Non-Constant Decay Rates

[darkmatter4brains]

anybody know more about this? How valid is it?

http://www.msnbc.msn.com/id/38863989/from/toolbar

http://news.stanford.edu/news/2010/augu ... 82310.html

It's a mystery that presented itself unexpectedly: The radioactive decay of some elements sitting quietly in laboratories on Earth seemed to be influenced by activities inside the sun, 93 million miles away.

Is this possible?

Researchers from Stanford and Purdue University believe it is. But their explanation of how it happens opens the door to yet another mystery.

There is even an outside chance that this unexpected effect is brought about by a previously unknown particle emitted by the sun. "That would be truly remarkable," said Peter Sturrock, Stanford professor emeritus of applied physics and an expert on the inner workings of the sun.

The story begins, in a sense, in classrooms around the world, where students are taught that the rate of decay of a specific radioactive material is a constant. This concept is relied upon, for example, when anthropologists use carbon-14 to date ancient artifacts and when doctors determine the proper dose of radioactivity to treat a cancer patient.

 

[emperor_of_localgroup]

I always get a guts feeling
the sun is not exactly what we see.
Its contribution to the solar system is not only
its gravity, but has other hidden effects
which are still unknown to us.

We may now seek a new explanation of muons's decay and special relativity.

 

[captdude]

I believe the total effect of gravity is unknown to us...........

 

[darkmatter4brains]

The potential for the mysterious paricle coming from the Sun was definitely cool.

But, I thought the real clincher in this article, was the fact that the fundmental assumption that we use in dating artifacts, etc. may be wrong - that decay rates are not actually constant, leaving the carbon 14 dating method and others questionable. The question is, if this is true, how far off are our historical timelines? I would imagine the effect would only be significant for very early dates, but I don't know. I would also imagine there are ways to calibrate the dating methods based on decay rates, by either methods that don't involve decay rates, or by actual historical documents. Presumably, you would also think calibration methods would have already discovered the problem mentioned in the article?

I'm surprised nobody commented on that fact, but it would be cool to see somebody who is familar with daing techniques to weigh in on this

 

[darkmatter4brains]

From wikipedia on calibrating carbon 14 dating

After reading this, I have no idea what effect non-constant decay rates would have on all this :lol:

I would imagine once you characterize the variations in the decay rates, if they do indeed exist, it would just require a modification to the calibration, but I'm not sure on that.

I would also imagine the larger those variations, potentially the further off on our dates we could be, but it sounds like they calibrate against other non-radioactive sources, so it really does seem like we would have run into a problem already from non-constant decay rates?

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Calibration
[edit] The need for calibration

Calibration curve for the radiocarbon dating scale. Data sources: Stuiver et al. (1998).[10] Samples with a real date more recent than AD 1950 are dated and/or tracked using the N- & S-Hemisphere graphs. See preceding figure.A raw BP date cannot be used directly as a calendar date, because the level of atmospheric 14C has not been strictly constant during the span of time that can be radiocarbon dated. The level is affected by variations in the cosmic ray intensity which is in turn affected by variations in the Earth's magnetosphere [11]. In addition, there are substantial reservoirs of carbon in organic matter, the ocean, ocean sediments (see methane hydrate), and sedimentary rocks. Changes in the Earth's climate can affect the carbon flows between these reservoirs and the atmosphere, leading to changes in the atmosphere's 14C fraction.

Aside from these changes due to natural processes, the level has also been affected by human activities. From the beginning of the industrial revolution in the 18th century to the 1950s, the fractional level of 14C decreased because of the admixture of large quantities of CO2 into the atmosphere, due to the excavated oil reserves and combustion production of fossil fuel. This decline is known as the Suess effect, and also affects the 13C isotope. However, atmospheric 14C was almost doubled for a short period during the 1950s and 1960s due to atmospheric atomic bomb tests.

As a consequence, the radiocarbon method shows limitations on dating of materials that are younger than the industrial era. Due to these fluctuations, greater carbon-14 content cannot be taken to mean a lesser age. It is expected that in the future the radiocarbon method will become less effective. A calibration curve must sometimes be combined with contextual analysis, because there is not always a direct relationship between age and carbon-14 content.[12]

[edit] Calibration methods
The raw radiocarbon dates, in BP years, are calibrated to give calendar dates. Standard calibration curves are available, based on comparison of radiocarbon dates of samples that can be dated independently by other methods such as examination of tree growth rings (dendrochronology), deep ocean sediment cores, lake sediment varves, coral samples, and speleothems (cave deposits).

The calibration curves can vary significantly from a straight line, so comparison of uncalibrated radiocarbon dates (e.g., plotting them on a graph or subtracting dates to give elapsed time) is likely to give misleading results. There are also significant plateaus in the curves, such as the one from 11,000 to 10,000 radiocarbon years BP, which is believed to be associated with changing ocean circulation during the Younger Dryas period. Over the historical period from 0 to 10,000 years BP, the average width of the uncertainty of calibrated dates was found to be 335 years, although in well-behaved regions of the calibration curve the width decreased to about 113 years while in ill-behaved regions it increased to a maximum of 801 years. Significantly, in the ill-behaved regions of the calibration curve, increasing the precision of the measurements does not have a significant effect on increasing the accuracy of the dates.[13]

The 2004 version of the calibration curve extends back quite accurately to 26,000 years BP. Any errors in the calibration curve do not contribute more than ±16 years to the measurement error during the historic and late prehistoric periods (0 - 6,000 yrs BP) and no more than ±163 years over the entire 26,000 years of the curve, although its shape can reduce the accuracy as mentioned above.[14]

In late 2009, the journal Radiocarbon announced agreement on the INTCAL09 standard, which extends a more accurate calibration curve to 50,000 years.[15][16]

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