The rate of decay is considered constant and measurable, and is expressed by the term “half life.”Half life can be understood, for our purpose, by thinking of a block of ice. The time it takes to melt until it weighs only 5 pounds (half the original weight) is called its “half life.” For this example, let’s say the ice takes five hours to melt from 10 pounds down to 5 pounds. This is not exactly the way C-14 acts, but it serves our purpose.
Unlike ice melting, the half life of carbon and other unstable elements is constant.
Since scientists accept the concept of evolution, they conclude that the atmosphere is millions of years old.The carbon absorbed is both C-12 and C-14 and it is absorbed at the same ratio as it exists in the atmosphere.Once a living thing dies, it stops absorbing both C-12 and C-14.It would take an additional 5,730 years for the 50 pounds to decay to only 25 pounds, and so on, halving the amount of C-14 every 5,730 years.When C-14 is formed, it begins to break down into nitrogen as it loses an electron from the nucleus.