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.The passage of time can be charted by the reduction in the number of parent atoms, and the increase in the number of daughter atoms.Radiometric dating can be compared to an hourglass.
Once all of the sand has fallen out of the top, the hourglass will no longer keep time unless it is turned over again.
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.
However, some Christians suggest that the geologic dating techniques are unreliable, that they are wrongly interpreted, or that they are confusing at best.
Unfortunately, much of the literature available to Christians has been either inaccurate or difficult to understand, so that confusion over dating techniques continues.