Stunning Evidence for Accelerated Radioactive Decay
Radioactive decay occurs when unstable atoms give off energy called radiation. For example, uranium-238 gives off energy and converts into thorium-234. Radiation takes place when an unstable nucleus tries to become stable by means of alpha-decay, beta-decay, or gamma-decay.
An alpha particle consists of two protons and two neutrons and usually is written as α in equations. It is identical to a helium nucleus since it has the same atomic number — two protons. Therefore, it can also be written as 42He (where the ‘4’ in superscript denotes the mass and the ‘2’ in subscript denotes the atomic number or number of protons).
An alpha emission reduces the atom’s atomic number by two (since the emitted alpha particle contains two protons) and reduces the mass by four (since the emitted particle contains two protons and two neutrons). For example, an alpha emission from uranium-238 (23892U) would change it to thorium-234 (23490Th). Note the corresponding changes in mass number and atomic number.
Alpha decay can be quite dangerous only when ingested, but is otherwise relatively harmless since it can be effectively shielded by paper, a few centimetres of air, or a layer of dead skin cells.
Beta decay occurs when an atom emits beta-particles (represented as β in equations) which are either high-speed electrons or positrons. Beta decay by electron emission is denoted by β−while positron emission is denoted by β+.
Electron emission (β−) occurs when a neutron of an unstable atomic nucleus converts into a proton, an electron (the beta particle), and an electron-type antineutrino. β− happens when the nucleus contains excess neutrons.
Positron emission (β+) occurs when a proton converts into a neutron, a positron (the beta particle), and an electron-type neutrino. β+happens when the nucleus contains excess protons.
Beta particles can be used to treat bone and eye cancer and to test the thickness of paper during manufacturing.
Gamma decay takes place when an atom emits a photon to decrease the very high energy of the nucleus. This sometimes occurs in conjunction with alpha or beta decay. The symbol denoting a gamma ray is written asγ. Gamma rays do not affect the atomic number or mass number of an atom since they themselves do not have significant mass. A very thick barrier must be in place to shield the rays effectively, such as a concrete wall.
The half-life of a radioactive element describes the length of time needed for half of the amount of radioactive atoms in a sample to decay. For example, the half-life for carbon-14 is 5,730 years. Now suppose we have one hundred carbon-14 atoms in a sample; after 5,730 years (one half-life) only fifty will remain, with the other fifty being lost to decay.
Now after 11,460 years (two half-lives), the amount of carbon-14 atoms in the sample will not be zero. Rather, it will be a halving of the remaining carbon-14 atoms. This means that one quarter of the original carbon-14 will be present. After three half-lives, one eighth will remain. After four half-lives, one sixteenth will remain. And so on.
The accuracy of half-lives is based on a number of tests, but no half-life is absolutely precise. Scientists did not wait around for 5,730 years to make sure that the carbon-14 half-life really is 5,730 years! The problems may escalate with larger half-lives, such as that of uranium-238 which has (supposedly) a half-life of 4.4 billion years. There is now good evidence that the half-lives of some elements, such as uranium, were seriously shorter in the past (i.e. the radioactive decay rate was sped up).
Accelerated Radioactive Decay
We know for a fact that the decay rates of elements such as beryllium and rhenium are not constant. Also, the RATE team (Radioisotopes and the Age of the Earth) has provided startling evidence for a much higher decay rate of elements such as uranium.
Beryllium to Lithium
Beryllium-7 decays to lithium-7 by a decay method called electron capture. Electron capture can be compared with β+ decay because a proton captures an electron and converts into a neutron. An electron-neutrino is released in this process. We now know that different chemical forms of beryllium-7 decay into lithium-7 where the decay rate varies by 1.5%. The measured half-lives range from 53.69 days to 53.42 days to 54.23 days.
Perhaps the most popular radioactive decay method, potassium-40 to argon-40, occurs by electron capture. Could this, too, have varying decay rates?
Rhenium to Osmium
A version of beta decay called bound-state beta decay happens when a β– particle escapes from a fully ionized atom and enters an unoccupied electron orbital. This type of beta decay is denoted like so: βb.
Now rhenium-187 usually decays to osmium-187 with a half-life of 42 billion years. However, fully ionized rhenium-187 atoms were observed to decay with a half-life of only 33 years. The two rates differ by a factor of one billion!
Radiation can cause damage to atomic arrangement that looks to the eye like discolouration. Such discolouration exists in many of Earth’s granites, showing that radioactive decay must have occurred during the rock’s past. Now this discolouration is in the form of spherical shells — much like the layers of an onion — with the radiation-causing uranium particle residing in the centre of the ‘onion’. This centre is called a radiocenter, while the ‘onion’ itself is called a radiohalo.
