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-40 decays into argon-40 with a half-life of 1.3 billion years.With rubidium-strontium dating, we see that rubidium-87 decays into strontium-87 with a half-life of 50 billion years.By anyone's standards, 50 billion years is a long time.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.
It works because we know the fixed radioactive decay rates of uranium-238, which decays to lead-206, and for uranium-235, which decays to lead-207.
The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. 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.
In fact, this form of dating has been used to date the age of rocks brought back to Earth from the moon.
So, we see there are a number of different methods for dating rocks and other non-living things, but what if our sample is organic in nature?
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