Potassium argon radioactive dating works because
You have a sneaky, but not especially clever, roommate who doesn't like the ice cream itself, but cannot resist picking out eating the chips – and in an effort to avoid detection, he replaces each one he consumes with a raisin.
He is afraid to do this with all of the chocolate chips, so instead, each day, he swipes half of the number of remaining chocolate chips and puts raisins in their place, never quite completing his diabolical transformation of your dessert, but getting closer and closer.
Scientists interested in figuring out the age of a fossil or rock analyze a sample to determine the ratio of a given radioactive element's daughter isotope (or isotopes) to its parent isotope in that sample.U-Pb dating is often used to date igneous (volcanic) rocks, which can be hard to do because of the lack of fossils; metamorphic rocks; and very old rocks.All of these are hard to date with the other methods described here.To understand radiometric dating techniques, you first have to have an understanding of what is being measured, how the measurement is being made and the theoretical as well as practical limitations of the system of measurement being used.As an analogy, say you find yourself wondering, "How warm (or cold) is it outside?
Rubidium-strontium (Rb-Sr) dating: Radioactive rubidium-87 decays into strontium-87 with a half -life of 48.8 billion years.