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radiocarbon dating, these and other
basic unanswered problems plague the
researchers. There is no way to get away
from assumptions for the prehistoric
period.
In order to postulate the relative con–
stancy of carbon-14, severa! other
assumptions had to be made.
One basic assumption is that, "The
cosmic-ray flux, and, hence, the
PRO·
DUCTION RATE
of radiocarbon in the
atmosphere has remained constant for
severa! half-lives [the half-life of car–
bon-14 is presently calculated at 5730+
30 years]." (Hans
E.
Suess, "Secular
Variations of the Cosmic Ray Produced
Carbon-14 in the Atmosphere,"
Journal
of Geophysica/ Research,
Vol. 70, No.
23, December 1, 1965, p. 5937.)
Dr. Suess 1fso gives another related
assumption
CH.
the same page: "Carbon
contents of the various reservoirs con–
taining cosmic-ray-produced
CJ4
have
remaioed constant over such a period of
time." (lbid., p. 5937.)
For carbon-14 dating to be valid,
even a third assumption is needed. The
"rates of
CJ4
transfer from the atmo–
sphere into the other reservoirs, in par–
ticular into the oceans, have also
remained constant over this length of
time." ( Ibid., p. 5937.)
These assumptions really could not
be proven. But they are accepted on the
premise that the present is the key to
the past. It was assumed that no
extraordinary occurrences had disturbed
the production of carbon-14 or other
related factors. This fundamenta.! belief
was a híghly dangerous assumption to
make. But made ít was!
"lt
is generai!y accepted that during
the last 8000 years
NO LARGE
changes
over prolonged intervals of time have
occurred in the average cosmic flux, in
the magnitude of the magnetic field in
the vícinity of the earth, and in the
degree of mixing in ocean water." (E.
l.
Hamilton,
Applied Geochronology,
London: Academic Press, 1965, p. 35 .)
Searching for the Answers
It is difficult - if not impossible -
for scientists to prove that these crucial
assumptions of the radiocarb.on method
are correct. As one example, come into a
laboratory to see what researchers found
The
PLAIN TRUTH
in trying to prove one of them.
The problem is: Assumed equilibrium
between production and disintegration
of carbon-14. This assumption is basic
to the method.
In the later 1940's, Dr. Willard
Libby and his associates set up experi–
ments to discover the present produc–
tlon cate of radiocarbon. They handled
the problem in this manner . They first
calculated the average production rate of
free neutrons in the outer atmosphere.
(Neutrons, produced by the cosmic
rays, are the key factor in the produc–
tion of carbon-14.)
Once Dr. Libby established a
present
average production rate of neutrons, he
calculated the present pcoduction rate of
carbon-14.
Next, Dr. Libby proceeded to calcu–
late the average rate of decay of carbon-
14 in modern living organisms.
Finally, he calculated the total amount
of carbon in the world exchange reser–
voir. This was necessary because a
radiocarbon date depends on the
RATIO
of carbon-14 to ordinary carbon. With
this information aod other critica! facts,
radiocarbon dating seemed to be on its
way.
Plunging Into The Unknown
At tbis stage, everything seemed quite
plausible.
It
was all a matter of chem–
istry, physics and mathematics.
Now, Dr. Libby was required to make
one
basic assmnption.
It did not neces–
sarily invalidate the method, but if this
assumption we.re incorrect, it would
have grave implications for certain
ranges of dates. It was also crucial in
terms of the time of the
beginning
of
radiocarbon in the living carbon cyde
of the earth.
The assumption and its implication
are the following:
As mentioned, cosmic ray particles
produce free neutrons when they smash
into the atmosphere. These neutroos
react with nitrogen atoms. A neutron,
when it enters the nitrogen nudeus,
knocks out a proton, which converts the
nitrogen atom toa carbon-14 atom.
Libby calculated the
PRESENT PRO·
DUCTION RATE
of these carbon-14
atoms. Now, if the
present P''oduction
has been going on for thousands upon
thousands of years at its present rate,
March, 1970
then the followíng evídence
tntlst
be
formd:
"If
this production has proceeded at
a constant rate for many thousands of
years, then the amount of
0
4
present
on the surface of the earth should reach
a
CONSTANT
value'' ("Radiocarbon
Dating,"
McGt'aUJ-Hill Encyclopedia of
Science and Technology,
1966 edition,
Vol.
11,
p.
291).
This "constant" amount was further
explained by Dr. Libby himself. "... We
can see that if the cosmic rays
have been bombarding the earth in
essentially
THEIR PRESENT INTENSITY
for 10 or 20 thousand years, we can
expect that
A STE.ADY·STATE COND!TION
had been establisbed, in which the rate
of formation of carbon-14 is equal to
the rate at which it disappears" (Will–
ard F. Libby, ' 'Radiocarbon Datiog,"
America11 Srientist,
Vol. 44, No. 1, Jan–
uary, 1956, p. 99) .
In other words, on this assumption
the carbon-14 ratio of any ancieot speci–
men could be related to the present ratio
of carbon-14 in modero specimens.
Dating then becomes simple.
lf no other
tmk,town facton
had disrupted the
method, a radiocarbon year would equal
a calendar year.
An analogy explains why this equili–
brium is vital.
Suppose There Is No
Equilibrium
Think of a bathtub filling with water
- but without a plug in
it.
If
the tap
pours water into the tub at a constant
rate, the level of water in the tub will
reach a constant height. This height
will remain unchanged. In other words,
the amount of water pouring into the
bathtub will
jmt eqttal
the amount of
water draining out through the plug
hole. The idea being that the produc–
tion of carbon-14 equals the amount
leaving the system in disintegration.
In terms of the bathtub, it takes only
a few minutes to establish this equili–
brium. However, it would take a long
time to bring the radiocarbon leve! into
equilibrium.
If
the system is not yet in equili–
brium, it simply means not enough car–
bon-14 has been produced to fill up the
atmospheric bathtub. And apparently