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*To*: <dinosaur@usc.edu>*Subject*: Re: When is a Year Not a Year?*From*: "philidor11" <philidor11@snet.net>*Date*: Mon, 8 Jul 2002 18:50:23 -0400*References*: <007701c226c7$b1dea0e0$13d33ccc@oemcomputer> <3D2A0D62.8FC896CD@alphalink.com.au>*Reply-to*: philidor11@snet.net*Sender*: owner-dinosaur@usc.edu

HP Dann Pigdon stated: <No radiometric dates are calendar years (and even calendar years aren't "real" years, hence the constant recalibration with leap years, etc). However some are closer than others.> I'm willing to accept that a calendar year is a reasonable approximation of the time required for one full rotation of the Earth around the sun, in the same way that I can accept there is a working solution to equations involving pi. Age has granted me tolerance. There is an inverse relation between philosophical discussion and sleep attained. He adds that: <...Put all those factors together, and you get quite a deviation from "calendar" years (assuming even those are useful). I suspect other radio-isotopes have more predictable original ratios.> and responds to HP Hecht's statement: < Other radioisotope years are "real" years.> with: <Not exactly. They are statistical likelyhoods, assuming a constant rate of radioactive decay.> So, if I'm following correctly, he means that: - dates have a substantial range of error or - dates are not expressed in calendar years or - both. I'm inclined to think that the correct answer is that when mya dates are given for the Maastrichtian, for example, that these are referring to calendar years, but that they could be off. If so, is there a good rule of thumb possible error percentage to be applied? First it turns out that weight estimates for dinos are very tenuous... Be good to know that the years assigned to named periods are at least calendar years, even if their number slides a bit.

**Follow-Ups**:**Re: When is a Year Not a Year?***From:*Dann Pigdon <dannj@alphalink.com.au>

**References**:**When is a Year Not a Year?***From:*"philidor11" <philidor11@snet.net>

**Re: When is a Year Not a Year?***From:*Dann Pigdon <dannj@alphalink.com.au>

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