Assumptions made in radiometric dating

After all, textbooks, media, and museums glibly present ages of millions of years as fact.

Yet few people know how radiometric dating works or bother to ask what assumptions drive the conclusions.

These parent radioisotopes change into daughter lead-206, lead-207, argon-40, strontium-87, and neodymium-143 isotopes, respectively.

Thus geologists refer to uranium-lead (two versions), potassium-argon, rubidium-strontium, or samarium-neodymium dates for rocks.

Examples are granites (formed by cooling under the ground) and basalts (formed by cooling of lava at the earth’s surface).

The next step is to measure the amount of the parent and daughter isotopes in a sample of the rock unit.

It is the interpretation of these chemical analyses that raises potential problems.

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So, in general, few people quarrel with the resulting chemical analyses.Both are complete atoms in every sense of the word.Geologists regularly use five parent isotopes to date rocks: uranium-238, uranium-235, potassium-40, rubidium-87, and samarium-147.Actually, it isn’t really a decay process in the normal sense of the word, like the decay of fruit.The daughter atoms are not lesser in quality than the parent atoms from which they were produced.So, for example, every carbon atom contains six protons and six electrons, but the number of neutrons in each nucleus can be six, seven, or even eight.

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