“Science has proved that the earth is 4.5 billion years old.”  We have all heard this claim.  We are told that scientists use a technique called radiometric dating to measure the age of rocks.  We are also told that this method very reliably and consistently yields ages of millions to billions of years, thereby establishing beyond question that the earth is immensely old – a concept known as deep time.

This apparently contradicts the biblical record in which we read that God created in six days, with Adam being made on the sixth day.  From the listed genealogies, the creation of the universe happened about 6000 years ago.  Has science therefore disproved the Bible?  Is radiometric dating a reliable method for estimating the age of something?  How does the method attempt to estimate age?

Can Science Measure Age?

People often have grave misconceptions about radiometric dating.  First, they tend to think that scientists can measure age.  However, age is not a substance that can be measured by scientific equipment.  The tools of science allow us to measure mass, volume, pressure, force, weight, and composition…  but not age.  The former quantities are physical properties that can be directly measured using the right equipment.  But age is not a physical property.  It is conceptual.  Age is the concept of the amount of time an object has existed.  It is the present time minus the time at which the object came into existence.  The only way that this can be known scientifically is if a person observed the time of creation.

This may seem like a trivial or obvious point.  But it is a very important one.  One cannot measure the “amount of age” contained in something – as if age were a substance that accumulates over time.  Instead, it would be far more accurate to say that scientists attempt to estimate the age of something.  Thus, the “ages” assigned to rocks on the basis of radiometric dating are not measurements; rather they are estimates.  This is an important distinction because a measurement is direct, objective, repeatable, and relatively independent of starting assumptions.  An estimate, on the other hand, is indirect and highly dependent on starting assumptions.  Sometimes deep time advocates ignore this important distinction.

Of course, there is nothing wrong at all with attempting to estimate the age of something.  We simply need to remember that such estimates are not nearly as direct or objective as a measurement of something like mass or length – measurements that are directly repeatable in the present.  And, as we will find below, age estimates are highly dependent upon starting assumptions.

Estimating Age

Since age cannot be measured, how is it estimated?  This is done by measuring a proxy and performing a calculation.  In science, a proxy is something that substitutes for something else and correlates with it.  As one example, age is not a substance that accumulates over time, but dust is.  The amount of dust can serve as a proxy for the amount of time since a room was last cleaned.  Though age cannot be measured, the depth of dust can be measured.  The estimated age is then computed based on the measured dust.

In order for this kind of estimate to work, certain assumptions must be used.  One set of assumptions concerns the initial conditions.  These are assumptions about the state of the system when it first started.  In the case of estimating the time since a room was last cleaned by measuring dust, we might reasonably assume that the room had zero dust at the time of its cleaning.  Presumably then, all the dust we measured has accumulated since the room’s last cleaning.

Another assumption concerns the rate of change of our proxy.  In this case, we must know something about the rate at which dust accumulates.  Often the rate can be measured in the present.  We might measure the amount of dust at one time, and then measure it again a week later.  We might find that dust accumulates at one millimeter per week.  But we must still make an assumption about the rate at which dust accumulated in the past.  Perhaps dust always accumulates at the same rate it does today.  But it is difficult to know for certain; hence, this remains an assumption.

Finally, we must make some assumptions about the “closed-ness” of the system.  In the case of our hypothetical example, we might assume that no one has gone into the room and added dust, or blown dust away using a fan.  The assumptions of initial conditions, rates, and closed-ness of the system are involved in all scientific attempts to estimate age of just about anything whose origin was not observed.

Suppose a room has 5 millimeters of dust on its surfaces.  If dust accumulates at one millimeter per week and always has, if no one has disturbed the room, and if the room started with zero dust at the time of its cleaning, we can reasonably estimate the time since the last cleaning as five weeks.  Our estimate will be as good as our assumptions.  If any of the assumptions is wrong, so will our age estimate be wrong.  The problem with scientific attempts to estimate age is that it is rarely possible to know with any certainty that our starting assumptions are right.

