Some atoms eventually change from one element to another by a process called radioactive decay.
If there are many atoms of the original element, called the parent element, the atoms decay to another element, called the daughter element, at a predictable rate.
For many of the dating techniques, we now have had fifty years over which to measure and remeasure half-lives.
Very precise counting of the decay events or the daughter atoms can be done, so that while the number of, for example, rhenium-187 atoms decaying in 50 years is a very small fraction of the total, the resulting osmium-187 atoms can be very precisely counted.
This is not a problem because the production ratio of these two daughter products is precisely known, and is always constant: 11.2% becomes argon-40 and 88.8% becomes calcium-40.
It is possible to date some rocks by the potassium-calcium method, but this is not often done because it is hard to determine how much calcium was initially present. Whenever rock is melted to become magma or lava, the argon tends to escape.
May 2004 Chuck Roche, Ph D One topic for skeptics involves the age of the earth.
Many creationists have argued for a young earth, one less than 15,000 years, while others allow for just a few million years.
This is usually trapped as very tiny air bubbles in the rock. This would most likely be the case in either young rocks that have not had time to produce much radiogenic argon, or in rocks that are not abundant in potassium.Most do not realize the scientific community is rather unified on the earth being several billion years in age.The most straightforward dating technique is emphasized in this paper – radiometric dating.Rocks are made up of many individual crystals, and each crystal is usually made up of at least several different chemical elements such as iron, magnesium, and silicon.Most elements in nature are stable and do not change into other elements.Any daughter atoms from radioactive decays occurring after a rock cools are trapped where they are made within the rock.These atoms are like the sand grains accumulating in the bottom of the hourglass.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.When all the atoms of the radioactive element are gone, the rock no longer keeps time.By the time ten of these intervals, or half-lives, have passed, less than one thousandth of the original number of radioactive atoms is left.There is no way to change the rate at which radioactive atoms decay.