by Jan Young



Scientists tell us that the earth is 4.5 billion years old. There are many ways to confirm this figure. The study of the origin of the universe points to it. The length of time required for life to spontaneously begin and to evolve to its present form points to it. The ages of the strata and the fossils point to it. And over the last half century, radioactive dating has verified this figure.

According to the geologic timetable, various life forms appeared at definite times in earth's history. Yet the geologic timetable dates back to the 1800s, before high-tech laboratory methods had been devised. How accurate is the timetable? Is there some way it can be independently verified?

The discovery of radioactivity and its application to the study of the earth's history was an important breakthrough for evolutionists. Radioactive dating gives precise figures. Using the scientific method, as explained in Chapter 2, tests can be run over and over again and checked by many scientists. Now scientists can prove beyond a shadow of a doubt that their dates are correct.


Rocks are made of various elements. In some rocks, some of the elements are radioactive. This means that in some elements, energy and subatomic particles may be emitted because of the breakdown of the nuclei of atoms. Radioactive elements disintegrate, or decay, into certain other elements.

The rate at which they decay is calculated by a unit of measurement called a half-life. A half-life is the length of time it takes for half the radioactive atoms to decay. After one half-life, half the radioactive atoms have decayed. After the next half-life, half the remaining radioactive atoms have decayed. And so on and so on.

Half-lives are not the same for all radioactive atoms.

They range from seconds, minutes, and days to well over billions of years. For example, the rate for potassium-40 is 1.3 billion years; for uranium-238, 4.5 billion years; for rubidium-87, 50 billion years; for uranium-235, 713 million years. Half-lives are important because they are used to determine the ages of rocks with radioactive elements.

Radioactive elements don't break down at a constant rate; the rate is continually declining. It is faster at first, and then gradually slows down. Scientists say that this breaking down of elements decreases at a known rate.

One element breaks down into another element. Uranium decays into lead, rubidium into strontium, and potassium into argon. These pairs of elements are used in radioactive dating methods called uranium/lead, rubidium/strontium, and potassium/argon.

The first in each pair (the original element) is called the "parent" element. The second (the product of decay) is called the "daughter" element. The daughter element is not radioactive and does not break down any further.

How does all this show the age of a rock? A math equation will give you the age of a rock, if, for example, you know the amount of uranium originally in the rock, the amount of uranium and lead in the rock now, and the rate that uranium decays into lead.

These methods can measure rocks that are millions and billions of years old. Another method measures the amount of the element carbon-14 in organic matter (plant or animal matter). This is called radiocarbon or carbon-14 dating. Radiocarbon dating is effective only on fossils up to around 50,000 years old.

Carbon-14 breaks down into nitrogen-14, and has a half-life of 5730 years. It enters plants and animals as they absorb carbon dioxide from the atmosphere or the food chain. When an organism dies, it stops taking in carbon-14. The carbon-14 begins to decay at a steady rate. Measuring the amount of carbon-14 in a fossil gives the date at which it died.


Radioactive dating seems to prove the long ages claimed by evolutionists. Radioactivity, half-lives and scientific laboratory tests are hard to argue with. But we will see that this dating method is based on some faulty, unprovable assumptions. We will see that the radioactive "clocks" in the rocks may not be very reliable time-keepers.

1. Initial Properties of Rocks

Note that the previous discussion on radioactive dating referred to rocks, not fossils. Carbon-14 dating is the only method that works on fossils themselves, but since it can only date fossils up to around 50,000 years old, it does not even begin to deal with the real issue of long ages.

Most fossils cannot be dated by radioactive methods. The rocks that the fossils are imbedded in usually cannot be dated radioactively either. As we have already seen, almost all fossils are found in sedimentary rock, and most sedimentary rock cannot be dated by radioactive means.

Generally speaking, only igneous (volcanic) rocks have radioactive elements. But fossils are seldom found in igneous rocks. The age of a fossil is the age of an igneous rock in the same strata, and as near to it as possible. A fossil may be dated by finding an igneous rock above and below it. By dating those rocks, it can be assumed that the age of the fossil falls in between those two ages.

To calculate the age of a rock, you need to know the initial amount of uranium in the rock (or of whatever parent element you are working with). How can the original amount of uranium in that rock be measured?

Scientists can't know for sure, but they can make assumptions. Using the uranium/lead method, for example, the scientists assume how much uranium was in the rock to begin with, and use this figure in their calculation. They also assume whether or not any lead, or daughter element, was in the rock to begin with. If they assume there was, then they must assume how much there was. Or they might assume there was no lead in the rock to begin with.

Since igneous rock originated within a volcano, we know it was transported and deposited somewhere else. Transported matter reflects the properties of its initial source area (the volcano), not its time or place of deposition. What can it tell about the strata of sedimentary rock in which it is found, or the fossils in that sedimentary rock?

It is impossible to know how much of the parent element and the daughter element were in the rock to begin with. The initial properties of the rock cannot be known for sure. The initial conditions that formed the rock cannot be known. It cannot be known if there were environmental changes that may have affected that rock. How those possible environmental changes affected the rock cannot be known. If any of the assumptions about the initial properties of the rock are wrong, the mathematical formula will give a wrong answer--a false age.

2. Rates Of Decay

In order to calculate the age of a rock, you must know the rate at which the parent element breaks down into the daughter element. Scientists claim that they know what this rate is, and that it does not change.

How do they discover the half-lives of elements? They measure the amounts of parent and daughter elements in a rock, then measure it again later. They compare the two measurements and note the length of time that has elapsed.

