Neither internal consistencies, mineral-pair concordances, nor agreements between differing dating methods necessarily validate radiometric dating.
The large spread of values for igneous and metamorphic rocks (especially of the Precambrian) may indicate artificial imposition of time-values upon these rocks.
Finally in 1976, it was discovered that the earth is "really" 4.6 billion years old What happened?
Potassium - Argon and Argon - Argon dating are based on the current understanding that radioactive Potassium-40 decays to the stable form, Argon-40 with a half-life of approximately 1.25 billion years. The conclusions of Renne and his team read as follows: Ar can be identified in volcanic sanidine, and while perhaps negligible in pre-Holocene rocks, it has important consequences for sample at the limit of the methods applicability.
If one starts with an originally pure sample of parent element, then the proportion of parent to daughter tells us the number of half-lives, which has been used to find the supposed age of igneous rocks. Further improvement in precision of Ar dating are most commonly used to "prove" the ancient age of many life forms, I will discuss these dating methods specifically in more detail and show that they, along with the other common methods of isotope dating, are to be highly questioned.
Following the discovery of radioactivity by Becquerel (1896), the possibility of using this phenomenon as a means for determining the age of uranium-bearing minerals was demonstrated by Rutherford (1906).
One year later Boltwood (1907) developed the chemical U-Pb method. By combining Von Weizsackers argon abundance arguments with Kohlhorsters observation that potassium emitted gamma-radiation, Bramley (1937) presented strong evidence that potassium underwent dual decay.