[Aztlan] AD or CE? (additional note on BP)

[Robert Hall]

To further complicate the AC/BC//CE/BCE//BP picture, 2000 years before AD 1950 is actually astronomical -50, which is 51 BC, when the year zero is taken in consideration. This is almost never the way the C-14 dates are rendered for print purposes, because dates BP when published are usually rounded to the nearest 5 or 10 years anyway, so as not to give the impression of greater precision than actually exists. Note that Eric Thompson has given the 13.0.0.0.0 4 Ahau 8 Cumku Maya era base date as in a year 3113 BC, for example, as in his book The Rise and Fall of Maya Civilization, rather than as in 3114 BC, using some similar convenience or understanding.  Bob Hall

--- On Sat, 8/22/09, David Hixson <aztlandave at yahoo.com> wrote:


From: David Hixson <aztlandave at yahoo.com>
Subject: Re: [Aztlan] AD or CE? (additional note on BP)
To: "Mario F. Malo" <troycabo at yahoo.com>
Cc: aztlan at lists.famsi.org
Date: Saturday, August 22, 2009, 8:47 AM


Not to add any confusion to this thread, but some listeros might see archaeologists or geologists use the abbreviation BP.
 
Unlike AD, BC, CE, and BCE, a date given as BP is based upon radiometric measurements, and stands for "Before Present".  However, "Present" is defined as 1950 (approximately when the first radiocarbon dates were published, and roughly when the world's natural cycles of atmospheric radiation were thrown off by nuclear explosions).  So, if you see a date that is marked as "BP" (or hopefully "cal BP", indicating a calibrated or calendrical radiometric date), subtract that number from 1950.
 
Examples -
2000 BP = 50 BC (or 50 BCE)
1000 BP = AD 950 (or 950 CE)
 
Please note that the moderators of Aztlan accept all of the notational systems above, and do not ask our list members to use one or another.  Therefore threads like this one are important to post from time-to-time so that all members can read, understand and enjoy posts authored by individuals who may utilize such abbreviations.  Thanks for the question, Mario.
 
-Dave
_______________________________________
David R. Hixson
Aztlan Co-Moderator




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