After the half-life is found, it is extended backwards in time by using mathematical formulas. There is no independent way to verify the result. It is based on mathematical calculations, not observation--similar to the reasoning that led to the Big Bang theory.

Radioactivity was discovered in the 1890s. The longest possible time lapse that can be measured and verified is therefore about 100 years. How can scientists be sure that the rate they observed extends unchanged over millions and billions of years? This belief is based on the assumption of uniformitarianism, which, as we saw in the last chapter, does not always hold true. There is no independent way to verify it. Assuming an unchanging rate is the only way radioactive dating can work, yet this is a massive extrapolation.

Care must be taken when extrapolating. For example, if you measure the growth rate of a human over a given period of his childhood, and then extrapolate that rate of growth over his entire lifetime, you can know how tall or heavy he will be at any given age. Right?

If a baby is born weighing seven pounds and doubles his weight in six months, you can figure out how much he will weight at age 30. You will have a scientific but false “fact.” It is obvious that extrapolation is not a principle that holds true in every situation.

In rocks containing radioactive elements, one substance is changing into another substance. But either substance may have some unknown amount of that element added to the rock from outside the rock, or some unknown amount may escape to the outside. If either of these possibilities happens, it happens at unknown rates. The length of time the process may have gone on cannot be known.

Isaac Asimov makes an interesting comment about dating methods in his book, Beginnings. He gives an example of an early attempt at earth-dating by measuring the rate of salt being deposited in the sea by rivers. He warns the reader that it was not a reliable method because of several problems: the unknown initial salt properties of the ocean, the unknown earlier rates of salt deposition in the ocean, the possibility of changing rates of deposition, and not knowing if any salt is either being added or escaping by other means.

These are the exact types of problems that plague the radioactive dating methods. Elsewhere in the book he states that radioactive substances breakdown at steady, known rates. He fails to point out that the faults of the salt method are also faults of the radioactive method.

When it comes to radioactive dating, scientists assume a constant rate of decay; they assume no gain or loss by leakage to or from outside; they assume initial conditions. How do they decide what rates and amounts to assume? According to Morris and Parker (What is Creation Science?), calculations are rejected that result in an earth that is too young to fit the evolutionary time scale. They accept calculations that result in an acceptable age. All variables are rejected that give too young of an age. The use of radioactive dating is based on a commitment to evolution and long ages.

Most scientists won't admit that these unknowns exist because steady, known rates are essential to the theory of evolution.

3. Disposable Dates

Are scientific conclusions based on the evidence? Or is the evidence interpreted or ignored to suit the preference of the scientist?

According to geologist Steven Austin, dates are discarded that do not match up with the date established by the geologic timetable, which always takes priority over radioactive methods, and establishes the framework that radioactive dates are made to fit into. However, Isaac Asimov maintains that radioactive dates are determined independently of fossils or any type of evolutionary philosophy.

Another reason for discarding dates is that a single rock may yield widely differing dates, or "discordant" dates; they can't all be true, so one must be kept and the others discarded. Wouldn't the solution to this dilemma be, to test the same rock by different methods? If each of the methods really works, the age of the rock should then be obvious.

Austin says he does not know of any potassium/argon date that agrees with any rubidium/strontium date for the same rock. He claims that lack of agreement among the different methods is perhaps the most serious indication of the unreliability of radioactive dating.

4. Errors In Dating

Recent radioactive testing at the Grand Canyon has turned up some surprising ages. Rubidium/strontium tests were done on two lava flow formations. The Cardenas Basalt, found in the oldest, deepest strata, tested at about 1.07 billion years old.

The western Grand Canyon lava flows are found on the Uinkaret Plateau north of the Colorado River. They are supposed to be some of the youngest formations found in the Grand Canyon, but they tested at roughly 1.34 billion years old, much older than the deeply buried Cardenas Basalt. The same equation was used on both samples to calculate the ages, and the samples were submitted independently to three different laboratories.

In June 1992, magma samples from the lava dome at Mount St. Helens in Washington, known to be ten years old, were tested by the potassium/argon method. Resulting dates ranged from about 340,000 to about 2.8 million years.


Radioactive dating has been cited by evolutionists as proof for the long ages needed for evolution to take place. Skeptics argue that this is debatable—not because of the techniques involved, but because of the assumptions used to interpret the data.

In order to calculate the date of a rock, its initial properties must be known, the rate of decay must be constant, and there must be no outside gain or loss of either parent or daughter element. These three facts must be known in order to set up a mathematical equation to calculate the age. But none of them can be known. An equation based on assumptions and extrapolations cannot be considered scientifically proven.

Radioactive dating is based on the concept of decay--the Second Law of Thermodynamics--the very law that is ignored in order to explain how evolution happened. We saw in Chapter 3 that many are hoping to discover a new law, the law of self-organization. This would solve the "problem" of the Second Law, which says that all things naturally decay.

However, if it turns out that this new law really exists, and that the Second Law is not true in every instance, then where would this leave the radioactive dating method? There would no longer be any reason to believe that all substances decay, or that half-lives can actually be calculated.

According to a 1959 college chemistry text, radioactive dating had established (at that time) that the age of the earth's crust was 2.6 billion years, so the earth must be at least that old. Was that date factual? Or is the current date of 4.5 billion years the factual one? Why do up-dated rates always make the earth and the universe older--never younger?

Is radioactive dating rock-solid?

Copyright 2003 Jan Young

Return to Table of Contents

Return to Jan Young--Author