Radioactive dating using potassium argon
Radioactive dating methods—many of which are quite elaborate—have numerous physical condition requirements that cannot realistically remain unaffected over millions and perhaps billions of years.
Since the potassium-argon dating methods clearly appear to be unreliable, why should any rational person trust them to provide accurate dates for rocks?
Radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth.
What simplifies things is that potassium is a reactive metal and argon is an inert gas: Potassium is always tightly locked up in minerals whereas argon is not part of any minerals. So assuming that no air gets into a mineral grain when it first forms, it has zero argon content.The others include helium (He), neon (Ne), krypton (Kr), xenon (Xe), and radon (Rn).