The sand grains at the top of the sealed glass are like the atoms of the parent isotope in the rock, and those at the bottom like the atoms of the daughter.
Radioactive decay is where the parent atoms change as a result of radioactive decay into daughter atoms, like the individual grains of sand falling from the top to the bottom of the glass.
But it’s not difficult to understand the basic principles to realize that alleged ages of millions of years have not been measured objectively, but derived from subjective assumptions.
Radioactive dating begins by carefully measuring the concentrations of radioactive isotopes in rocks.
Everything is composed of elements and there are about 90 naturally occurring ones, such as hydrogen, carbon, oxygen and iron.
Each element comes in different forms, called isotopes, most of which are stable and do not change.
Unlike the hourglass, we do not know how much of each isotope was in the rock in the beginning.
That’s because we did not observe what happened in the past when the rock formed.Each dating method uses different kinds of assumptions to get around this problem for radiometric dating—the deadly problem caused by the fact that we cannot make measurements in the past.Apart from the fatal problem of not knowing the initial conditions, there is another problem that is just as deadly.The hourglass depends on the sand falling at a regular rate.Like an hour glass, it is said, you simply measure the parent and the daughter elements and you can calculate the age.For example, there is a radioactive form of potassium (potassium-40) that decays into argon (argon-40).