Himalayas 10 times younger than previously thought? History of Radiometric Dating. The radioactivity of Potassium 40 is unusual, in that two processes take place: At the time that Darwin's On the Origin of Species was published, the earth was "scientifically" determined to be million years old. Byit was found to be 1. Inscience firmly established that the earth was 3. Finally init was discovered that the earth is "really" 4.
The study of geology grew out of field studies associated with mining and engineering during the sixteenth to nineteenth centuries. In these Potassium-argon dating accuracy international magazines studies the order of sedimentary rocks and structures were used to date geologic time periods and events in a relative way.
At first, the use of "key" diagnostic fossils was used to compare different areas of the geologic column. Although there were attempts to relative age estimates, no direct dating method was available until the twentieth century.
However, before this time some very popular indirect methods were available. For example, Lord Kelvin had estimated the ages of both the Earth and the Sun based on cooling rates.
The answer of 25 million years deduced by Kelvin was not received favorably by geologists. Both the physical geologists and paleontologists could point to evidence that much more time was needed to produce what they saw in the stratigraphic and fossil records. As one answer to his critics, Kelvin produced a completely independent estimate -- this time for the age of the Sun. His result was in Potassium-argon dating accuracy international magazines agreement with his estimate of the age of the earth.
The Potassium-argon dating accuracy international magazines 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. This just goes to show that just because independent estimates of age seem to agree with each other doesn't mean that they're correct - despite the fact that this particular argument is the very same one used to support the validity of radiometric dating today.
Other factors and basic assumptions must also be considered. Without this knowledge, he argued that, "As for the future, we may say, with equal certainty, that inhabitants of the Earth cannot continue to enjoy the light and heat essential to their life, for many million years longer, unless sources now unknown to us are prepared in the Potassium-argon dating accuracy international magazines storehouse of creation.
There were indeed powerful and unknown sources of energy fueling the Sun's energy output. The same is true of the basis of Kelvin's estimate of the age of the Earth. 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. However, on the whole, he thought that these sources were not adequate to account for anything more than a small faction of the heat lost by the Earth.
Based on these assumptions he at first suggested an age of the Earth of between Ma and Ma. This estimate was actually reduced over his lifetime to between 20 Ma and 40 Ma and eventually to less than 10 Ma. Of course, later scientists, like John Perry and T.
Huxley challenged Kelvin's assumptions. 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.
After this came to light, Kelvin admitted that he might just as well have set his original upper limit on the age of the Earth at 4, Ma instead of Ma. Of course, this was a close as Kelvin ever came to publicly recanting his position.
Later, after radioactivity had been proven to be a significant source of the Earth's internal heat, he did privately that he might have been in error.
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 pointed out that Kelvin's calculations were only as good as the assumptions on which they were based. There is perhaps no beguilement more insidious and dangerous than an elaborate and elegant mathematical process built upon unfortified premises.
Following the discovery of radioactivity by Becquerelthe possibility of using this phenomenon as a means for determining the age of uranium-bearing minerals was demonstrated by Rutherford In his study Rutherford measured the U and He He is an intermediate decay product of U contents of uranium-bearing minerals Potassium-argon dating accuracy international magazines calculate an age. One year later Boltwood developed the chemical U-Pb method.
Boltwood's ages have since been revised. During this same period of time ThomsonCampbell and Wood demonstrated that potassium was radioactive and emitted beta-particles.
The first isotopes of potassium 39 K and 41 K were reported by Aston Kohlhorster reported that potassium also emitted gamma radiation. Newman and Walke also suggested the possibility that 40 K could decay to 40 Ar. However, it was Von Weizsacker's argument, based on the abundance of argon in the Earth's atmosphere relative to the other noble gases He, Ne, Kr, and Xethat 40 K also decayed to 40 Ar by electron capture.
As a test, Von Weizsacker suggested looking for excess 40 Ar in older K-bearing rocks. Thompson and Rowlandsusing a cloud chamber, confirmed that 40 Ar was the decay product of 40 K undergoing electron capture. rapid development of the K-Ar dating method soon followed.
In these studies the isotopic ratios of all the noble gases He, Ne, Ar, Kr, and Xe of neutron-irradiated meteorites were measured. This led to the discovery of 39 Ar, which is derived from 39 K by Merrihue Dating rocks by radioactive timekeepers is simple in theory, but almost all of Potassium-argon dating accuracy international magazines different methods except for the isochron methods - see below rely on these few basic assumptions: All Assumptions Valid for Billions of Years.