Changes

== Basic mechanism ==

== Basic mechanism ==

Radiometric dating proceeds from the fact that certain substances (radioactive isotopes) decay, with near-clockwork accuracy, into other elements, and that the old elements and the new elements can be chemically distinguished and can be quantitatively measured.  Even the individual isotopes of an element can be accurately measured, though they can't be chemically separated.  The radioactive decay of a given isotope proceeds by a well-known [[Radioactivity#Exponential_decay_and_half-life|exponential decay function]] involving a "half-life" for that isotope:

Radiometric dating proceeds from the fact that certain substances (radioactive isotopes) decay, with near-clockwork accuracy, into other elements, and that the old elements and the new elements can be chemically distinguished and can be quantitatively measured.  Even the individual isotopes of an element can be accurately measured, though they can't be chemically separated.  The radioactive decay of a given isotope proceeds by a well-known [[Radioactivity#Exponential decay and half-life|exponential decay function]] involving a "half-life" for that isotope:

::<math>e^{-\frac{log(2)}{H}\ t}</math>

::<math>e^{-\frac{log(2)}{H}\ t}</math>

where H is the half-life.

where H is the half-life.

Needless to say, radiometric dating is not easy.  It requires very careful measurement and analysis technique, as well as careful analysis of the assumptions, about such things as the purity and composition of the samples, to do this effectively.  There are also assumptions about the accuracy of the equipment involved, and, of course, assumptions about the fundamental physics involved.  The findings of the scientific community, on such things as the age of the Earth and the dates of various epochs (e.g. Permian, Triassic, Cretaceous, Paleogene) are the result of decades of measurement and analysis by hundreds of people.

Needless to say, radiometric dating is not easy.  It requires very careful measurement and analysis technique, as well as careful analysis of the assumptions, about such things as the purity and composition of the samples, to do this effectively.  There are also assumptions about the accuracy of the equipment involved, and, of course, assumptions about the fundamental physics involved.  The findings of the scientific community, on such things as the age of the Earth and the dates of various epochs (e.g. Permian, Triassic, Cretaceous, Paleogene) are the result of decades of measurement and analysis by hundreds of people.

All scientific investigations involve three general types of asumptions:

All scientific investigations involve three general types of assumptions:

#The scientists doing the investigation know how to perform the investigation&mdash;in short, they know what they are doing.  If one is investigating temperature patterns to draw conclusions and predictions about weather, this means that the investigators understand the subject matter, and understand the connection between temperature and weather patterns.

#The scientists doing the investigation know how to perform the investigation&mdash;in short, they know what they are doing.  If one is investigating temperature patterns to draw conclusions and predictions about weather, this means that the investigators understand the subject matter, and understand the connection between temperature and weather patterns.

#The equipment works, is properly maintained, and is properly calibrated.  That is, the thermometers work properly.

#The equipment works, is properly maintained, and is properly calibrated.  That is, the thermometers work properly.