Polonium Halos as a Creationist Clock

By Scott Pfahler

General Overview

In order to find an age for the Earth, scientists and (more recently) creationists have looked to the field of geology to find answers. Both proponents of an old Earth and proponents of a young Earth have used characteristics of rocks to justify their theories. One recent theory currently being used as evidence of a young Earth involves what are known as pleochroic halos. Pleochroic halos occur in certain types of igneous rock such as granite that contain minerals such as zircon and monazite, which can be inclusions within other minerals such as mica. It is known that the crystal lattice of these minerals commonly contains traces of certain radioactive elements. These radioactive materials can leave radiation damage in the form of discoloration in the surrounding rock. This radiation damage or "halo" appears as a fuzzy spherical shaped discoloration in the mineral structure emanating from the location of the radioactive material (as seen in figure 1). Creationists and young earth proponents use a specific type of pleochroic halo, purported to be caused by the radioactive element polonium, to make the claim that the Earth could not be billions of years old, but must be much younger. It is important to note, however, that polonium halos do not give any specific age of the Earth and young Earth supporters are not attempting to use them as a dating method. Instead, polonium halos are seen as a way to discount scientists' claims that the Earth has a geologic record which took billions of years to form. In short, polonium halos are not natural clocks because they cannot be said to give any specific age, but creationists infer certain things about these halos that they say are evidence of a young Earth.

pyroxene halos

A typical example of pleochroic halos found here in zircon inclusions of pyroxene.

Creationists' take on Polonium halos

The originator of the polonium halo theory as evidence for a young Earth is the physicist Robert V. Gentry. He believes that he has found evidence in pleochroic halos of granites that indicate that the Earth cannot have been formed over millions or billions of years, but must have been created in a short amount of time, in keeping with the Genesis account of creation. Gentry claims that halos such as the one in figure 2 were caused by traces of the element polonium in primordial granite (i.e. granite from the early origins of the Earth). He believes that because of polonium's remarkably short half-life, (sometimes just microseconds long) there is no way that these granites could have formed through millions of years of cooling as geologists commonly claim, but instead must have formed nearly instantaneously, as by some supernatural power.

radiation damaged biotite halos

Radiation damage halos in biotite mica used by Robert Gentry to support a young Earth.

Gentry's theory makes the following assumptions about the halos he observed:

The basic point of Gentry's research is not to provide a specific date for the formation of the Earth, as polonium halos do not work well as a natural clock. Instead, it seems that Gentry's intentions are to throw the proverbial "monkey wrench" into the traditional scientific model for Earth's formation. If the above assumptions are correct, Gentry asserts that the granites in which the proposed polonium halos were found cannot have been formed over millions or billions of years, but must have been formed in a relatively short amount of time because of the relatively short half-life of polonium. There is absolutely no indication in Gentry's research of exactly when this proposed rapid formation of primordial granite took place, only that it happened quickly. And so, if the formation of the primordial rocks of the Earth's crust did not take billions of years, then to Gentry this seems to make a young Earth more plausible. In short, Gentry's polonium halo research is not direct evidence of a young Earth, but indirect evidence. As will be shown below, however, even this indirect evidence of a young Earth may not hold up to scrutiny ("Fingerprints of Creation" 2005).

