Changes

Because radiometric dating fails to satisfy standards of testability and [[falsifiability]], claims based on radiometric dating may fail to qualify under the ''[[Daubert]]'' standard for court-admissible scientific evidence.  It is more accurate for shorter time periods (e.g., hundreds of years) during which control variables are less likely to change.

Because radiometric dating fails to satisfy standards of testability and [[falsifiability]], claims based on radiometric dating may fail to qualify under the ''[[Daubert]]'' standard for court-admissible scientific evidence.  It is more accurate for shorter time periods (e.g., hundreds of years) during which control variables are less likely to change.

Radiometric dating (often called radioactive dating) is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and can be used to date a wide range of natural and man-made materials. Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geological time scale. Among the best-known techniques are radiocarbon dating, potassium-argon dating and uranium-lead dating. By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change. Radiometric dating is also used to date archaeological materials, including ancient artifacts.

 

Different methods of radiometric dating vary in the timescale over which they are accurate and the materials to which they can be applied.

There are a number of implausible assumptions involved in radiometric dating with respect to long time periods.

 

 

One key assumption is that the initial quantity of the parent element can be determined.  With uranium-lead dating, for example, you must be able to determine how much uranium was in the sample to start with.  One assumption that can be made is that all the lead in the sample was once uranium, but if there was lead there to start with, this assumption is not valid, and any date based on that assumption will be incorrect (too old).

 

In the case of carbon dating, it is not the initial quantity that is important, but the initial ratio of C¹⁴ to C¹², but the same principle otherwise applies.

 

=== Rate of decay ===

 

Another assumption is that the rate of decay is constant.

There is no reason to expect that the rate of decay of a radioactive material is largely constant,<ref>At least one example of a change in the rate has been observed in laboratory experiments.  See Walker, 2000.</ref> and it was almost certainly not constant near the creation or beginning of the universe.

The process of decay is as follows.  Atoms consist of a heavy central core called the [[nucleus]] surrounded by clouds of lightweight particles (electrons), called [[electron shell]]s. The energy locked in the nucleus is enormous, but cannot be released easily. The phenomenon we know as heat is simply the jiggling around of atoms and their components, so in principle a high enough temperature could cause the components of the core to break out. However, the temperature required to do this is in in the millions of degrees, so this cannot be achieved by any natural process that we know about. The second way that a nucleus could be disrupted is by particles striking it. However, the nucleus has a strong positive charge and the electron shells have a strong negative charge. Any incoming negative charge would be deflected by the electron shell and any positive charge that penetrated the electron shells would be deflected by the positive charge of the nucleus itself.

 

 

It is important that the sample not have had any outside influences.  One example of this can be found in metamorphic rocks.<ref>[http://www.tulane.edu/~sanelson/eens211/radiometric_dating.htm Radiometric Dating] Course notes for  EENS 211 at Tulane University</ref>  This does not mean that all rock samples are unreliable, but it is possible to account for a process which throws off the data for metamorphic rocks.

 

For example, with [[Uranium-lead dating]] with the crystallization of magma, this remains a closed system until the uranium decays.  As it decays, it disrupts the crystal and allows the lead atom to move.  Likewise, heating the rock such as [[granite]] forms [[gneiss]] or [[basalt]] forms [[schist]].  This can also disrupt the ratios of lead and uranium in the sample.

== Calibration ==

== Calibration ==