Age Dating - Creationist Links
However, in the very principal of radiometric dating there are several vital . attacks on isochron dating have also been made by young-Earth creationists, such Not Billions: Challenging an Icon of Evolution, Questioning the Age of the Earth. Or are creationists guilty of 'cherry picking'? . Radiometric back flips; How solid are those dates? (Creation . Evolution's Achilles' Heels DVD. A brief introduction to isochron dating methodology. The technique The Talk. Origins Archive: Exploring the Creation/Evolution Controversy.
If some of the radiogenic argon has escaped, then more K40 must have decayed than we think -- enough to produce what we did find plus what escaped. In other words, a mineral that has lost argon will be older than the result we get says it is.
In the other direction, if excess argon has gotten into the mineral, it will be younger than the result we get says it is.
Evidences of a Recent Creation
An isochron dating method isochron dating is described in the next section can also be applied to potassium-argon dating under certain very specific circumstances. When isochron dating can be used, the result is a much more accurate date. Yet a fourth method, rubidium-strontium dating, is even better than potassium-argon dating for old rocks. The nuclide rubidium Rb87 decays to strontium Sr87 with a half-life of 47 billion years.
Strontium occurs naturally as a mixture of several nuclides. If three minerals form at the same time in different regions of a magma chamber, they will have identical ratios of the different strontium nuclides. The total amount of strontium might be different in the different minerals, but the ratios will be the same. Now, suppose that one mineral has a lot of Rb87, another has very little, and the third has an in-between amount. That means that when the minerals crystallize there is a fixed ratio of Rb As time goes on, atoms of Rb87 decay to Sr, resulting in a change in the Rb Sr87 ratio, and also in a change in the ratio of Sr87 to other nuclides of strontium.
The decrease in the Rb Sr87 ratio is exactly matched by the gain of Sr87 in the strontium-nuclide ratio. It has to be -- the two sides of the equation must balance. If we plot the change in the two ratios for these three minerals, the resulting graph comes out as a straight line with an ascending slope.
This line is called an isochron. When every one of four or five different minerals from the same igneous formation matches the isochron perfectly, it can safely be said that the isochron is correct beyond a reasonable doubt.
There are numerous other radiometric dating methods: A full cite for this book is given in the bibliography. Possible Sources of Error Now, why is all this relevant to the creation-vs. Every method of radiometric dating ever used points to an ancient age for the Earth. For creationists to destroy the old-Earth theory, they must destroy the credibility of radiometric dating.
They have two ways to do this. They can criticize the science that radiometric dating is based on, or they can claim sloppy technique and experimental error in the laboratory analyses of radioactivity levels and nuclide ratios.
Criticize the Theory Is there any way to criticize the theory of radiometric dating? Well, look back at the axioms of radiometric dating methods. Are any of those open to question. Or at least, they seem to be. Do we know, for a fact, that half-lives are constant axiom 1?
Do we know for a fact that nuclide ratios are constant axiom 2? Regarding the first question: However, if all we had were theoretical reasons for believing axiom 1, we would be right to be suspicious of it.
Do we have observational evidence? On several occasions, astronomers have been able to analyze the radiation produced by supernovas. In a supernova, the vast amount of energy released creates every known nuclide via atomic fusion and fission. Some of these nuclides are radioactive. We can also detect the characteristic radiation signatures of radioactive decay in those nuclides.
We can use that information to calculate the half-lives of those nuclides. In every case where this has been done, the measured radiation intensity and the calculated half-life of the nuclide from the supernova matches extremely well with measurements of that nuclide made here on Earth. And when we look at a supernova in the Andromeda Galaxy, 2, years old, we see nuclides with the exact same half-lives as we see here on Earth.
Not just one or two nuclides, but many. For these measurements to all be consistently wrong in exactly the same way, most scientists feel, is beyond the realm of possibility. What about nuclide ratios?
- Creation Science Explained
- Isochron Dating
- Age Dating Links
Are they indeed constant? Minerals form by recognized chemical processes that depend on the chemical activity of the elements involved. The chemical behavior of an element depends on its size and the number of electrons in its outer shell. This results in a range of X-values for the data points representing individual minerals. Since the data points have the same Y-value and a range of X-values, they initially fall on a horizontal line: Differential migration of elements as minerals form.
A horizontal line represents "zero age. In most cases, any age less than about P half-lives will include zero within its range of uncertainty. The range of uncertainty varies, and may be as much as an order of magnitude different from the approximate value above.
It depends on the accuracy of the measurements and the fit of the data to the line in each individual case. That encompasses the entire young-Earth timescale thousands of times over. As more time passes and a significant amount of radioactive decay occurs, the quantity of P decreases by a noticeable amount in each sample, while the quantity of D increases by the same amount.
This results in a movement of the data points to the left decreasing P and upwards increasing D. Since each atom of P decays to one atom of D, the data point for each sample will move along a path with a slope of As a result, the data points with the most P the right-most ones on the plot move the greatest distance per unit time. The data points remain colinear as time passes, but the slope of the line increases: Movement of data points as decay occurs.
