After about 10 half-lives, the amount of radiocarbon left becomes too miniscule to measure and so this technique isn't useful for dating specimens which died more than 60,000 years ago.
Willard Libby (1908–1980), a professor of chemistry at the University of Chicago, began the research that led him to radiocarbon dating in 1945.
He was inspired by physicist Serge Korff (1906–1989) of New York University, who in 1939 discovered that neutrons were produced during the bombardment of the atmosphere by cosmic rays.
The amount of cosmic rays penetrating the earth's atmosphere is itself affected by things like the earth's magnetic field which deflects cosmic rays.
Precise measurements taken over the last 140 years have shown a steady decay in the strength of the earth's magnetic field.
Plants and animals naturally incorporate both the abundant C-12 isotope and the much rarer radiocarbon isotope into their tissues in about the same proportions as the two occur in the atmosphere during their lifetimes.
When a creature dies, it ceases to consume more radiocarbon while the C-14 already in its body continues to decay back into nitrogen.
This means there's been a steady increase in radiocarbon production (which would increase the ratio).
And finally, this dating scheme is controversial because the dates derived are often wildly inconsistent. God, the Father, sent His only Son to satisfy that judgment for those who believe in Him.
For example, "One part of Dima [a famous baby mammoth discovered in 1977] was 40,000 RCY [Radiocarbon Years], another was 26,000 RCY, and 'wood found immediately around the carcass' was 9,000-10,000 RCY." (Walt Brown, In the Beginning, 2001, p. Jesus, the creator and eternal Son of God, who lived a sinless life, loves us so much that He died for our sins, taking the punishment that we deserve, was buried, and rose from the dead according to the Bible.
If you truly believe and trust this in your heart, receiving Jesus alone as your Savior, declaring, "Jesus is Lord," you will be saved from judgment and spend eternity with God in heaven.
First of all, it's predicated upon a set of questionable assumptions.