5.3: What about Carbon-14 dating? (Creation versus Evolution)
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This article is from the Scientific Skepticism FAQ, by Paul Johnson Paul@treetop.demon.co.uk with numerous contributions by others.
5.3: What about Carbon-14 dating? (Creation versus Evolution)
Isotope dating takes advantage of the fact that radioactive materials
break down at a rate independent of their environment. Any solid
object that formed containing radioactive materials therefore steadily
loses them to decay. If it is possible to compare the amount of
radioactive material currently present with the amount originally
present, one can deduce how long ago the object was formed. The amount
originally present cannot, of course, be observed directly, but can be
determined by indirect means, such as identifying the decay products.
C-14 dating uses an unstable isotope of carbon that is constantly
being produced in the upper atmosphere by cosmic rays. This process is
assumed to be in equilibrium with the decay of C-14 throughout the
biosphere, so the proportion of carbon that is C-14 as opposed to the
stable C-12 and C-13 isotopes is essentially constant in any living
organism. When an organism dies, it stops taking up new carbon from
its environment, but the C-14 in its body continues to decay. By
measuring the amount of C-14 left in organic remains, one can
establish how long ago the organism they came from died. Because C-14
has a half-life of only a few thousand years, C-14 dating can only be
used for remains less than a few tens of thousands of years old--
after that, the C-14 is entirely gone, to all practical purposes.
Other isotopic dating techniques, such as potassium-argon dating, use
much longer-lived radionuclides and can reliably measure dates
billions of years in the past.
Actually the production rate isn't all that constant, so the amount of
C-14 in the biosphere varies somewhat with time. You also need to be
sure that the only source of carbon for the organism was atmospheric
carbon (via plants). The nominal date from a C-14 reading, based on
the present concentration, therefore has to be corrected to get the
real date --- but once the correction has been calculated using an
independent dating tool like dendrochronology (see below), it can be
applied to almost any sample.
There are some known anomalies in C14 dating, such as molluscs that
get their carbon from water. Creationists seem to make a habit of
taking samples that are known to be useless for C14 dating, presenting
them to scientists for examination, representing them as other than
they are, and then claiming the anomalous dates they get for them as
evidence that C14 dating is all a sham.
While it is true that there *may* be unknown errors in some dating
methods (see the note in section 0 about science "proving" things)
this assertion cannot be used to write off isotope dating as evidence
of an ancient Earth. This is because:
o There are several independent ways of dating objects, including
radio-isotopes, dendrochronology, position in rock strata etc.
These all give a consistent picture.
o Dating methods all point to an *old* Earth, about *half a million*
times older than the Creationists claim. This requires dating
methods which are accurate up to 6,000 years ago and then suddenly
start to give completely wrong (but still consistent) answers. Even
if our dating methods are out by a factor of 10 or 100, the earth is
still thousands of times older than Creationists claim.
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