Radiometric Dating

In radiometric dating, the measured ratio of certain radioactive elements is used as a proxy for age.  Radioactive elements are atoms that are unstable; they spontaneously change into other types of atoms.  For example, potassium-40 is radioactive.  The number (40) refers to the sum of protons (19) and neutrons (21) in the potassium nucleus.  Most potassium atoms on earth are potassium-39 because they have 20 neutrons.  Potassium-39 and potassium-40 are isotopes – elements with the same number of protons in the nucleus, but different numbers of neutrons.

Potassium-39 is stable, meaning it is not radioactive and will remain potassium-39 indefinitely.  But potassium-40 will naturally transform (“decay”) into argon-40.  This happens when one proton in the potassium’s nucleus captures an orbiting electron, thereby converting into a neutron.[1]  This changes the atomic number of the atom from 19 to 18, and so the potassium atom becomes an argon-40 atom.  No external force is necessary.  The conversion happens naturally over time.

The time at which a given potassium-40 atom converts to argon-40 atom cannot be predicted in advance.  It is apparently random.  However, when a sufficiently large number of potassium-40 atoms is counted, the rate at which they convert to argon-40 is very consistent.  Think of it like popcorn in the microwave.  You cannot predict when a given kernel will pop, or which kernels will pop before other kernels.  But you can predict that after 2 minutes, 90% of the kernels will have popped.  It’s the same way with radioactive elements.  You cannot tell when a given potassium-40 atom will “pop” into argon-40.  But the rate of a large group of them is such at after 1.25 billion years, 50% of them will have converted to argon.  This number has been extrapolated from the much smaller fraction that converts in observed time frames.

The time it takes for 50% of a radioactive substance to decay is called the half-life.  Different radioactive elements have different half-lives.  The potassium-40 half-life is 1.25 billion years.  But the half-life for uranium-238 is about 4.5 billion years.  The carbon-14 half-life is only 5730 years.  Cesium-137 has a half-life of 30 years, and oxygen-20 has a half-life of only 13.5 seconds.  Why use “half-life” instead of “full-life”?  The answer has to do with the exponential nature of radioactive decay.  The rate at which a radioactive substance decays (in terms of the number of atoms per second that decay) is proportional to the amount of substance.  So after one half-life, half of the substance will remain.  After another half-life, one fourth of the original substance will remain.  Another half-life reduces the amount to one-eighth, then one-sixteenth and so on.  The substance never quite vanishes completely, until we get down to one atom, which decays after a random time.

Since the rate at which various radioactive substances decay has been measured and is well known for many substances, it is tempting to use the amounts of these substances as a proxy for the age of a volcanic rock.[2]  For example, suppose a rock contains 2 micrograms of potassium-40.  After 1.25 billion years, the rock will have only 1 microgram of potassium-40, and will have gained some argon-40.  So, if you happened to find a rock with 1 microgram of potassium-40 and a small amount of argon-40, would you conclude that the rock is 1.25 billion years old?  If so, what assumptions have you made?

The Assumptions of Radiometric Dating

In the previous hypothetical example, one assumption is that all the argon-40 was produced from the radioactive decay of potassium-40.  But is this really known?  How do you know for certain that the rock was not made last Thursday, already containing significant amounts of argon-40 and with only 1 microgram of potassium-40?  In a laboratory, it is possible to make a rock with virtually any composition.  How can we know that the laboratory of nature didn’t make the rock with such a composition very recently?  Ultimately, we cannot know.

But there is a seemingly good reason to think that virtually all the argon-40 contained within a rock is indeed the product of radioactive decay.   Volcanic rocks are formed when the lava or magma cools and hardens.  But argon is a gas.  Since lava is a liquid, any argon gas should easily flow upward through it and escape.  Thus, when the rock first forms, it should have virtually no argon gas within it.  But as potassium-40 decays, the argon-40 content will increase, and presumably remain trapped inside the now-solid rock.  So, by comparing the argon-40 to potassium-40 ratio in a volcanic rock, we should be able to estimate the time since the rock formed.

