic rays when a star explodes. As these neutrons come in contact with the Earth and its nitrogen it creates Carbon-14!
From here the created Carbon-14 decays into electrons and nitrogen. You may notice that the cycle of Carbon-14 decaying and being created is a constant cycle, meaning it has a small but constant level in our atmosphere. This carbon also oxidizes into carbon dioxide.
Because the Carbon-14 oxidizes into CO2, it is also used in many natural processes that involves it like photosynthesis. This use of Carbon-14 in this process means that the matter in the plant (exposed to Carbon-14 during photosynthesis) contains small amounts of this isotope.
This same idea can be applied to animals too. When animals consume food and go through cellular respiration, Carbon-14 is transferred into their body because of the plant/animal that they ate that contains... you guessed it Carbon-14!
Sadly, things die and when death does occur the Carbon-14 in the animal/plant isn't replaced and will start to go away. Based on the half life of Carbon-14 (about 5,730 years) and the amount of non changing Carbon 12 in the artifact will give us a good idea of the age.
To find how much Carbon-14 is in an artifact we must use a machine called a Geiger Counter (Carbon-14 levels measured in counts per minute/cpm). From here we just plug in this information into the 2 equations that can eventually help us get the age of the artifact.