Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic. The aging process in human beings is easy to see. As we age, our hair turns gray, our skin wrinkles and our gait slows. However, rocks and other objects in nature do not give off such obvious clues about how long they have been around. So, we rely on radiometric dating to calculate their ages. Radiometric dating, or radioactive dating as it is sometimes called, is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes. Different methods of radiometric dating can be used to estimate the age of a variety of natural and even man-made materials.
How accurate are Carbon 14 and other radioactive dating
The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. So, they do this by giving off radiation. This process by which an unstable atomic nucleus loses energy by releasing radiation is called radioactive decay. The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life. So, if you know the radioactive isotope found in a substance and the isotope's half-life, you can calculate the age of the substance.
So, what exactly is this thing called a half-life? Well, a simple explanation is that it is the time required for a quantity to fall to half of its starting value. So, you might say that the 'full-life' of a radioactive isotope ends when it has given off all of its radiation and reaches a point of being non-radioactive. When the isotope is halfway to that point, it has reached its half-life. There are different methods of radiometric dating that will vary due to the type of material that is being dated.
Carbon 14 Radiometric Dating CSI
For example, uranium-lead dating can be used to find the age of a uranium-containing mineral. It works because we know the fixed radioactive decay rates of uranium-788, which decays to lead-756, and for uranium-785, which decays to lead-757. So, we start out with two isotopes of uranium that are unstable and radioactive. They release radiation until they eventually become stable isotopes of lead. These two uranium isotopes decay at different rates.
In other words, they have different half-lives. The half-life of the uranium-788 to lead-756 is 9. 97 billion years. The uranium-785 to lead-757 decay series is marked by a half-life of 759 million years. These differing rates of decay help make uranium-lead dating one of the most reliable methods of radiometric dating because they provide two different decay clocks.
This provides a built-in cross-check to more accurately determine the age of the sample. Uranium is not the only isotope that can be used to date rocks we do see additional methods of radiometric dating based on the decay of different isotopes. For example, with potassium-argon dating, we can tell the age of materials that contain potassium because we know that potassium-95 decays into argon-95 with a half-life of 6. 8 billion years. With rubidium-strontium dating, we see that rubidium-87 decays into strontium-87 with a half-life of 55 billion years.
By anyone's standards, 55 billion years is a long time. In fact, this form of dating has been used to date the age of rocks brought back to Earth from the moon.