Pictures of radioactive dating
However, usually it is not possible to apply this formula directly, because, for instance, in many cases we do not know the original amount of the radioactive isotope when the rock was solidified.Also, such a calculation does not provide us with any statistical error margin to double-check the result.Pro The half life of radioactive substances are empirically determined.The ratio of the parent to daughter atoms can be used to determine an exact age given the assumptions that none of the original parent atoms have been eroded or lost during the time being calculated.Details about linear regression are available in any elementary statistics book, or online -- see [Linear2013].Here are just four examples of isochron graphs, which are entirely typical among the tens of thousands of examples that could be mentioned.
But if we have multiple data points -- multiple measurements of different samples say within a single igneous rock, then these should all lie on a straight line, whose slope m is simply related to the age of the specimen by the formula m = e; instead, this original ratio actually comes out as a result of the calculation!
Quantum mechanics is one of two cornerstones of modern physics (the other is general relativity), and has been precisely confirmed in thousands of very exacting experiments.
For these reasons, scientists have considerable confidence in these dates when they are measured properly in accordance with procedures that have been developed and refined over several decades.
Of course, in real scientific research, scientists do not rely on manually drawing points on graph paper to determine a best-fit straight line or to determine the line's slope or y-intercept.
Instead, they use a statistical technique known as linear regression, which computes the least-squares best fit of a straight line through a sequence of points.Fortunately, scientists have developed several methods that not only circumvent the difficulty of not knowing the original amounts, but also provide a very reliable means of statistical validity checking.