Below is a list of radionuclides (radioactive elements). These are unstable elements that have a tendency to undergo radioactive decay. The list contains every known radionuclide with a half-life longer than 300 years. A half-life is the amount of time it takes for half of a quantity of radioactive material to decay. So, if we start with 1.0 kg of Carbon-14, then after one half life (5,730 years), 0.5 kg of Carbon-14 will remain (and 0.5 kg of the decay product: Nitrogen-14). After another half-life, one half of the remaining Carbon-14 will exist (0.25 kg), and so on. A radionuclide will decay to nearly nothing after about 20 half-lifes. After that amount of time, the amount of radionuclide will be 1 / 2^20 (about one millionth) of it’s original quantity.
The second column of the list says how long the half-life of the element is. The fourth and fifth columns show how many half-lifes would have occurred in 4.5 billion years (the scientific estimate of the age of the earth), and 6,000 years (the age of the earth according to young earth creationists).
(Note to readers: Some of the numbers contain an “E”. This is a scientific notation indicating that you need to move the decimal point to the right to read the value. For example, 7.70E+24 years means “move the decimal point 24 spaces to the right” resulting in a value of 7,700,000,000,000,000,000,000,000 years.)
There are 92 radionuclides on this chart, and they show an interesting pattern. A lot of the radionuclides with long half-lifes exist in nature, but none of the radionuclides with short half-lifes exist. Now, as I mentioned earlier, radionuclides who have existed for more than 20 half-lifes would decay out of existence (at least as far as our being able to detect them). If evolutionists are right in claiming the earth to be 4.5 billion years old, we would expect radionuclides experiencing 20+ half-lifes within 4.5 billion years to have disappeared. (The number of half-lifes within 4.5 billion years can be found in column 4.) Any with longer half-lifes would still be around – assuming they existed on earth in the first place. Looking back at the list, we can see that all long-lived radionuclides exist on earth, and radionuclides with 20+ half-lifes don’t exist on earth with some exceptions.
There are some short-lived radionuclides that can be found on earth which are produced — they are either decay products from long-lived radionuclides, or produced by some continual process. So, it is not surprising that they still exist even in a very old earth:
> Uranium 236 is produced in uranium ores by neutrons from other radioactives.
> Iodine 129 is produced from Tellurium 130 by cosmic-ray muons.
> Manganese 53 and Beryllium 10 are produced by cosmic-ray radiation hitting dust in the upper atmosphere.
> Trace quantities of Np-237 are actually found in nature due to transmutation reactions in uranium ores produced by the neutrons which are present.
> Carbon 14 is produced in the upper atmosphere by radiation from the sun.
> U-234 is a product of U-238 decay (which has a 4.5 billion year half-life).
> Th-230 is a product of U-234 decay.
> Ra-226 is a product of Th-230 decay.
> Cl-36 is produced by cosmic ray interactions with Argon
There is one element in the long list that isn’t continually produced, but has been found despite the fact that would undergo 20+ half-lifes in 4.5 billion years: Pu-244. It has a half-life of 81 million years (i.e. 56 half-lifes within 4.5 billion years).
Finding Plutonium 244. Its half life is 82 million years, so 4.55 billion years is 55 half lives. You might reasonably ask how come Plutonium 244 isn’t listed as no. The answer is that someone made a very serious effort to find it: their article is referenced below. Eighty five kilograms of molybdenum ore were chemically concentrated, and then the lot was tediously run through a mass spectrometer. The amount of Plutonium 244 they found, 10-14 grams, was so small that it would have averaged one single radioactive decay every six years. Clearly, they could not have detected this Plutonium 244 with a geiger counter. However, 55 half lives ago, it would have been about one kilogram of plutonium metal. That’s believable in 85 kilograms of metal ore.
Samarium 146’s half life is 103 million years, so 4.55 billion years is 44 half lives. This means that Samarium 146 could be 200 billion times rarer than Uranium 235, but could be a thousand times commoner than Plutonium 244. I predict that if anyone tries very very hard to find Samarium 146, they will succeed. Curium 247, at almost 300 half lives, is completely out of the question. (Link)
U-235, which appears right above the 20 half-life dividing line, would have gone through 6.39 half-lifes in 4.5 billion years – meaning would decay to 1.2% of the quantity that it existed 4.5 billion years ago. It currently composes only 0.720% of Uranium in nature. This fits well with the expectation that U-235 would be slightly uncommon.
