This value of 0.2 p MC is very close to the value of 0.195 p MC found within Figure 1.About nine half-lives would have to elapse for a starting value of 100 p MC to decrease to 0.2 p MC.One of these assumptions is that nuclear decay rates have always been constant.
Finally, although contamination can sometimes occur, it should not be assumed in a particular instance unless there are good reasons to believe that it has.
Second, such large calculated ages are based on the C/C ratio has remained unchanged for tens of thousands of years.
A global flood like the one described in the Bible would invalidate this assumption.
And 4,500 years is less than one radiocarbon half-life, so from Figure 2 we might expect 4,500-year-old samples to have C found within organic samples thought to date from the time of the Flood is generally only about 0.1 to 0.5 p MC.
From Figure 1, a value of 0.098 ≈ 0.1 p MC corresponds to 10 half-lives, or about 57,000 years.