Back to the K/Ar system. One complaint often raised by YECs is that there is no guarantee that the mineral being dated has remained a closed system. Such a possibility has been well understood by practitioners. It had to be overcome by those who developed the system in the first place before the technique could be used. If it was not, then scientists in all fields of historical research could not make sense of any date they were given, and the point is that the dates do make sense. They tie in with the pre-existing relative dating systems. They tie in with pre-existing knowledge. Thus, in a relative system, if one stratum was deemed to be older than another, the K/Ar system dates that way as well. If the system was as leaky as YECs make out, then why should that be the case? K/Ar systems also tie in with the pre-existing "absolute" dates. Early geologists did have some idea of the immensity of geologic time and how old some strata could be. K/Ar dating confirmed these notions. K/Ar systems support and are supported by other absolute systems that rely, in the main, on different assumptions. Thus, cross checking can often be performed to ensure the reliability of a date. Again, if the system was as leaky as YECs pretend, it is hard to see how cross checking could be performed. Finally, many YEC suggestions of a leaky system can be checked. Two assumptions often attacked by creationists are -
i) knowledge of the initial daughter and
ii) that the rock remained a closed system.
One way such objections are met is by the use of isochron diagrams. These are constructed from the analysis of several different minerals in a rock where the minerals contain different amounts of parent and daughter isotopes. Ratios of parent and daughter isotopes relative to a third, closely related isotope are used to obtain straight line plots, the slope of which supplies the age of the mineral and the y-intercept, the initial daughter. Hence, the initial daughter quantity is not needed with this method. The linear plot virtually ensures that a closed system has been dated. Problems which can give rise to false isochrons are well known. These problems are rare and certainly do not invalidate the system. Rather they supply dates for subsequent metamorphic events or dates between original rock formation and subsequent metamorphic events. Such dates run into tens of millions of years to hundreds of millions of years.
Compositions of minerals from as wide a variety of sources as possible (e.g. other planetary bodies, various terrestrial locations, etc.), are examined. This is done to ensure that a mineral from one location behaves the same as a mineral from another. If different behaviours are found then this does not invalidate a dating system. Reasons for the behaviours are found. The behaviours are researched and understood, and this new knowledge then places more constraints on the technique. Constraining a method does not make it suspect. Quite naturally it makes it more reliable. This research is not necessarily done as a part of geochronology studies either. Petrologists who wish to understand the nature of rocks undertake such research and obviously it has nothing to do with dating studies. Thus a body of literature was in existence well before radio isotope systems were developed. There was an expertise which physicists could tap into as they developed the absolute dating systems.
How do scientists determine the ability of minerals to retain various elements? There are many books available which describe the extent to which scientists go to determine how various minerals retain elements, under what conditions they can be contaminated, etc. Henry Faul, in his book "Ages of Rocks, Planets, and Stars" describes a lot of this. Consider the loss of argon. Minerals vary greatly in their ability to hold argon. (Hence some will be totally unsuitable for dating purposes and geologists will not use them). An advantage of argon being a gas is that, while it can diffuse through minerals, it is also easy to collect during the dating process. Not only do scientists test minerals for argon retention in the lab, but they test retention in the field as well. In the lab, a mineral is placed in a vacuum and gradually heated. All this time, the argon which has escaped is measured. Some mica's for instance lose very little argon up to a fairly high temperature, then lose a lot, rapidly, until settling down to no loss from then on. Other minerals can be shown to follow a similar pattern. To check these lab tests against reality, scientists go into the field and look for systems where once molten rock has intruded into surrounding cold rock. They can look at the increasing ages of samples taken further from the contact zone and this reinforces and refines laboratory studies.
Petrologists, over the years, have classified rocks and built up an extensive amount of knowledge concerning them – their compositions, physical, chemical, mineralogical; their physical and chemical structures; their properties. Ratios of elements, mineral stabilities, resistances to attack are all known with varying degrees of reliability.
Geologists recognise that rocks, once set, could easily undergo later metamorphic events that interfere with subsequent dating. Tests are done to check for this. For example, metamorphosis is likely to affect different minerals in different ways. Therefore, if different dating systems yield compatible ages, one can be confident that a real age has been determined. Properties of various minerals can be used to see if a rock has undergone metamorphosis. If so, different interpretations have to be placed on an associated date. For example, rather than the date reflecting the time of rock formation, it reflects the time of the last metamorphic event.
