Wiens has a Ph D in Physics, with a minor in Geology.
His Ph D thesis was on isotope ratios in meteorites, including surface exposure dating.
Radiometric dating techniques indicate that the Earth is thousands of times older than that--approximately four and a half billion years old.
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.
Uranium dating (uranium-lead) is good for the entire history of the Earth since U-238 (the parent) has a half-life of 4.4 billion years.
Since the universe is a bit less than 14 billion years old, U-Pb can be used to date anything in the universe.
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.
Many people have been led to be skeptical of dating without knowing much about it. In spite of this, differences still occur within the church.
For example, most people don't realize that carbon dating is only rarely used on rocks. A disagreement over the age of the Earth is relatively minor in the whole scope of Christianity; it is more important to agree on the Rock of Ages than on the age of rocks.
Potassium-argon is the basis for most of the geologic time scale; rubidium-strontium was one of the first isotopic systems to be studied - and these isotopes are also good for studying the mixing of water where, say, rivers merge; and neodymium-samarium can be used for geologic dating but is also good for looking at the origins of various igneous rocks.
There are a lot of isotopic dating methods - but some of them are useful for much more than simply figuring out how old something is.
But because God has also called us to wisdom, this issue is worthy of study.