This is called a model-age method.  In this type of method, we have good theoretical reasons to assume at least one of the initial conditions of the rock.  The initial amount of argon-40 when the rock has first hardened should be close to zero.  It sounds pretty reasonable, doesn’t it?  Yet we know that this assumption is not always true.  We know this because we have tested the potassium-argon method on recent rocks whose age is historically known.  That is, brand new rocks that formed from recent volcanic eruptions such as Mt. St. Helens have been age-dated using the potassium-argon method.  Their estimated ages were reported as hundreds of thousands of years based on the argon-40 content, even though the true age was less than 10 years.

Since the method has been shown to fail on rocks whose age is known, would it make sense to trust the method on rocks of unknown age?  We might ask, “Why did the method fail?”  It seems that at least in some cases the assumption that lava cannot hold significant amounts of argon-40 is simply false.  Deep time advocates blame the faulty results on “excess argon.”  The initial amount of argon in the newly formed rocks was apparently not zero, and this false assumption led to the wrong answer.  But many secular scientists continue to trust the potassium-argon model-age method on rocks of unknown age.  But isn’t it possible that they also have excess argon?  If so, then their true ages are much less than their radiometric age estimates.  The age estimate could be wrong by a factor of hundreds of thousands.  But how would you know?

We must also note that rocks are not completely solid, but porous.  And gas can indeed move through rocks, albeit rather slowly.  So the assumption that all the produced argon-40 will remain trapped in the rock is almost certainly wrong.  And it is also possible for argon-40 to diffuse into the rock of course, depending on the relative concentration.  So the system is not as closed as secularists would like to think.

There are some mathematical methods by which scientists attempt to estimate the initial quantity of elements in a rock, so that they can compensate for elements like argon-40 that might have been present when the rock first formed.  Such techniques are called isochron methods.  They are mathematically clever, and we may explore them in a future article.  However, like the model-age method, they are known to give incorrect answers when applied to rocks of known age.  And neither the model-age method nor the isochron method are able to assess the assumption that the decay rate is uniform.  As we will see below, this assumption is very dubious.


Years ago, a group of creation scientists set out to explore the question of why radiometric dating methods give inflated age estimates.  We know they do because of the aforementioned tests on rocks whose origins were observed.  But why?  Which of the three main assumptions (initial conditions are known, rate of decay is known, the system is close) is false?  To answer this question, several creation geologists and physicists came together to form the RATE research initiative (Radioisotopes and the Age of The Earth).  This multi-year research project engaged in several different avenues of study, and found some fascinating results.

As mentioned above, the isochron method uses some mathematical techniques in an attempt to estimate the initial conditions and assess the closed-ness of the system.  However, neither it nor the model-age method allow for the possibility that radioactive decay might have occurred at a different rate in the past.  In other words, all radiometric dating methods assume that the half-life of any given radioactive element has always been the same as it is today.   If that assumption is false, then all radiometric age estimates will be unreliable.  As it turns out, there is compelling evidence that the half-lives of certain slow-decaying radioactive elements were much smaller in the past.  This may be the main reason why radiometric dating often gives vastly inflated age estimates.

First, a bit of background information is in order.  Most physicists had assumed that radioactive half-lives have always been what they are today.  Many experiments have confirmed that most forms of radioactive decay are independent of temperature, pressure, external environment, etc.  In other words, the half-life of carbon-14 is 5730 years, and there is nothing you can do to change it.  Given the impossibility of altering these half-lives in a laboratory, it made sense for scientists to assume that such half-lives have always been the same throughout earth history.

But we now know that this is wrong.  In fact, it is very wrong.  More recently, scientists have been able to change the half-lives of some forms of radioactive decay in a laboratory by drastic amounts.[3]  For example, Rhenium-187 normally decays to Osmium-187 with a half-life of 41.6 billion years.  However, by ionizing the Rhenium (removing all its electrons), scientists were able to reduce the half-life to only 33 years!  In other words, the Rhenium decays over 1 billion times faster under such conditions.  Thus, any age estimates based on Rhenium-Osmium decay may be vastly inflated.

Accelerated Radioactive Decay

The RATE research initiative found compelling evidence that other radioactive elements also had much shorter half-lives in the past.  Several lines of evidence suggest this.  But for brevity and clarity, I will mention only one.  This involves the decay of uranium-238 into lead-206.