Scientists love a chance to test their assumptions using as many independent methods as possible. The reason for this is that scientists really would like to know what is going on in nature. They do want to know the truth. They have no hidden agendas. Conversion of souls is left up to the individual's faith. Eternal life is not tied in with how old a rock is. For that reason, many scientists are theistic including devout Christian and happily accept an ancient Earth as being reality. Therefore, testing of assumptions becomes vital to refining techniques. If the K/Ar system can be extended to other mineral types then its use can be extended. Better quality research can be done and more questions answered. Sometimes one hears YECs claim that modern dating systems were developed to give scientists time for evolution. Such claims are silly. Modern dating systems were developed largely because some people really wanted a good system for dating the earth. It had nothing to do with evolution. As I pointed out earlier, if the mainstream was so dishonest, then there are other dating systems that would put the age of the earth into trillions of years – even better still – and geologists could then use the excuse making that YECs accuse them of to deny the current systems their validity. (Returning to a theme I discussed above – YECs accuse the mainstream of guessing and making excuses. YECs rarely back such assertions up. Nevertheless, reading their literature shows that it is they who deem hand waving and just-so-stories as viable theories. Yet again the mainstream is incorrectly accused of doing precisely what YECs do.)
If scientists are as dishonest as Sarfati suggests, i.e. they make excuses and unsubstantiated assertions then why be limited in dishonesty when it comes to dating? By this I mean, why not claim to be able to date everything? However, the literature shows that only some things can be dated. For example, Dalrymple's book on the K/Ar system has a chapter titled "What can be dated?" Out of all possibilities only a few of the rock forming minerals can be dated. Some of these can only be dated under exceptional circumstances. Thus, biotite, a mica, can be dated in volcanic, plutonic and metamorphic rocks; lepidolite can only be dated sometimes, in plutonic rocks. Sedimentary rocks are very hard to date. The mica, glauconite, offers the only chance there. The reason for all this is that only some things are understood well enough so that scientists are confident or otherwise in the usefulness of the mineral and the technique applied to it in order to extract a date. As an example, biotite retains argon well. However, if heated above a few hundred degrees Centigrade, the mineral easily loses argon. Because of this though, the mineral, while good for providing rock formation ages, is also very useful for indicating post formation heating events. Under this scenario, a date of 50,000,000 years would not be the age of the rock. Rather it would be the age since the rock was last heated to above a few hundred degrees. And this would have to be less than the age of the rock! Quartz though is different. While it retains argon well it has a very low potassium content which makes its usefulness very limited. Understand the system and it can be used. If geologists and physicists adopted the YEC scientific method, then the mainstream could claim that everything can be dated and use statements such as "God would have" and "God could have" to answer any objections that the associated dates were based on unknown, untested and unscientific methodologies. Unless such statements are based on real knowledge of God's intentions, then really, they are all unsubstantiated assertions and as such just one of many things God could have or would have done.
It is important to see what is being suggested by YECs when they raise their objections.
1) When you read YEC literature, the impression is made that geologists are being untruthful or are blind. Either they know that the systems are leaky and ignore it or they are blissfully unaware of the potential for error. Nothing could be further from the truth. Reading the historical literature on this, you will see that scientists always raised objections to dating systems that they considered unreliable. Such dating systems could be used – but only as a last resort, in the absence of anything better. In order to develop the modern systems, something had to be offered that could answer the objections to the older systems. From the literature it is also clear that scientists love to check and cross check their systems. Thus, when tree ring dating systems matured, they were used to check the carbon 14 dating system. And sure enough, as the carbon dates went back in time, so their accuracy began to decline. The sources of these small inaccuracies are now understood and tree rings have been used to re-calibrate the carbon clock. (And the earth sure ain't 6,000 years old.)
2) In challenging the mainstream, YECs rarely mention their own assumptions and with good reason. Often their assumptions are groundless, cases of special pleading or contrivances. YEC critiques of an ancient Earth rely on the assumption that all dating techniques must fail in a methodological way so that any age above 6,000 years, no matter how well established, can be discounted. Assumptions behind their special pleading are rarely stated and never supported. They are merely hand waved into the story. Thus, Woodmorappe (below) can assume that decay in an ionised state is relevant to modern dating systems by assuming that God behaved in a particular way at creation, to ensure that rocks had the right amount of elements (but not all rocks mind you) so that geologists could be misled. Not only does Woodmorappe assume this for one dating system but the implication is, (and why not?) that God tweaked all other dating systems as well – but in different ways.
... It isn't the "evidence" that is in dispute. It is the explanation of the evidence.