Radioactive dating no problem for the Bible
by Tas Walker
Photo iStockphoto
What about radioactive dating? Doesn’t that prove the world is millions of
years old? Radioactive dating may be one of the big questions looming in your mind.
But the idea of an unimaginably old earth did not come from radioactive dating.
It was popular long before radioactivity was discovered (see Western
Culture and the Age of the Earth). It came from a geologic philosophy, not
a scientific measurement.
Note too that radioactive dating is something that most people don’t understand.
Normal people are not familiar with isotopes, mass spectrographs, rubidium, strontium
or half lives. We find ourselves in the position where we are being asked to trust
the specialists, of not being able to check the facts first hand.
But it’s not difficult to understand the basic principles to realise that
alleged ages of millions of years have not been measured objectively, but derived
from subjective assumptions.
What is radioactive decay?
Radioactive dating begins by carefully measuring the concentrations of radioactive
isotopes in rocks. Everything is composed of elements and there are about 90 naturally
occurring ones, such as hydrogen, carbon, oxygen and iron. Each element comes in
different forms, called isotopes, most of which are stable and do not change. Some
isotopes, however, are unstable and decay radioactively into other elements. There
are many different radioactive isotopes that are used for radiometric dating.
For example, there is a radioactive form of potassium (potassium-40) that decays
into argon (argon-40). The unstable potassium isotope is called the parent while
the argon product is called the daughter. There are a couple of different radioactive
forms of uranium that decay into lead. There is a radioactive form of thorium that
also decays into lead. There is an isotope of samarium that decays into neodymium,
and one of rubidium that decays into strontium.
How does radioactive dating work?
we do not know how much of each isotope was in the rock in the beginning
Radioactive dating is often illustrated with an hour glass. The sand grains at the
top of the sealed glass are like the atoms of the parent isotope in the rock, and
those at the bottom like the atoms of the daughter. Radioactive decay is where the
parent atoms change as a result of radioactive decay into daughter atoms, like the
individual grains of sand falling from the top to the bottom of the glass. The hourglass
depends on the sand falling at a regular rate. Like an hour glass, it is said, you
simply measure the parent and the daughter elements and you can calculate the age.
What was the starting amount?
However, an hour glass is only useful if we saw it turned over and observed
that the bottom glass was empty. In other words, the hourglass only works when we
know its initial condition. Unlike the hourglass, we do not know how much of each
isotope was in the rock in the beginning. That’s because we did not observe
what happened in the past when the rock formed. Neither can we travel into the past
to make the necessary measurements. All we can do is guess. This is the fatal problem
that essentially makes radioactive dating useless as a primary method for determining
age.
Each dating method uses different kinds of assumptions to get around this problem
for radiometric dating—the deadly problem caused by the fact that we cannot make
measurements in the past.
Geologists don’t like to assume the amount of daughter directly (perhaps that
sounds like cheating), but they often do, and they call it a ‘model’
age. Geologists prefer to make indirect assumptions. They may assume that
different minerals in the rock originally had the same isotopic ratios to start
with. Or they may assume that different rock samples from the same geographical
area had the same ratio. Each dating method uses different kinds of assumptions
to get around this problem for radiometric dating—the deadly problem caused
by the fact that we cannot make measurements in the past.
Has the rock been disturbed?
Photo iStockphoto
Apart from the fatal problem of not knowing the initial conditions, there is another
problem that is just as deadly. We don’t know what happened to the rock during
its ‘lifetime’.
An hour glass is only useful if it is not disturbed. But after rocks crystallize
from molten magma, they can be heated and cooled; they can be affected by metamorphic
events and groundwater. These geologic events can cause elements to be gained and
lost to the rock. It’s like cracking the hourglass and having some of the
sand leak out, or other sand leak in. How can we know what disturbances have affected
the elements in our rocks? Again, we can only guess.
Every date has to be interpreted
Did you hear about the old wood cutter who was bragging about his axe? ‘I’ve
had this trusty axe for fifty years,’ he said. ‘It’s only had
two new heads and three new handles.’ The question is: how old was his axe?
It’s much the same with rocks. When a geologist hammers off a sample of rock
he needs to know its history. Different minerals would have crystallized at different
times depending on the way the molten magma cooled. Some small pieces of other rock,
or even some foreign minerals, may have been carried along by the magma and existed
long before the rock crystallized. Other minerals may have grown inside the rock
much later, during a time when the area was heated and metamorphosed. Some minerals
may have crystallized even later still when ground waters in the area percolated
through the pores of the rock. So the age of a rock is quite a complicated question,
and we first need to know its entire history before we can develop a story to explain
the isotopic measurements.
This means that, on its own, a radioactive ‘date’ is meaningless. Geologists
recognize this. You may be surprised to learn that a geologist would never collect
a rock at random and send it off for radioactive dating on its own. The result would
mean nothing. Every radioactive date has to be interpreted before anyone can say
what it means.
