Radiometric dating easy definition
The plot of the ratios of the number of atoms of the parent isotope to the number of atoms in the non-daughter isotope compared to the number of atoms of the daughter isotope to the non-daughter isotope should result in a straight line that intersects the vertical y-axis (which is the ratio of daughter to non-daughter isotopes).This point of intersection gives the initial ratio of daughter to non-daughter isotopes, which would also be the ratio in a mineral that crystallized without any parent isotope present.
On an isochron diagram, this change in ratios shifts each measurement from the sample up and to the left at a one-to-one rate.Thus, the daughter product and any other isotopes of the same element will be incorporated into the minerals of a rock with the same ratio.This initial ratio allows the non-daughter product isotope to be representative of the initial amount of the daughter product (Stassen 1998).Isochron dating bypasses the necessity of knowing the quantity of initial daughter product in the rock by not using that value in the computation.Instead of using the initial quantity of daughter isotope, the ratio of daughter isotope compared to another isotope of the same element (which is not the product of any decay process) is used as the comparison for isochron dating.The steeper the slope of the line, the more decay has occurred in a sample and the older the sample is (Dalrymple 20).
The features of the isochron method provide a way do reduce doubt and speculation about an age that is computed using these methods.
While isochron dates have been used by both old-Earth and young-Earth proponents to promote their respective viewpoints, attacks on isochron dating have also been made by young-Earth creationists, such as William Overn.
These creationists challenge the assumptions made by the isochron dating method itself.
According to Brent Dalrymple (20-69), "the trick to the isochron diagram is the normalization of both parent and daughter isotope to a third isotope." This third isotope is the non-decay product isotope of the same element as the daughter element.
In the initial state, the graph of daughter isotope to the third isotope versus parent isotope to the third isotope should result in a straight, horizontal line.
The first of these assumptions, that all rocks and minerals that formed from the same homogenous mixture have the same age, is not disputed (Overn 2005).