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.

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.

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.

The amount of initial wouldn't change over time -- because it would have no parent atoms to produce daughter atoms.

It depends on the accuracy of the measurements and the fit of the data to the line in each individual case.) For example, with Rb/Sr isochron dating, any age less than a few tens of millions of years is usually indistinguishable from zero.

That encompasses the entire young-Earth timescale thousands of times over." in the decay equation.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 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.Note that the mere existence of these assumptions do not render the simpler dating methods entirely useless.In many cases, there are independent cues (such as geologic setting or the chemistry of the specimen) which can suggest that such assumptions are entirely reasonable.There are minor differences between isotopes of the same element, and in relatively rare circumstances it is possible to obtain some amount of differentiation between them. The effect is almost always a very small departure from homogeneous distribution of the isotopes -- perhaps enough to introduce an error of 0.002 half-lives in a non-isochron age. but it is rare and the effect is not large enough to account for extremely old ages on supposedly young formations.) as minerals form.

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