If we assume that the earth is young, the scarcity (but existence) of Pu-244 is a bit peculiar. The young earth hypothesis does not rule out finding minute quantities of Pu-244, but the diminishing abundances of radionuclides as we move through the 1 billion year – 50 million year half-life radionuclides looks peculiar. If the earth was truly only 6,000 years old, it means God created Pu-244 in extremely minute quantities. Had God produced it in larger quantities – quantities comparible to any of the 36 longer-lived radionuclides – then it would be implausible that the earth was very old because it would require that implausibly large amounts of Pu-244 existed 4.5 billion years ago.
So, all the short-lived nuclides which exist on earth are created by some process. There are no short lived radionuclides which exist on earth which are not created by some process on earth. Yet, every long-lived radionuclide exists regardless of whether it is produced on earth or not. This is what we would expect if the earth was old. If the earth is young, we would be surprised by the degree to which this pattern matches the “old earth” hypothesis. Although this pattern is not explicitly ruled out by the young earth hypothesis, the pattern is a quite peculiar.
I chose to list all the radionuclides which have half-lifes of 300+ years for one reason: a half-life of 300 years is exactly 20 half-lifes on a planet that is 6,000 years old. Notice that none of the radionuclides between Nb-92 and Cf-249 exist on earth except for the radionuclides we’ve talked about. There are 43 short-lived radionuclides in that group. If any of them had been present on earth 6,000 years ago “when the earth was created”, they would still exist. But, none of them exist.
One prediction of the old-earth hypothesis is that radionuclides would reach equilibrium with their decay products. For example, Uranium-238 decays into Thorium-234, which decays into Protactinium-234, and so on through a number of different radioactive elements until it turns into Lead-206, which is stable. This is what the U-238 decay chain looks like (starting with Uranium-238 and ending with Lead-206):
This decay chain has the effect of causing radionuclides to exist in specific proportions to each other. In this case, the proportion of U-238 to U-234 is governed by this equation:
Since we know the half-life of U-234 and U-238, we can calculate this value:
245,500 years
——————————— = 0.0000549 (predicted ratio)
4,470,000,000 years
If we look up the relative amounts of U-238 and U-234 in nature, we find that 99.2745% of Uranium on earth exists as U-238, and 0.0055% of Uranium on earth exists as U-234. Thus, the actual ratio of U-234 to U-238 is 0.0055/99.2745 = 0.0000554 (or 0.000055 when we take the number of significant digits into account). The values match – U-238 and U-234 are in equilibrium with each other.
Now, creationists might wonder if this equilibrium can be reached within 6,000 years. This equilibrium cannot be reached in a short amount of time. It takes about 10 half-lifes of the daughter element before they will reach the equilibrium point. 10 half-lifes of U-234 is 2.4 million years. So, the abundance of U-238 and U-234 could not reach equilibrium in 6,000 years.
Other radionuclides in the U-238 decay chain are relatively short lived, so they only exist in minute quantities. We do know that Radon-222 exists, which means that Radium-226 (another radionuclide in the U-238 decay chain) is decaying in significant quantities. Radon-222 is the gas that seeps into basements and causes cancer. The EPA says that it is the second leading cause of lung cancer in the US. The very fact that Radon-222 exists on earth supports the assertion that the entire U-238 decay chain is filled and that requires quite a bit of time (or a deity who creates the earth and radionuclides precisely at their equilibrium points). If the earth is truly 6,000 years old, it means God even created Radon-222, which seeps into basements and causes lung cancers. Maybe He really wanted to make it look authentically old, even if that means causing cancer.
We can also look at other decay products and make predictions about their abundance on earth. We know that U-238 decays through a series of intermediates until it becomes the stable element Lead-206. Since U-238 should’ve gone through about 1 half-life in 4.5 billion years, we can say that half of the original U-238 has become Lead-206. This means that the abundance of Lead-206 be equal to or greater than the amount of U-238 we currently find on earth. In other words, the abundance of Lead-206 which is currently on earth should be = ( the amount of Lead-206 originally on earth ) + ( the amount of Lead -206 that should exist from radioactive decay within 4.5 billion years ). While it is difficult to know how much Lead-206 originally existed on earth, this calculation provides us with an absolute minimum of Lead-206 that should exist. Is there anything here that breaks the old earth theory?