The slope of the line is the ratio of enriched D to remaining P. Miscellaneous notes Age "uncertainty" When a "simple" dating method is performed, the result is a single number. There is no good way to tell how close the computed result is likely to be to the actual age.
An additional nice feature of isochron ages is that an "uncertainty" in the age is automatically computed from the fit of the data to a line.Why Earth Is Old, Without Radiometric Dating, YEC Debunked - Stuart Robbins
A routine statistical operation on the set of data yields both a slope of the best-fit line an age and a variance in the slope an uncertainty in the age. The better the fit of the data to the line, the lower the uncertainty. For further information on fitting of lines to data also known as regression analysissee: Yorka short technical overview of a technique specially designed for assessing isochron fits.
Note that the methods used by isotope geologists as described by York are much more complicated than those described by Gonick. This will be discussed in more detail in the section on Gill's paper below. The "generic" method described by Gonick is easier to understand, but it does not handle such necessities as: Unfortunately, one must wade through some hefty math in order to understand the procedures used to fit isochron lines to data.
General comments on "dating assumptions" All radiometric dating methods require, in order to produce accurate ages, certain initial conditions and lack of contamination over time. The wonderful property of isochron methods is: This topic will be discussed in much more detail below.
Where the simple methods will produce an incorrect age, isochron methods will generally indicate the unsuitability of the object for dating. Avoidance of generic dating's problems Now that the mechanics of plotting an isochron have been described, we will discuss the potential problems of the "simple" dating method with respect to isochron methods. Initial daughter product The amount of initial D is not required or assumed to be zero. The greater the initial D-to-Di ratio, the further the initial horizontal line sits above the X-axis.
But the computed age is not affected. If one of the samples happened to contain no P it would plot where the isochron line intercepts the Y-axisthen its quantity of D wouldn't change over time -- because it would have no parent atoms to produce daughter atoms. Whether there's a data point on the Y-axis or not, the Y-intercept of the line doesn't change as the slope of the isochron line does as shown in Figure 5.
Therefore, the Y-intercept of the isochron line gives the initial global ratio of D to Di. For each sample, it would be possible to measure the amount of the Di, and using the ratio identified by the Y-intercept of the isochron plot calculate the amount of D that was present when the sample formed. That quantity of D could be subtracted out of each sample, and it would then be possible to derive a simple age by the equation introduced in the first section of this document for each sample.
Each such age would match the result given by the isochron. Contamination - parent isotope Gain or loss of P changes the X-values of the data points: Gain or loss of P.
In order to make the figures easy to read and quick to drawthe examples in this paper include few data points. While isochrons are performed with that few data points, the best ones include a larger quantity of data. If the isochron line has a distinctly non-zero slope, and a fairly large number of data points, the nearly inevitable result of contamination failure of the system to remain closed will be that the fit of the data to a line will be destroyed.
For example, consider an event which removes P. The data points will tend to move varying distances, for the different minerals will have varying resistance to loss of P, as well as varying levels of Di: Loss of P in all samples The end result is that the data are nearly certain not to remain colinear: Loss of P destroys the fit to a line. Even in our simple four-data-point example isochron, a change to two of the samples Migration of parent in two data points.
Specific loss of P required to yield a different colinear plot. The two samples must each change by the indicated amount -- no more and no less -- if the data are to remain colinear. In the special case where the isochron line has a zero slope indicating zero agethen gain or loss of P may move the data points, but they will all still fall on the same horizontal line.
In other words, random gain or loss of P does not affect a zero-age isochron. This is an important point. If the Earth were as young as young-Earth creationists insist, then the "contamination" which they suggest to invalidate dating methods would have no noticeable effect on the results.
Moreover, the daughter atoms produced by decay in a mineral are isotopes of different elements and have different ionic charges and radii compared with their parents. The energy released during the decay may produce dislocations or even destroy the crystal lattice locally, thus making it all the more easy for the radiogenic daughters to escape. This will change the vertical position of the data points: Gain or loss of D.
As with gain or loss of P, in the general case it is highly unlikely that the result will be an isochron with colinear data points: Exceptions for loss of daughter There are two exceptions, where it is possible for migration of D to result in an isochron with reasonably colinear data points: If the D is completely homogenized, then the isochron age is reset to zero. When this happens, any later dating attempt will yield the age of that metamorphic event rather than the original time of crystallization: Complete homogenization of radiogenic daughter resets the isochron age to zero.
If the D is partially homogenized in a reasonably regular manner, the isochron age can be partially reset and the samples will date to sometime in between the original time of crystallization and the time of metamorphism.
This is a very rare occurrence, but examples are known: Partial homogenization of radiogenic daughter in some exceptional cases results in an apparently valid isochron of reduced age. These exceptions should be of little comfort to young-Earthers, for 1 they are uncommon extremely uncommon in the case of partial resetting ; and 2 the result in both cases is an isochron age which is too young to represent the time of formation.
Young-Earthers necessarily insist that all ancient isochron ages are really much too old. So, are isochron methods foolproof? In the real world, nothing is perfect. There are some isochron results which are obviously incorrect.