In the 1860's, English physicist Lord Kelvin disagreed with Charles Lyells proposition that the earth behaves in a uniform, unchanging manner.Prior to 1905 the best and most accepted age of the Earth was that proposed by Lord Kelvin based on the amount of time necessary for the Earth to cool to its present temperature from a completely liquid state.We can see how do deal with this if we take a particular case. For example the amount of Rb in mantle rocks is generally low, i.e. The mantle thus has a low If these two independent dates are the same, we say they are concordant.Certain naturally occurring radioactive isotopes are unstable: Their nucleus breaks apart, undergoing nuclear decay.Sometimes the product of that nuclear decay is unstable itself and undergoes nuclear decay, too.For example, when U-238 (one of the radioactive isotopes of uranium) initially decays, it produces Th-234, which decays to Pa-234.n-radiogenic origin incorporated into a mineral during its initial formation, in subsequent recrystallization processes or by contamination during analysis.As the presence of even small amounts of unsupported lead in a zircon or other datable mineral will increase its apparent U-Th-Pb ages, the presence of uncetected or uncorrected common lead is very detrimental to U-Pb dating.
Gaseous and liquid states: Absolute scale of temperature, ideal gas equation; Deviation from ideality, van der Waals equation; Kinetic theory of gases, average, root mean square and most probable velocities and their relation with temperature; Law of partial pressures; Vapour pressure; Diffusion of gases.
Buffon's Iron Sphere Experiments- On the basis of iron sphere cooling experiments, Frenchman Georges de Buffon estimated that the Earth would have needed 75,000 years to cool to its present temperature.
The quantitative approach is admirable, but Buffon's assumptions are flawed. Silicate minerals have lower heat conductivity than steels and are better insulators leading to slower cooling rates.
Second, the calculations did not incorporate the heating effects of radioactive decay.
Strata Thickness- In the late 1800s, a British geologist estimated that 75 million years has lapsed since the beginning of the Cambrian.