Unlike the potassium-argon decay, the uranium-lead decay is not a one-step process.  Rather, it is a 14-step process.  Uranium-238 decays into thorium-234, which is also radioactive and decays into polonium-234, which decays into uranium-234, and so on, eventually resulting in lead-206, which is stable.  Eight of these fourteen decays release an alpha-particle: the nucleus of a helium atom which consists of two protons and two neutrons.  The helium nucleus quickly attracts a couple of electrons from the environment to become a neutral helium atom.  So, for every one atom of uranium-238 that converts into lead-206, eight helium atoms are produced.  Helium gas is therefore a byproduct of uranium decay.

And since helium is a gas, it can leak through the rocks and will eventually escape into the atmosphere.  The RATE scientists measured the rate at which helium escapes, and it is fairly high.  Therefore, if the rocks were billions of years old, the helium would have had plenty of time to escape, and there would be very little helium in the rocks.  However, the RATE team found that rocks have a great deal of helium within them.  In fact, the amount of helium in the rocks is perfectly consistent with their biblical age of a few thousand years!  It is wildly inconsistent with billions of years.

But the fact that such helium is present also indicates that a great deal of radioactive decay has happened; a lot of uranium atoms have decayed into lead, producing the helium.  At the current half-life of uranium-238, this would take billions of years.  But if it actually took billions of years, then the helium would have escaped the rocks.  The only reasonable explanation that fits all the data is that the half-life of uranium-238 was much smaller in the past.  That is, in the past, uranium-238 transformed into lead-206 much faster than it does today.

The RATE team found similar evidence for other forms of radioactive decay.  Apparently, during the creation week and possibly during the year of the global flood, radioactive decay rates were much faster than they are today.  The RATE team also found that the acceleration of radioactive decay was greater for elements with longer half-lives, and less for elements with shorter half-lives.[4]  So, slow-decay chains like uranium-lead, potassium-argon, and rubidium-strontium were drastically accelerated, while faster decaying elements like carbon-14 were only minimally affected.

All radiometric dating methods used on rocks assume that the half-life of the decay has always been what it is today.  But we now have compelling evidence that this assumption is false.  And since the decay rate was much faster in the past, those who do not compensate for this will end up with age-estimates that are vastly inflated from the true age of the rock.  This of course is exactly what we observe.  We already knew that radiometric dating tends to give ages that are much older than the true age.  Now we know why.

Carbon Dating

For whatever reason, many people have the false impression that carbon dating is what secular scientists use to estimate the age of earth rocks at billions of years.  It isn’t.  Carbon dating is not used on rocks, because rocks do not have much carbon in them.  And with a half-life of only 5730 years, carbon-14 does not last long enough to give an age estimate if something were truly millions of years old.  All the carbon-14 would be gone after one million years.  To estimate the ages of rocks, secular scientists use elements with much longer half-lives, such as uranium-238, potassium-40, and rubidium-87.

Animals and plants contain abundant carbon.  Carbon dating is therefore used most frequently on animal or plant remains.  The method gives an estimation of how long ago the organism died.

Most carbon is c-12; the nucleus contains six protons and six neutrons.  Carbon-12 is stable.  A small fraction of carbon is c-14, which contains eight neutrons rather than six.  Carbon-14 is produced in the upper atmosphere when cosmic rays produce neutrons that interact with nitrogen atoms, converting them to c-14.  The c-14 naturally decays back into nitrogen-14 with a half-life of 5730 years.  For this reason, at any given time, a small fraction of the carbon in earth’s atmosphere is c-14.

Plants extract carbon from the carbon dioxide in earth’s atmosphere, and since a small fraction of that carbon is c-14, plants do contain some c-14.  Animals then eat the plants, by which c-14 is integrated into their body.  So all plants, animals, and people have a small, but measurable quantity of c-14 in their body.  That c-14 is slowly but continually decaying into nitrogen.  But, while alive, plants and animals replenish the c-14 by taking in additional carbon from their environment.  Therefore, the ratio of c-14 to c-12 in a living animal or plant is roughly the same as it is in the atmosphere.

