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Q: Mayan Calendar ( Answered 5 out of 5 stars,   0 Comments )
Subject: Mayan Calendar
Category: Science > Social Sciences
Asked by: toluca-ga
List Price: $10.00
Posted: 28 Jan 2003 13:49 PST
Expires: 27 Feb 2003 13:49 PST
Question ID: 149655
What is the basis for the accepted correspondence between the Mayan
calendar and the Gregorian calendar? I know that there is an accepted
correlation called the Goodman-Martinez-Thompson based on astronomical
events, but which specific events and dates is that based on?
Subject: Re: Mayan Calendar
Answered By: robertskelton-ga on 28 Jan 2003 20:14 PST
Rated:5 out of 5 stars
Hi there,

From my own (lesser) studies of the Mayan calendar, I already knew
that the GMT correlation somehow involved eclipses, which could be
pinpointed in both Mayan calendars and historical documents in the Old
World. Thanks for motivating me to look deeper into the correlation
evidence that exists.

The GMT correlation is the most accepted, because it is the best fit,
although not perfect. In his book "Maya Cosmogenesis 2012", John Major
Jenkins says:

"Significantly, of all the proposed correlations, the GMT is the only
one validated by both carbon-14 dating and that fact that it is
synchronized with the surviving Quiche Maya count."

(He had the common sense to actually visit Mayans who still use the
ancient calendar and ask them what day it is!)

I have found a very well written article that covers your question.
Although I quote the most pertinent sections below, I recommend
reading the complete article.

Age of the Moon

The Long Count is the main yard stick for correlating calendars,
because it runs for 5125 years. Long counts in Mayan inscriptions are
often followed by the age of the moon. A monument from Qurigua dated 4 Ahaw 13 Keh correlates to September 15, 795 AD

NOTE: "There are also frequent discrepancies between lunar ages and
their predicted correlations, but most result from errors in the
inscriptions themselves.  By studying sequences of lunar dates on
monuments from Copan and Palenque, Teeple showed that the lunar ages
recorded by the scribes were often based on calculation rather than
observation. For example, it appears that the scribes sometimes used
the formula 6 lunar months = 177 days to date new moon from earlier
observations.  Since 6 lunar months is actually 177.18 days, this
calculation accumulates an error of about 1 day over 3 years. 
Although the scribes also knew more accurate approximation formulas,
we cannot expect all the lunar ages they recorded to agree exactly
with the GMT or any other correlation.  What is possible is a
statistical check on the GMT correlation.  The average error if the
GMT correlation is correct to about 3 days, about as close as could be
expected. "

Full Calendar Round Date

"Matching a full calendar round date is even more difficult. Lounsbury
found that there is only one 1 Ahaw 18 K'ayab in the Classical or
post-Classical  periods which was a helical rise date of Venus if the
GMT correlation is correct.  On 1 Ahaw 18 Kayeb = 25
November 934 AD ('85 correlation constant), Venus was within 0.1 day
of helical rise.  Equally important, this date is exactly 196 Venus
cycles of 584 days after the entry date recorded in the
codex.  Lounsbury suggests that this was a "unique event in historical
time". He believes it was the date on which the Venus table was

Alignment: Mars, Jupiter, Saturn and the Moon

"Perhaps the most remarkable example is found in the glyphic record of
the dedication ceremonies of the temples of the Cross Group at
Palenque. These rituals fell within a four day period commencing 2 Kib 14 Mol , July  23 690 AD if the GMT correlation is
correct.  On this date,  Mars, Jupiter, Saturn and the Moon were
separated by intervals of less than 5 degrees. According to Dutting
and Aveni,  "[On 23 July 690 AD] all four planets were close together
(a quadruple conjunction) in the same constellation, Scorpio, and they
must have made quite a spectacle with bright red Antares shining but a
few degrees south of the group as they straddled the high ridge that
forms the southern horizon at Palenque".  This astronomical event
appears to be recorded in the inscription, which recounts that the
wayob (spirit companions) of  the gods known as the Palanque triad 
were "in conjunction" on 2 Kib 14 Mol. "

Helical rise of Venus

"Lounsbury argued that 1 Ahaw 18 Kayeb was such an event.
It corresponds exactly to the helical rise of Venus on November 25,
934 AD only if the '85 correlation is adopted. However, as Aveni has
noted, naked-eye observation of helical rise is fraught with
difficulty. Venus is lost in the glare of sunrise at the instant of
helical rise. Much depends on atmospheric conditions and the acuity of
the observer, but Venus is usually not visible until several days
after true helical rise, when it is about 10 degrees from the sun.
Lounsbury assumed that Venus becomes visible 4 days after true helical
rise, but if it was glimpsed earlier in 934 AD, the helical rise date
might match the '83 or '84 correlation rather than the '85

Partial eclipse 

"Michael Closs has pointed out that a partial eclipse visible in the
Yucatan on January 24, 771 AD was recorded on Stela E at Quirigua. The
long count date is a period end, 13 Ahaw 18 Kumk'u. Closs
believes this is the only instance of a eclipse occurring on a katun
end in the Classical period, which likely gave it particular
significance. The long count correlates exactly to January 24, 771 AD
if the '85 correlation is adopted. Certainly, this eclipse is strong
evidence in favour of the GMT correlation. But does it confirm the '85
constant?  Closs continues to be convinced that the '83 constant is
correct. Perhaps the occurrence of an eclipse within  2 days of period
end was enough for the scribes at Quirigua to associate the eclipse
with the end of the katun. "

Notes on GMT and Astronomy

"Astronomy did not play a  role in arriving at the GMT correlation,
but Thompson and Teeple turned to astronomy to confirm it. Classical
monuments sometimes give the long count dates of astronomical events.
The Dresden Codex, a post-Classical glyph book, assigns long counts to
a table of eclipses and a table of the apparitions of Venus.

However, astronomy does not provide the kind of unequivocal evidence
many had hoped for, and most competitors to the GMT correlation have
been based on interpretations of Maya astronomy. Some of these are on
the remotest fringes of scholarship. Others, such as the Bohm and
Wells-Fuls correlations, are based on careful argument.  But there is
an inherent  problem in any correlation theory that depends primarily
on astronomy. Maya astronomy was concerned with augury, ritual, and
mythology. There are still gaps in our understanding of the way the
scribes used astronomy. Thus, for example, critics are troubled by the
fact that the base date in the Dresden Codex Venus table appears to be
in error if the GMT correlation is correct. However, this date is
actually several centuries before the Codex was compiled, and was
likely never used as a practical base date for calculating the helical
rise of Venus. It may have been included for ritual or augural
purposes we do not fully understand."

"Unlike correlations based on astronomy, the GMT correlation is not
contrived to force a fit with the eclipse table or other astronomical
data. Thus the eclipse table offers an independent check on the GMT
correlation. The eclipse table does not unequivocally prove the GMT
correlation is correct..."

"The limited power of astronomy to unequivocally settle the
correlation question has not prevented it from being used to erect
alternative correlation theories.  Nor has it prevented advocates of
the GMT correlation from attempting to use astronomical data to choose
between the three GMT correlation constants. What is needed is a
"smoking gun", a unique astronomical event with a clear long count
date. But the smoking gun is difficult to find. "


All the above quotes come from this article:
The Correlation Question, by Michael John Finley

Search Strategy: "GMT correlation" eclipse

Best wishes and fingers crossed for 2012,
toluca-ga rated this answer:5 out of 5 stars

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