Living organisms are continually taking in carbon-14 and so the ratio between C-14 and C-12 stays the same, but after the organism dies and is no longer taking in C-14, the C-14 level begins to decline.
Scientists have theorized that, by measuring the amount of carbon-14 left in the now-dead organism, they can date the time when it died.
It is only useful for once-living things which still contain carbon, like flesh or bone or wood.
Rocks and fossils, consisting only of inorganic minerals, cannot be dated by this scheme.
Basis of Radiocarbon Dating Problems with Radiocarbon Dating The Earth's Magnetic Field Table 1 Effect of Increasing Earth's Magnetic Field Removal of Carbon From the Biosphere Water Vapour Canopy Effect on Radiocarbon Dating Figure 1 Apparent Radiocarbon Dates Heartwood and Frozen Time Early Post-Flood Trees Appendix Radiocarbon Date Table HOW ACCURATE IS RADIOCARBON DATING? The normal carbon atom has six protons and six neutrons in its nucleus, giving a total atomic mass of 12.