But when an organism dies, it ceases to replenish its supply of c-14.  The c-14 simply decays, and therefore the c-14 to c-12 ratio in a dead organism will be somewhat less than that of the atmosphere.  The older the organism, the lower the ratio.  So, the ratio of c-14 to c-12 in animal or plant remains serves as a proxy for age, and can be used to estimate how long ago the organism died.  Unlike rock-dating methods, carbon-dating tends to give the correct answer when tested on material whose age is known.  We therefore have more confidence in carbon-dating methods than we do in these other methods, though none are perfect of course.

Interestingly, many fossils of plants and animals often contain some of the original material of the organism – including carbon.  When this occurs, we can measure the ratio of c-14 to c-12 in these remains, and estimate the age.  And what do we find?  Very consistently, carbon-dating gives ages that confirm the biblical timescale of thousands of years.  Even when we test specimens that evolutionists believe to be millions of years old, such as coal beds, carbon-dating consistently reveals age estimates of a few thousand years.  Yes, there are measurable levels of c-14 in coal, which would be utterly impossible if coal were millions of years old.

We have even carbon dated dinosaur fossils, and the age estimates always are in the range of thousands of years – never millions.  The RATE team even found c-14 in diamonds that secularists believe to be billions of years old.  But after 1 million years, no c-14 would remain.  Therefore, diamonds are only thousands of years old at most.  Most evolutionists don’t even bother to carbon date things like dinosaur remains because they believe such remains to be millions of years old.  And there would be no c-14 left in such a specimen.  But there always is.  Without fail, carbon-dating confirms the biblical timescale.

Even carbon dating has its assumptions of course.  One of those is the assumption that the c-14 to c-12 ratio in the atmosphere has always been constant.  But we would not expect that to be the case.  The earth may have had very little c-14 in its atmosphere when God first created it.  It takes time for c-14 to build-up.  Moreover, the earth had a stronger magnetic field in the past which deflects cosmic rays and would tend to reduce c-14 production.  At the time of the worldwide flood, creation scientists believe that the atmosphere had only a small fraction of its current level of c-14.  If we neglect this then our age-estimates will be inflated by a factor of ten or so.  Therefore, we expect that when carbon-dating is applied to organisms that perished in the global flood, their estimated ages (~50,000 years) will be roughly ten times larger than their true age (~5,000 years).  This is exactly what we find.  However, if these remains were millions of years old, there should be no c-14 left in them, which is not what we find.


Radiometric dating has been demonstrated to give wrong age estimates on rocks whose age is known.  Yet, secularists continue to assume that it gives correct age estimates on rocks of unknown age.  We now have a good idea why most radiometric dating methods give inflated ages: there was at least one episode of accelerated radioactive decay in earth’s history.  This is the only reasonable way to make sense of the abundance of helium found trapped in various rocks.  The abundance of helium indicates that much radioactive decay has happened.  But if it had happened slowly over billions of years, then the helium would have diffused out of the rocks long ago.

One of the few radiometric dating methods that gives consistently reliable results when tested on objects of known age is carbon dating.  But carbon dating confirms the biblical timescale of thousands of years.  It never gives age estimates of billions or even millions of years – even on things evolutionists believe to be very old like coal and diamonds.  Carbon dating of dinosaur remains confirms their biblical age of thousands of years.  When we understand the science, we find that radiometric dating actually confirms the biblical account of history.


[1] Potassium-40 can also decay into Calcium-40 by beta decay.  One neutron converts into a proton, ejecting an electron in the process.  This is the most common decay path for potassium-40, accounting for 89% of the decay product.  The remaining 11% convert to argon-40 by electron capture.

[2] Generally, radiometric dating is only used on igneous rocks; rocks that have formed from magma or lava.  The change from liquid to solid sets the “clock” to zero since the elements can no longer move around freely.  Therefore, sedimentary and metamorphic rocks cannot be radiometrically dated because they were not liquid at the time of their formation.

[3] https://answersingenesis.org/geology/radiometric-dating/acceleration-of-radioactivity-shown-in-laboratory/

[4] They also found some evidence that alpha decay chains were accelerated somewhat more than beta decay chains.