Scientists can determine what type of radioactive element caused the radiohalos by studying the rings present. They noticed something very interesting: there are radiohalos with rings that were caused by polonium only. Rings from other elements such as uranium are not present. This is most unusual because polonium is a product of uranium decay (see Table 1). If polonium rings exist, then uranium, thorium, and a whole host of other rings should also exist in the radiohalo. This is not the case in some examples. How can this be?
|Uranium-238||α||4.47 billion years|
Andrew Snelling has proposed a reasonable hypothesis whereby polonium, produced by the decay of a normal uranium radiohalo, was transported by water outside the uranium radiohalo to a new place in the rock. There, it formed its own radiohalo having only polonium rings. This ‘polonium only’ radiohalo is called a parentless radiohalo, since no parent uranium rings exist (or any rings from other elements for that matter).
For a visible uranium radiohalo to form, uranium must emit 500 million alpha particles. At present rates, this would take about 100 million years. By deduction, every visible radiohalo must be at least 100 million years old. But here we run into a problem.
Polonium has a very short existence. Polonium-210 has a half-life of about 138 days; polonium-214 has one of 164 microseconds, and polonium-218 one of three minutes. Now the formation of parentless polonium radiohalos requires a large amount of polonium, otherwise the polonium present would all decay away too quickly and there would be no radiohalo. This large amount of polonium is equal to 100 million years worth of uranium decay.
So, uranium had to decay for 100 million years in order to create the required amount of polonium needed to make a parentless polonium radiohalo. And here’s the problem: after 100 million years, the polonium already produced would have decayed away before a radiohalo could be made! This means that uranium decay must have been much, much faster in order to produce the required amount of polonium all ‘at once’ before it quickly decays away.
Polonium radiohalos show that uranium decay must have been up to a billion times faster than today! And because many other dating methods are calibrated with the uranium method, they too would be inaccurate.
Helium Diffusion in Zircons
As shown in Table 1, many elements in the uranium-238 decay chain emit alpha particles. Because alpha particles are a type of helium, the decay of uranium-238 to lead-206 produces helium as a by-product. Now helium is a very ‘slippery’ molecule since it is in constant motion, does not chemically react, and is small. It should escape rock quite easily.
Studies on supposedly 1.5 billion year-old zircon crystal have shown that they contain too much helium(which is made up of alpha particles and 2 electrons). Up to 58% of the helium produced over the supposed 1.5 billion years still exists in the zircon crystal. According with known leakage rates, this puts the age of the granites at 5,680 years (± 2,000). This is startling evidence of not only a young Earth, but also a much faster decay rate of the uranium-238 chain. Proponents of an old Earth must suggest a helium leakage rate that is 100,000 times slower than measured today to explain the large helium retention. This is highly unlikely; especially since heating of the rock, which is thought to have happened many times,speeds up leakage.
If uranium-238 in zircon crystals really did decay over 1.5 billion years (as believers in an old Earth tell us) the helium should have largely leaked out long ago. This indicates that the decay rate of uranium was greatly sped up, with 1.5 billion years’ worth occurring in just a few thousand years.
The Heat Problem
Now, there is a problem with greatly sped up decay rates. Since heat is produced during radioactive decay, much faster decay rates (as needed for a young Earth) mean the Earth’s crust would be molten. Some scientists have proposed that a stretching of space itself would allow the large amounts of heat to dissipate into the fabric of space.
Even if this model does not explain how the excess heat could dissipate, that would not be the end of accelerated radioactive decay. Jonathan Sarfati explains: “Many scientists have discovered the existence of a phenomenon long before anyone could explain how it occurred.” Indeed, Isaac Newton established the existence of gravity long before anyone was able to properly explain it.
In our case, the evidence for accelerated radioactive decay is in observation, radiohalos, and the helium in zircons and must take precedence over any possible difficulties.
The evidence for accelerated radioactive decay is quite astounding, and explains how the Earth could be only thousands of years old where many radioactive dates of billions of years are obtained. Young Earth creationists do not have to leave their brains at the church door!
- Huh, C.-A., “Dependence of the decay rate of 7Be on chemical forms,” Earth and Planetary Science Letters 171:325–328, 1999. Back to text
- Faure, G., Principles of Isotope Geology (John Wiley & Sons, New York, 1986), 2nd edition, p. 30. Back to text
- Bosch, F. et al., Observation of bound-state β– decay of fully ionized 187Re, Physical Review Letters 77(26):5190–5193, 1996; Kienle, P., Beta-decay experiments and astrophysical implications, in: Prantzos, N. and Harissopulus, S., Proceedings, Nuclei in the Cosmos, pp. 181–186, 1999. Back to text
- Moazed, C., R. M. Spector, and R. F. Ward, “Polonium radiohalos: An alternative interpretation,” Science 180:1272–1274, 1973. Back to text
- Sarfati, Jonathan, The Greatest Hoax on Earth? Refuting Dawkins on evolution (Creation Book Publishers, Atlanta, Georgia, 2010), p. 189. Back to text