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.He was employed at Caltech's Division of Geological & Planetary Sciences at the time of writing the first edition.
Radiometric dating techniques indicate that the Earth is thousands of times older than that--approximately four and a half billion years old.
Many Christians accept this and interpret the Genesis account in less scientifically literal ways.
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.
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.