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To: Publius6961; graycamel; ProtectOurFreedom; socal_parrot; ArrogantBustard
[My professors use "B.P.", meaning "before present".]
Now, there's a useful scale. Changes every day.

No it doesn't, since the "BP" scale is measured relative to 1950. And there's nothing PC about it, it was established for practical reasons:

1. So that there would be a single scale for historic measurements. Using AD/BC can be error-prone, since a typo or inadvertently dropping or overlooking the AD/BC designation can throw off results by 2000 years.

2. So that all dates would be on a single scale where all figures are positive numbers, removing the need for error-prone conversions. For example, it's too likely to look at "AD1000" and "1500BC" and think they're 500 years apart if you're not paying enough attention. This is one reason why physicists often prefer the Kelvin temperature scale, where all possible temperatures are positive numbers -- on either the Celsius or Fahrenheit scales, some temperatures will be positive and some will be negative. The AD/BC convention has another calculation complication in that there was no "year 0". AD5 and 5BC are 9 years apart, not 10. On the BP scale, on the other hand, years X and Y are exactly X-Y apart -- quick and easy.

3. Even more importantly, BP dates are usually relative and not absolute, since they most often derive from Carbon-14 or other dating methods. Using "BP" is an implicit reminder that the dates most likely have an "error bar" on them. 3000BP most likely means something like "3000 years before 1950, give or take a few years", whereas the equivalent 1051BC gives the false impression of a precisely known historic calendar date.

4. The majority of BP dates are far enough in the past that the AD/BC designation starts to become irrelevant anyway -- for example 750,000 years BP is long enough ago that it's 748,051BC, which still rounds out to 750,000 any way you look at it.

5. Why 1950? Because the first radiocarbon results were published in December 1949, so the first day of 1950 seemed a good "year zero" for radiocarbon results to be calibrated to so they could be compared and reported consistently. Otherwise you get the "museum guide problem":

Museum guide: "This fossil is 65 million and 4 years old."
Museum visitor: "Wow, how did they date it that precisely?"
Museum guide: "Well, it was 65 million years old when I first came to work here four years ago."
Another common term for times on a geologic timespan is "MYA", or "millions of years ago".

Where do these doofus losers come from anyway?

Unfortunately, it seems that some of them come from FreeRepublic.

78 posted on 11/18/2004 12:13:14 PM PST by Ichneumon
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To: Ichneumon
AD5 and 5BC are 9 years apart, not 10.

That depends on what dates you are speaking of. A year is a span after all, not a point. Jan 1st 5 BC and December 31st 5 AD are indeed ten years apart.

88 posted on 11/18/2004 12:30:57 PM PST by FreedomCalls (It's the "Statue of Liberty," not the "Statue of Security.")
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