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Re: When is a Year Not a Year?

At 5:37 PM -0400 7/8/02, philidor11 wrote:

(Radiocarbon years do not equal calendar years because the amount of radiocarbon in the atmosphere through time has not been constant; it varies as much as 15 percent, making radiocarbon time older or younger than calendar time. In the case of Clovis, a radiocarbon age range of 11,000 to 11,600 years is actually about 13,000 to 13,500 calendar years. All dates in this article are in radiocarbon years.)

And I wonder if the same ratio of difference (11,300/13,250) applies to all dates used. Clarifies my mind.
Anyway, when we get substance-based dates for dinos, can I assume they are calendar years, or should I do an equivalent to my meters-to-feet conversion calculation?

Other radioisotope years are "real" years. The problem with radiocarbon dates is that the radioactive carbon-14 is produced by high-energy particles hitting the upper atmosphere and causing nuclear reactions that produce the radioactive isotope. The charged particle flux varies over time. "Radiocarbon years" are calculated on the assumption that radiocarbon production is constant, so they're a first approximation. Conversion tables have been developed that can convert those radiocarbon dates to real calendar years, which are more meaningful, but there's no simple conversion formula because the radiocarbon production varies quite a bit, with no simple relationship available. (Archaeologists can calibrate with tree ring and ice core data, for example, because they record each year in a countable way.) -- Jeff Hecht
Jeff Hecht, science & technology writer
jeff@jeffhecht.com; http://www.jeffhecht.com
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