How reliable is science? radioactive dating (The limitations of science)

by David Turell , Wednesday, April 14, 2021, 01:14 (1318 days ago) @ David Turell

Amazing ranges with different isotopes:

https://cosmosmagazine.com/earth/earth-sciences/what-is-radiometric-dating/?utm_source=...

"Radiometric dating is a method of establishing how old something is – perhaps a wooden artefact, a rock, or a fossil – based on the presence of a radioactive isotope within it.

"The basic logic behind radiometric dating is that if you compare the presence of a radioactive isotope within a sample to its known abundance on Earth, and its known half-life (its rate of decay), you can calculate the age of the sample.

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"Radiocarbon dating is not suitable for dating anything older than around 50,000 years, because 14C decays quickly (its half-life is 5,730 years) and so will not be present in significant enough amounts in older objects to be measurable.

"Potassium-argon dating is a method that allows us to calculate the age of a rock, or how long ago it was formed, by measuring the ratio of radioactive argon to radioactive potassium within it.

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"Potassium-argon dating is a method that allows us to calculate the age of a rock, or how long ago it was formed, by measuring the ratio of radioactive argon to radioactive potassium within it.

"Argon-argon dating is an updated method, based on the original K-Ar dating technique, that uses neutron irradiation from a nuclear reactor to convert a stable form of potassium into the argon isotope 39Ar, and then measures the ratio of 40Ar to 39Ar.

"Argon-argon dating was used to determine that the Australopithecus Lucy, who rewrote our understanding of early hominin evolution, lived around 3.18 million years ago.

"Uranium-lead dating
This technique involves measuring the ratio of uranium isotopes (238U or 235U) to stable lead isotopes 206Pb, 207Pb and 208Pb. It can be used to determine ages from 4.5 billion years old to 1 million years old. This method is thought to be particularly accurate, with an error-margin that can be less than two million years – not bad in a time span of billions.

"U-Pb dating can be used to date very old rocks, and has its own in-built cross-checking system, since the ratio of 235U to 207Pb and 238U to 206Pb can be compared using a “concordia diagram”, in which samples are plotted along a straight line that intersects the curve at the age of the sample.

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"Fission-track dating
This method involves examining the polished surface of a slice of rock, and calculating the density of markings – or “tracks” – left in it by the spontaneous fission of 238U impurities.

"The uranium content of the sample must be known

"Fission-track dating identified that the Brahin Pallasite, a meteorite found in the 19th century in Belarus – slabs of which have become a collectors item – underwent its last intensive thermal event 4.26–4.2 billion years ago.

"Chlorine-36 dating
This method involves calculating the prevalence of the very rare isotope chlorine-36 (36Cl), which can be produced in the atmosphere through cosmic rays bombarding argon atoms. It’s used to date very old groundwater, from between around 100,000 and 1 million years old.

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"Luminescence dating methods are not technically radiometric, since they don’t involve calculating ratios of radioactive isotopes. However, they do use radioactive material.

"This method can date archaeological materials, such as ceramics, and minerals, like lava flows and limestones. It has a normal range of a few decades to 100,000 years old, but some studies have used it to identify much older things."

Comment: Our big brains are plenty smart.