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The mathematical formula that is used to figure the age of the rock depends on the [[half-life]] of potassium-40 (the time it takes for half the potassium-40 in a given sample to decay). The half-live of potassium-40 is approximately 1.26 billion years (that is, 1.26x10<sup>9</sup> years).
The mathematical formula that is used to figure the age of the rock depends on the [[half-life]] of potassium-40 (the time it takes for half the potassium-40 in a given sample to decay). The half-live of potassium-40 is approximately 1.26 billion years (that is, 1.26x10<sup>9</sup> years).
Obviously, this formula depends on the laws of physics remaining constant over time. If the rate of [[radioactive decay]] has changed over time, the formula will not give correct dates. Most scientists believe that the rate of potassium-argon decay has not changed over the history of the earth. However, some creationists have argued that God increased the rate of potassium-argon decay during the first few days of Creation, thus causing the potassium-argon dating method to give erroneously old date readings.<ref>http://creationwiki.org/Carbon-14_dating#RATE_Group.27s_Research</ref>
Obviously, this formula depends on the laws of physics remaining constant over time. If the rate of [[radioactive decay]] has changed over time, the formula will not give correct dates. Most scientists believe that the rate of potassium-argon decay has not changed over the history of the earth. However, some creationists have argued that God increased the rate of potassium-argon decay during the first few days of Creation, thus causing the potassium-argon dating method to give erroneously old date readings.
Other isotopes with shorter half-lives can also be used to date objects- however, each method has its own drawbacks. For instance, the decay of carbon-14 is often used to complement the potassium-argon dating of [[dinosaur]] [[fossils]].
Other isotopes with shorter half-lives can also be used to date objects- however, each method has its own drawbacks. For instance, the decay of carbon-14 is often used to complement the potassium-argon dating of [[dinosaur]] [[fossils]].
Isotopes: Principles and Applications, by G. Faure and T. Mensing (Wiley & Sons, 2005).
Isotopes: Principles and Applications, by G. Faure and T. Mensing (Wiley & Sons, 2005).
[[category:geology]]
[[Category:Earth science]]