Talk:Carbon-14 dating

The last paragraph is out of date, and the suggestion that a lack of rainbows means a different ratio of C-12 to C-14 is weird. Suggest changing to

-- One potential problem with C-14 dating is that there is no guarantee that the ratio of C-14 in the atmosphere has been constant; if there was less C-14 in the atmosphere in the past than there is today, samples will date older than their correct age; if more C-14, they will date too recent. The amount of C-14 in the atmosphere could have changed for several reasons, incluing reductions in the ozone layer which allow more cosmic rays to enter the lower atmosphere, burning of fossil fuels which are depleted of C-14 and the detonation of nuclear devices. Some creationists have claimed that since the Bible says there was no rainbow before the flood, the atmosphere must have been significantly altered during the flood, though how this might affect the ratio of C-14 is unclear.

Recently, scientists have questioned this assumption, and have investigated methods of calibrating and validating C-14 ages. One method involves comparing the C-14 age of tree-rings, ice cores or lake floor sediments with the age obtained by counting annual layers; an example from Lake Suigetsu in Japan, which includes graphs showing the close correspondence between ages determined by C-14 dating and ages determined by counting annual layers, can be found at http://home.entouch.net/dmd/suigetsu.htm

The current results show that C-14 dating produces ages that are fractionally younger than the true age of the material. --

As the quote from Seagraves suggests, C-14 dating effectively measures the time the carbon in an object/organism was part of a land plant. Land animals can be effectively carbon-dated since they obtain their carbon directly or indirectly from land plants; however marine creatures (including seals, penguins and molluscs) obtain their carbon from marine sources, including CO2 and calcium carbonate dissolved in seawater. Since some of this carbon comes from sediments, and even the carbon which originated from land plants may have been in the marine environment for some time, C-14 dating of marine organisms should not be expected to give the age of the organism.

--

One currently favoured hypothesis for the existence of C-14 in ancient coal which should be mentioned is that C-14 is generated within the coal in the same way that it is generated within the atmosphere, but at a much reduced rate due to the inaccessibility of the material. Roy 13:24, 6 Jun 2005 (GMT)

Query: partial pressure
In the Conclusion section: Today we have evidence of global warming, and holes in the ozone layer; indicating a change in both composition and partial pressure of the atmosphere that could cause higher rates of C-14 production.

I looked up Partial pressure in Wikipedia and found that it is the pressure that would be exerted by a particular gas in a mixture if it alone occupied all the volume of the gases being measured. Therefore it seems to be a fundamental characteristic of that gas. It would change only if the characteristics of that gas changed or else it would change in step with the total pressure of the mixture.

I cannot see anything in the circumstances of the flood to change the characteristics of a gas, which means that this should refer only to the second possibility; but that is no more than to say that the atmospheric pressure has changed. First, is there any evidence for that? Second, why would that change 14C production? and third, it would be simpler to say just that.

Since partial pressure is a characteristic of a single gas in a mixture, it also seems wrong to talk about the partial pressure of the atmosphere.

Oelphick 01:11, 1 October 2006 (EDT)

Partial pressure of a gas is the portion of the total pressure of the mixture of gases attributable to that one gas. The partial pressure of water vapor in the atmosphere is related to the absolute humidity of the atmosphere. If you were to remove that one gas, the pressure of the mixture that was left would drop by that amount. The partial pressure depends on characteristics of the gas (for example the mass of each molecule), and the number of molecules of the gas, but is not a characteristic of the gas. Partial pressure is just another way to refer to the amount of a given gas in the atmosphere.

The flood could certainly change the percentage which any given gas molecule adds to the total. More carbon dioxide could be vented from volcanoes, or fall from space or something, adding to the partial pressure of carbon dioxide. If there is more carbon dioxide there is a better chance that there is more carbon-14 The conclusion is not wrong, but maybe should be changed to avoid confusion.

--John Baab 14:45, 3 August 2007 (EDT)