The simplest form of isotopic age computation involves substituting three measurements into an equation of four variables, and solving for the fourth.The equation is the one which describes radioactive decay: If one of these assumptions has been violated, the simple computation above yields an incorrect age.Each such age would match the result given by the isochron.Gain or loss of In order to make the figures easy to read (and quick to draw), the examples in this paper include few data points.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).
In addition, it requires that these measurements be taken from several different objects which all formed at the same time from a common pool of materials.
Since the data points have the same Y-value and a range of X-values, they initially fall on a horizontal line: 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.
Isochron methods avoid the problems which can potentially result from both of the above assumptions.
Isochron dating requires a fourth measurement to be taken, which is the amount of a different isotope of the same element as the daughter product of radioactive decay.