Radioactive parent (P) atoms decay to stable daughter (D) atoms e.g.

This implies the earth is at least 20 million years old.

Astronomical cycles can also be used to measure relative age.

In other words, half of the radioactive isotope in a sample would have decayed to Nitrogen-14 (N-14) in just 5,730 years.

C-14 dating of carbon-bearing materials is therefore limited to roughly 50,000 years.

In some cases these astronomical cycles in rock appear to have been laid down over some 25 million years (and radiometric dating puts the absolute age of the rock at some 200 million years).

Dating Anomalies Here we outline a few dating methods or 'clocks' that present a dating anomaly when referenced to the widely accepted OE age of 4.6 billion years. At the outset we note C-14 cannot be used to directly date the earth for the simple reason that the unstable C-14 isotope has a half-life of just 5,730 years.

And OE Christians (theistic evolutionists) see no problem with this dating whilst still accepting biblical creation, see Radiometric Dating - A Christian Perspective.

This is the crucial point: it is claimed by some that an old earth supports evolutionary theory and by implication removes the need for biblical creation.

The time required for half the original number of parent atoms to decay is called the half life.