Back to top Radioactive elements decay gradually into other elements.
The original element is called the parent, and the result of the decay process is called the daughter element.
Potassium 40 (K40) decays to argon 40, which is an inert gas, and to calcium.
Potassium is present in most geological materials, making potassium-argon dating highly useful if it really works.
When it is stated that these methods are accurate to one or two percent, it does not mean that the computed age is within one or two percent of the correct age.
It just means that there is enough accuracy in the measurements to compute t to one or two percentage points of accuracy, where t is the time required to obtain the observed ratio of daughter to parent, assuming no initial daughter product was present at the beginning, and no daughter or parent entered or left the system.
In order to use these methods, we have to start out with a system in which no daughter element is present, or else know how much daugher element was present initially so that it can be subtracted out.
We also need to know that no parent or daughter has entered or left the system in the meantime.
Thus radiometric dating methods appear to give evidence that the earth and meteorites are old, if one accepts the fact that decay rates have been constant.
However, there may be other explanations for this apparent age. I also believe that the evidence indicates that the earth has recently undergone a violent catastrophe.
For potassium 40, the half-life is about 1.3 billion years.
In general, in one half-life, half of the parent will have decayed.
If these dates are correct, this calls the Biblical account of a recent creation of life into question.