Radiometric dating parent daughter isotopes
Say a second friend who is aware of this arrangement visits and notices that your carton of ice cream contains 70 raisins and 10 chocolate chips.
She declares, "I guess you went shopping about three days ago." How does she know this?
Uranium-lead (U-Pb) dating: Radioactive uranium comes in two forms, uranium-238 and uranium-235.
The number refers to the number of protons plus neutrons.
If you want to know how old someone or something is, you can generally rely on some combination of simply asking questions or Googling to arrive at an accurate answer.
This applies to everything from the age of a classmate to the number of years the United States has existed as a sovereign nation (243 and counting as of 2019).
This is because when radioactive elements first come into being, they are presumed to consist entirely of a single isotope.
Imagine that you enjoy a certain kind of ice cream flavored with chocolate chips.
This in turn depends in the approximate expected age of the object because radioactive elements decay at enormously different rates.
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?
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.Many substances, however, both biological and chemical, conform to a different mechanism: In a given time period, half of the substance will disappear in a fixed time no matter how much is present to start with.