Some of the atoms eventually change from one element to another by a process called radioactive decay.
If there are a lot of atoms of the original element, called the parent element, the atoms decay to another element, called the daughter element, at a predictable rate.
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.
Similarly, when all the atoms of the radioactive element are gone, the rock will no longer keep time (unless it receives a new batch of radioactive atoms).
In the process the paper refutes a number of misconceptions prevalent among Christians today.This paper is available on the web via the American Scientific Affiliation and related sites to promote greater understanding and wisdom on this issue, particularly within the Christian community.Introduction Overview The Radiometric Clocks Examples of Dating Methods for Igneous Rocks Potassium-Argon Argon-Argon Rubidium-Strontium Samarium-Neodymium, Lutetium-Hafnium, and Rhenium-Osmium Uranium-Lead The Age of the Earth Extinct Radionuclides: The Hourglasses that Ran Out Cosmogenic Radionuclides: Carbon-14, Beryllium-10, Chlorine-36 Radiometric Dating of Geologically Young Samples Non-Radiogenic Dating Methods for the Past 100,000 Years Ice Cores Varves Other Annual-Layering Methods Thermoluminescence Electron Spin Resonance Cosmic Ray Exposure Dating Can We Really Believe the Dating Systems? Rightly Handling the Word of Truth Arguments over the age of the Earth have sometimes been divisive for people who regard the Bible as God's word.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.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.