* U-238 (4.47E+09 year half-life) decays into Lead-206. In the lithosphere (the top 25 miles of the earth’s crust), U-238 exists in a ratio of 2.4 ppm (particles per million) and Pb-206 exists in a ratio of 3.3 ppm. Since U-238 has gone through about 1 half life since the formation of the earth, then 2.4 ppm of U-238 should have decayed into Pb-206. Our prediction is confirmed: the abundance of Pb-206 (3.3 ppm) is greater than 2.4 ppm. We can also use the information to put a maximum age on the earth. If Pb-206 exists at 3.3 ppm and U-238 exists at 2.4 ppm, then the U-238 could not have gone through more than 1.25 U-238 half-life, which is 5.6 billion years.
* Th-232 (12 ppm, 1.41E+10 year half-life; 0.32 half-life in 4.5 billion years) decays into Pb-208. Th-232 should’ve produced 3.0 ppm of Pb-208. Pb-208 exists in an abundance of 7.3 ppm.
* Lu-176 (0.013 ppm, 3.78E+10 year half-life; 0.12 half-life in 4.5 billion years) decays into Hf-176. Lu-176 should’ve produced 0.001 ppm of Hf-176. Hf -176 exists in an abundance of 0.17 ppm.
* K-40 (2.457 ppm, 1.28E+9 year half-life; 3.52 half-life in 4.5 billion years) decays into Ca-40 (90%) and Ar-40 (10%). K-40 should’ve produced 16.72 ppm decay products (15 ppm Ca-40, 1.7 ppm Ar-40). Ca-40 exists in an abundance of 39,000 ppm, Ar-40 exists in an abundance of 1.2 ppm. Argon, however, is a gas, and therefore, would escape from the lithosphere into the atmosphere, explaining its low levels there. Argon makes up approximately 1% of the earth’s atmosphere.
* U-235 (0.017 ppm, 7.04E+8 year half-life; 6.39 half-life in 4.5 billion years) decays into Pb-207. U-235 should’ve produced 1.42 ppm of Pb-207. Pb-207 exists in an abundance of 3.08 ppm.
In none of these cases is there insufficient decay product.
The conclusion of all this is that assuming the earth *really is* 4.5 billion years allows you to make amazingly accurate predictions about the radionuclides you’d find on earth and their abundances. If the earth is truly is 6,000 years old, it means God created the earth with radionuclide abundances at precise levels that would match values we’d expect of an old earth, and the fact that you can use the assumption of an old earth to predict abundances of these materials is just an amazing coincidence. (I just can’t help but be reminded of the Pope’s advice to Galileo: that he’s allowed to assume the earth goes around the sun for the purpose of calculating orbits, but he isn’t allowed to claim it’s actually true.)
AnswersInGenesis attempts to answer these types of geological problems for the young earth hypothesis. I found it particularly amusing how they constantly play the “believe God, not man” game. Example:
Superficially, Hayward amasses an impressive battery of arguments as to why the Bible can’t mean what it says. Perhaps the single most important lesson from his book is his strategy itself. Each of his attacks on the Word of God elevates some other ‘authority’, whether derived from geology, astronomy, secular history or theology, above the Bible. This approach is as old as the Garden of Eden. True knowledge begins with the Bible (Proverbs 1:7, Psalms 119:160; 138:2), and that is where we need to start. God was there when He created the world.
– http://www.answersingenesis.org/docs/4127.asp
The only foolproof method for determining the age of something is based on eyewitness reports and a written record. We have both in the Bible. And that is why creationists use the historical evidence in the Bible to constrain their interpretations of the geological evidence.
– http://www.answersingenesis.org/creation/v24/i4/radiometric.asp
I find these answers to be particularly anti-intellectual, and disturbingly flexible. According to their argument, anything that contradicts the Bible is a-priori wrong. Now please disconnect your brains.
Tiny Frog 