Relative dating of fossils is based on what
This estimate was actually reduced over his lifetime to between 20 Ma and 40 Ma and eventually to less than 10 Ma. Perry, in particular, a noted physicists and former assistant to Kelvin, showed that cooling calculations using different but equally likely assumptions and data resulted in ages for the Earth of as much as 29 Ga.
Other factors and basic assumptions must also be considered.What is especially telling about this whole story is the conclusion of the absolute truth of the conclusion based on premises that are weak, or at least not adequately demonstrated.Chamberlain (1899) pointed out that Kelvin's calculations were only as good as the assumptions on which they were based.The isochron dating method theoretically overcomes the need to know the initial ratio of parent and daughter isotopes. For now, we will look at those methods that do fall under the above assumptions.Interweaving the relative time scale with the atomic time scale poses certain problems because only certain types of rocks, chiefly the igneous variety, can be dated directly by radiometric methods; but these rocks do not ordinarily contain fossils.Most sedimentary rocks such as sandstone, limestone, and shale (which do contain fossils) are related to the radiometric time scale by bracketing them within time zones that are determined by dating appropriately selected igneous rocks in lava flows, or weathered from lava flows.
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 solar estimate was based on the idea that the energy supply for the solar radioactive flux is gravitational contraction.
These two independent and agreeing dating methods for of the age of two primary members of the solar system formed a strong case for the correctness of his answer within the scientific community.
It was based on the idea that no significant source of novel heat energy was affecting the Earth.
He believed this even though he did admit that some heat might be generated by the tidal forces or by chemical action.
One year later Boltwood (1907) developed the chemical U-Pb method. By combining Von Weizsacker’s argon abundance arguments with Kohlhorster’s observation that potassium emitted gamma-radiation, Bramley (1937) presented strong evidence that potassium underwent dual decay.