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Message:: [QUOTE="Suarez, post: 3378471, member: 99239"]This is in response to the below question posted on the Proculus thread: "Is there a scientific test to know the exact age of a coin ?" I think you're thinking of something along the lines of carbon dating. Not with today's technology but perhaps not terribly far-fetched at some point in the future. You can use carbon as a dating tool for figuring out the approximate date of manufacture because a particular isotope of this element, carbon-14 if memory serves, is radioactive. Since radioactive elements decay at a steady rate you can compare the amount of C14 (or whatever that particular isotope is) to the amount available in nature and use the difference to calculate the period necessary to reach the depletion rate observed. Problem is, carbon is by definition a molecule of organic origin where metals are inorganic. There being no carbon inside a coin, logic goes, you can't use this method. The atoms that make up a coin were formed in supernovae billions of years ago and remain stable to this day. It doesn't matter - again, just using basic common sense - whether those atoms were in an ore vain or inside a coin. But, as a thought experiment at least, I'd like to challenge the standard thinking. There are at least three possibilities that come to mind. First, coming back to carbon dating, the deciding factor on whether an object can be dated this way largely falls on whether there's a big enough piece of it to test. If it's wood a splinter won't do, you need x grams' worth. If it's a piece of cloth a single thread is insufficient, you need a patch of a certain size and so on. This is because the instrument that is going to analyze the sample needs a minimum threshold amount below which the amount of radioactive carbon is undetectable. That highlights that this is simply a matter of a practical, and not a theoretical, limitation. There is nothing that suggests to me that it is absolutely impossible that the amount of carbon accidentally trapped in the alloying process (say from workshop smoke) will be forever below the limits of detection. There may come a time in the not distant future when just a nanogram or two of carbon is sufficient to make such an analysis. Second, and in a similar vein to carbon, there are many other elements with radioactive isotopes. A volcanic eruption may create an unstable form of potassium which lingers in the atmosphere. A few of these atoms could, and likely are, continuously trapped in everyday objects as they're made (potentially including coins). In so doing this creates the opportunity for a very sensitive instrument to potentially be able to measure the amount of radioactivity vis a vis background radiation and give us a probable date range of manufacture. So we're not limited to just carbon. Lastly, I think perhaps one of the most promising avenues could be acoustic analysis. When a metal is cooled from a molten state its internal composition assumes a latticed structure according to its crystalline habit. When this structure is compressed (as would occur when it's hammered) at a microscopic level you find that the shock waves create layering and fractures; alternating areas of higher and lower spacing. In effect, some of the energy transferred in the blows has not dissipated immediately in the form of heat but is stored like an accordion or a spring. These atoms and molecules slowly lose that energy and relax to their initial state. This 'relaxation' happens at a steady rate that can take place immediately or span thousands (millions?) of years depending on the material. It is this steady rate that could potentially be exploited as a means of dating. By knowing the alloy's makeup and its atomic organization in its most relaxed state (molten), measuring the current level of stress and, finally, the rate of this particular alloy's relaxation (or elasticity) you can then make a computation that would give you such a mint date. The first two of these values can be determined today. There are several commercially available methods for determining exact metallic composition of an object, this is the easy part. Stress can be analyzed with ultrasound and there are several available methods that can give you acoustic analyses today. The last variable would be the rate of elasticity for any given metal or combination of metals. This would take some engineering or computational modelling to figure out but is a fairly straightforward project. That there is as yet no purpose built analyzer that incorporates all three of these to spit out a number has everything to do with there not being a commercial market to justify the R&D but the tech is there now, it's not science fiction.[/QUOTE]

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