Scientific criticisms of Gentry's theory

Scientists such as Tom Baillieul and John Brawley have done research and published articles refuting Gentry's theory of polonium halos. John Brawley is an amateur scientist who published an article about research he conducted which concludes that there are other radioactive materials that form halos which are indiscernible from polonium halos, making it impossible to tell whether or not the halos that Gentry studied are indeed formed by polonium (Brawley 1992). Baillieul refutes Gentry's claims by examining his assumptions about the halos that he observed. Baillieul claims that the assumption that the rock which these supposed polonium halos were found is primordial is not true. As Baillieul explains, Gentry is a physicist, not a geologist, and as a result he is not able to properly put the rocks being examined in their proper context. Gentry's samples were sent to him by colleagues from around the world, so he cannot be entirely sure how they fit into the geological time scale. Baillieul asserts that the types of granite that Gentry uses are not actually primordial, and that some of them are not even granite as Gentry claims. Baillieul then challenges Gentry's assumption that the particular ring-shaped halos that he observed can be positively identified as the result of alpha particle bombardment. Gentry bases this assumption on past research done at a time when the structure of the atom was just being discovered. Baillieul believes that that there are still some unanswered questions about being able to positively identify the type of radiation that caused a halo based on properties like the ring structure and color of the halos. He believes that for this reason the assumption that the observed halos are caused by alpha particle bombardment is at best speculative. Finally, Baillieul claims that even if it is assumed that the halos are cause by alpha radiation, that it seems more likely that the halos would have been caused by the decay of Radon 222. Radon 222 decays to Polonium 218, and is also part of the decay series of Uranium 238. Since Uranium 238 has half-life of approximately 4.5 billion years and can constantly supply a rock with Polonium, there is no reason to assume that the rock must have formed quickly or be "primordial." Baillieul claims that because Gentry's assumptions do not hold up to scrutiny, polonium halos do not provide adequate evidence to support the theory of a young Earth (Baillieul 2005).

Findings of the Rate Project

A recent book titled Thousands.Not Billions which touts a young Earth provides a more recent creationist view on polonium halos. This research, which was conducted by the RATE project, claims to carry on Gentry's work on radiohalos, but in fact seems only to cause more confusion. The RATE team does not believe that polonium halos are evidence of an instantaneous supernatural creation of primordial rocks. Instead, they claim that polonium halos are evidence that at one point in Earth's history, nuclear decay was accelerated. To reach this conclusion, RATE scientists examined rocks from the Precambrian, Paleo-Mesozoic, and Tertiary periods for presence of polonium halos. They discovered that very few halos were found in all periods except for the Paleo-Mesozoic. They concluded that this spike in polonium halos was congruent with the Noadic flood and indicated an increased rate of nuclear decay. In essence, the RATE team is trying to use polonium halos not as a dating method, but to discredit a dating method. Another claim that the rate team makes is in regards to what they call "parentless radiohalos." Parentless radiohalos are halos that appear without any "parent" Uranium atoms. The RATE team offers several different ways that these halos could have formed, including through hydrothermal transport of polonium during the formation of the rock. They believe that this is evidence of rapid cooling of the magma which formed these rocks instead of the long periods of time that are generally accepted. The problem with the RATE data is that it seems to be completely inconsistent with the findings of Gentry, and only seems to further confuse the matter of polonium halos. The RATE data jumps from using polonium halos strictly as a way to discount radiometric dating to attempting to show that certain rocks cooled over a short as opposed to a long period of time. In short, it is not easy to pin down what exactly the point of the RATE research on polonium halos is. It is not conclusive, and is not congruent with the findings of Robert Gentry, on which it was supposedly based (DeYoung 2005:82-97).


Research by scientists such as Baillieul asserts that the polonium halo theory is not at the moment strong enough to form any convincing argument for a young Earth. At the very least, the questions raised by Baillieul need to be fully addressed for the polonium halo theory to carry any weight. The assertion that polonium halos are evidence of a young Earth seems problematic. Polonium halos do not give any idea as to the age of the Earth, rather they are evidence (and weak unverified evidence at best) that specific types of granite can not have formed over long periods of time. It seems that creationists still have a long ways to go before they can provide conclusive evidence of a young Earth, and polonium halos do not seem to be getting them there.

  1. Baillieul, Thomas A. "'Polonium Haloes' Refuted." Talk Origins Archive. http://www.talkorigins.org/faqs/po-halos/gentry.html. Last Updated April 22, 2005. Accessed: November 14, 2005.
  2. Brawley, John. "Evolution's Tiny Violences: the Po-Halo Mystery." Talk Origins Archive. http://www.talkorigins.org/faqs/po-halos/violences.html Last Updated: December 22, 1992. Accessed: November 14, 2005.
  3. Earth Science Associates. "Fingerprints of Creation." http://www.halos.com. Last Updated: 2005. Accessed, November 14, 2005.
  4. Gentry, Robert V. Creation's Tiny Mystery. Earth Science Association, 2003.
  5. DeYoung, Don. 2005. Thousands.Not Billions. 82-97.