When the glass is turned over, sand runs from the top to the bottom.
Radioactive atoms are like individual grains of sand--radioactive decays are like the falling of grains from the top to the bottom of the glass.
Most processes that we are familiar with are like sand in an hourglass.In exponential decay the amount of material decreases by half during each half-life.You cannot predict exactly when any one particular grain will get to the bottom, but you can predict from one time to the next how long the whole pile of sand takes to fall.Once all of the sand has fallen out of the top, the hourglass will no longer keep time unless it is turned over again.It has become increasingly clear that these radiometric dating techniques agree with each other and as a whole, present a coherent picture in which the Earth was created a very long time ago.
Further evidence comes from the complete agreement between radiometric dates and other dating methods such as counting tree rings or glacier ice core layers.
Radiometric dating--the process of determining the age of rocks from the decay of their radioactive elements--has been in widespread use for over half a century.
There are over forty such techniques, each using a different radioactive element or a different way of measuring them.
This paper describes in relatively simple terms how a number of the dating techniques work, how accurately the half-lives of the radioactive elements and the rock dates themselves are known, and how dates are checked with one another.
In the process the paper refutes a number of misconceptions prevalent among Christians today.
Radiometric dating techniques indicate that the Earth is thousands of times older than that--approximately four and a half billion years old.