Radiometric dating is a scientific method for estimating the age of matter, such as rocks and the Earth. The idea of a young Earth, as some interpret the Bible, is not easily compatible with the findings of radiometric dating.
Young earth creationists view the Earth as approximately 6,000 - 10,000 years old, based on a literal interpretation of the Biblical text. Radiometric dating, on the other hand, relies on the measured decay rates of radioactive isotopes of uranium, potassium and other elements. This method provides age estimates for the formation of Earth of around 4.5 billion years.
Scientific instruments cannot directly measure age as a physical property. Age is the length of time an object has existed. If the object, such as a rock or the Earth, was not observed when it was formed, then its age may be estimated by radiometric dating. Radiometric dating methods rely on assumptions about the initial conditions and decay rates of radioactive isotopes, introducing uncertainties in the calculated ages.
The ancient Hebrews were not overly concerned about when creation occurred, nor the precise age of Earth. They would have understood the Genesis account as a testament to God’s power, wisdom, and love, rather than as a source of scientific information about the age of the Earth. When science and faith appear to be in conflict, leaving us unsure what to believe, we should trust the Bible and wait for further light on the details.
Scientists measure radioactive half-lives: how long it takes for half of a radioactive material (parent isotope) to decay into another element (daughter isotope). Using this knowledge, scientists are able to accurately determine the age of a specimen as long as three key assumptions are true. These assumptions are 1) the rate of decay of parent into daughter has remained constant over time; 2) the specimen being examined hasn’t been contaminated; and 3) we know how much of the parent and the daughter were present at the beginning of the decay process.
Assumptions two and three likely hold but are not certain. Scientists have developed methods to understand how much, if any, daughter product existed at the formation of a specimen. The first assumption is assumed to be true, but recent research shows an excess amount of helium in zircon crystals within granite specimens. This shows that decay rates could have been drastically different in the unobservable past. Scientists are aware of the uncertainties, but also find that radiometric dating is repeatable and consistent, even across radiometric methods.
Scientists have not found a way to determine the exact age of the Earth directly from Earth rocks because Earth’s oldest rocks have been recycled and destroyed by plate tectonics. The oldest Earth minerals analyzed to date are crystals from Australia, at 4.04 billion years. Instead, lunar samples and meteorite material are used to estimate when the Earth formed.
Young earth creationists acknowledge that many rock specimens contain at least hundreds of millions of years’ worth of radioactive decay. To account for this, they have proposed accelerated nuclear decay during either creation week or the Flood. However, such accelerated decay would result in immense amounts of heat being generated in rocks, enough to melt the rocks and the Earth's surface. Determining how this heat was dissipated is an ongoing research topic.