What happens is that the geologist will carefully record exactly where he collected
the rock. He explores the geology of the area so he can understand the geological
history, and where his particular sample fits into the sequence of geological events.
He checks out the ages other geologists have assigned to the different rocks in
the region. He studies samples of his rock under the microscope looking for clues
of how it crystallized, whether it was later heated, deformed, altered or weathered.
Then, when the laboratory sends him the ‘date’ for his rock, he can
decide what the date refers to. Does it represent the time the rock crystallized
or when it cooled? Or perhaps the date refers to the time when the rock was heated
or deformed or altered, or somewhere between two of these. Or maybe the date refers
to an earlier time, a time when the magma melted before the rock even formed. So
the geologist has a lot of options he can choose from as he develops a story to
explain the meaning of the date for his rock. He can even combine a number of different
explanations to explain his result.
radiometric dating never has the final word. It’s not objective like the lay-person
is led to believe.
And even after the geologist has interpreted his date and published his interpretation
in a journal, another geologist may later decide that there is a problem with that
interpretation, and say the date should be disregarded or reinterpreted.
So radiometric dating never has the final word. It’s not objective like the
lay-person is led to believe.
Has the decay rate ever changed?
An hourglass is only useful for telling time if the sand always falls at the same
rate. An hourglass can be disturbed if it tips over, is shaken, or gets moisture
inside.
Likewise, radioactive dating will only be reliable if the radioactive decay rate
of the isotopes has never been disturbed. Each different kind of isotope decays
at a regular, repeatable rate called its ‘half life’. It is generally
believed that the decay rates for isotopes would never change, even under the sorts
of conditions that could be experienced deep inside the earth, or even inside other
planets.
However, there is one survey of the scientific literature that refers to more than
two dozen experiments where changes in decay rates were reported.1 Laboratory experiments have quantified, for certain
radioactive decay processes, how much the rate is affected by the chemical and physical
conditions, but in these cases the changes observed are small.2 On the other hand, it has been demonstrated in the
laboratory that under certain conditions the radioactive decay rate can be accelerated
a billion fold. 3
Some may argue that these sorts of conditions would not apply on the earth, or that
the changes are only small in most cases. But in recent years, a group of seven
creationist research scientists, called the RATE group,4 has identified examples in the field that point
toward accelerated nuclear decay. 5
They have also developed a theoretical basis for how accelerated decay could occur.6
The fact is that we cannot travel into the past so we cannot know all the different
conditions that have existed on Earth and to which rocks may have been subject.
So, the idea that decay rates have remained absolutely constant over all time is
a belief, not a fact. And even secular scientists have sometimes proposed that the
decay rate changed in the past in order to resolve a disagreement between the age
of the earth and the age of the universe.
Not objective measurement, but subjective assumption
We are all familiar with measuring time so we should easily see that radioactive
dating is not everything it’s claimed to be. In an Olympic race, for example, the
official starts his stopwatch when the starting gun sounds. He stops his
watch when the athlete touches the finish line. He reads the time from
his watch. But what would happen if he missed the beginning of the race and only
saw the finish? It would be impossible for him to measure the time, no matter how
accurate his watch. We all know that, so we should all see the inherent problems
with radioactive dating.
Every ‘scientific’ dating method, including radioactive dating, needs
to know the initial conditions of the rock. But, unlike the Olympic official, we
were not present at the beginning so we can only assume how the rock formed
and what the conditions were. Not only that, but we must also assume what happened
to the rock during its lifetime.
Clearly, radioactive ‘dates’ are not independently-determined objective
measurements of age. Rather, all dates are based on subjective assumptions. And
because long-age researchers don’t take the Bible’s history seriously
they make assumptions that are inconsistent with it. That’s why their answers
contradict the Bible. But the numbers they quote are all based on assumptions and
don’t disprove the biblical timescale at all.
Further reading
Related resources
References
- Hahn, H.-P., Born, H.-J. and Kim, J.I., Survey on the rate
perturbation of nuclear decay, Radiochimica Acta 23:23–37,
1976. Return to text.
- Huh, C.-A., Dependence of the decay rate of 7Be on chemical
forms, Earth and Planetary Science Letters 171:325–328,
1999. Return to text.
- Woodmorappe, J.,
Billion-fold acceleration of radioactivity demonstrated in laboratory, Journal
of Creation 15(2):4–6, 2001. Return to
text.
- RATE stands for Radioactivity and the Age of The Earth. Return to text.
- Snelling, A.A.,
Radioisotope dating of rocks in the Grand Canyon, Creation 27(3):44–49,
2005. Return to text.
- Chaffin, E.F., Accelerated decay: theoretical considerations;
in: Vardiman, L. et al. (Eds.), Radioisotopes and the Age of the Earth
Vol. II, ICR, El Cajon, CA, CRS, Chino Valley, AZ, pp. 525–586, 2005.
Return to text.
Published: 30 April 2008(GMT+10)
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