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Basic understanding of how radiometric dating works is useful. This lesson is highly simplified, and the powerpoint describes everything the student will need to know for the activity.The radioactive half-life for a given radioisotope is a measure of the tendency of the nucleus to "decay" or "disintegrate" and as such is based purely upon that probability.The tiny nuclear size compared to the atom and the enormity of the forces which act within it make it almost totally impervious to the outside world.Fossils are generally found in sedimentary rock not igneous rock.Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years.The half life of a radioactive element is the average time it takes for one half of the mass to radioactively decay into another element or isotope.
Relative age will require the comparison of two or more objects, whereas absolute age does not.For example, if an area used for trash has modern refuse in it such as CDs and computers, and the layer underneath has cans made of tin, then it is safe to say the layer of tin cans have a greater relative age than the layer with modern refuse.However, this does not say anything about the absolute age of the layers.So in order to date most older fossils, scientists look for layers of igneous rock or volcanic ash above and below the fossil.Scientists date igneous rock using elements that are slow to decay, such as uranium and potassium.
The only thing which can alter the half-life is direct nuclear interaction with a particle from outside, e.g., a high energy collision in an accelerator.