I’m confused about Carbon-14 dating. What is it based on? (besides the
amount of radioactive carbon in an organism and its atmosphere at a given
time) I know that it is extremely inaccurate, but what is it that makes
scientists somewhat believe that it works?

Carbon-14 dating works on the basis of the fact that in
naturally-occurring carbon dioxide in the atmosphere there is a very
small, but predictable level of the radioactive isotope of carbon, C-14.
The emissions from this element are very predictable, making it rather
easy to measure the level of the isotope in a sample. The fact is that
this isotope has a half life of about 5,740 years. If one can assume that
the level of C-14 in the air is approximately constant, then one can take
the amount of C-14 in any sample of organic matter and calculate how long
ago the material was alive. The calculation and even the method are quite
simple and are a standard technique used today to date archaeological

You should be aware that the method is only useful for
relatively young samples. For objects more than about 30,000 years old,
the level of C-14 is so low that the method is not useful. Therefore,
Carbon-14 is not relevant to such issues as how old the earth is, or how
long ago such creatures as the dinosaurs lived, or even of the most
ancient early human remains. You imply in your question that this method
is extremely inaccurate. That is simply not true. It is possible to take
samples whose age we know from other sources (dates of pottery shards,
dates of destruction of cities and so forth) and the method turns out to
be accurate to within less than ten percent. Beyond about 3000 years of
age, the method has to become somewhat less certain simply because we do
not have solid historical markers to compare, and because it is difficult
to prove beyond a reasonable doubt that the C-14 levels have remained
constant. Nevertheless, it is perfectly reasonable to assume that C-14
dating is at least acceptably accurate out to the maximum range of its
effectiveness: about 30,000 years.

The persistent rumors that C-14 is an unreliable method is,
unfortunately, at least partially supported by defensive “Christian”
groups who are trying to defend a very recent creation date for the
earth. Whether or not the earth is actually young or old will ultimately
not be answered by C-14 dating, since it is only good to several thousand
years, but it is unfortunate that supposed Christians have made false
statements about the reliability of C-14 dating because they are not
willing to accept the implications of what we learn from this important
scientific tool.

John Oakes, PhD

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