Talk:Maya calendar/Archives/2006/July

Confusing statement

I think that statement is a confusing attempt at summarizing the Jenkins explanation. (See the Jenkins link at the end of the article).

Let me try to paraphrase Jenkins:

If you look at the stars (or at a map of the stars), the Sun and all the (visible) planets are always found along a straight line on the map called the ecliptic. The Milky Way (as seen in the sky from Earth) lies along another line on the map called the galactic plane. (Some people call the intersection of these 2 lines the "galactic center". But I think the true Galactic Center is somewhere else along the galactic plane, right?) The sun makes a complete circle all the way around the ecliptic every year. The exact day of the year that the sun crosses the galactic plane, however, is very slowly changing. (On that special day, the Milky way points exactly at the sun just before sunrise, and continues to point to the sun just after sunset). Over the past roughly 3000 years, the day the sun crosses the galactic plane has changed from early November, to nearly the winter solstice. In 2012, the sun will cross the galactic plane on the day of the winter solstice.

Jenkins claims that the Maya choose the start date for their long count, such that that long-awaited, never-seen-before event (the "special day" of the sun crossing the galactic plane, and the day of the winter solstice, both occuring on the *same* day) will occur on the end date.

Does that make sense? Is this worth moving into the article? —The preceding unsigned comment was added by 70.189.75.148 (talk • contribs) 20 Nov 2005.

No one can observe the Sun crossing the Galactic plane because the Sun is too bright. Indeed, you cannot even observe it just after sunset. The Sun must be at least 18° below the horizon for the Milky Way to be seen at all. Nor can any stars be observed near the Sun. The typical link used by pre-modern astronomers was the Moon—as the Sun is setting, the full moon is rising (both have a refraction error of 1/2° and the full moon has a parallax error of 1° compared to their meridian positions). But even a full moon is too bright to observe the Milky Way, only bright stars are then visible. The Moon must be below the horizon to observe the Milky Way. Thus the Milky Way is twice removed from Sun: Sun → Moon → bright stars → Milky Way. The point here is that any error in the speed of the Sun along the ecliptic will be compounded by any error in the speed of the Moon, which does not even follow the ecliptic, but can deviate from it by up to 5°.

Based on about 400 years' worth of written observations, the Babylonians had a highly accurate value for the average speed of the Moon, but although they knew that its speed was highly variable, they could not assign any decent value to it. The first to offer any reasonable value for these variations was Ptolemy, and his values were off by several degrees. Not until about 1750 did anyone develop resonably accurate (within a fraction of 1°) predictions for the true position of the Moon.

The ancient Egyptians thought the sidereal year was 365 1/4 days, if we are to believe that they knew of the Sothic cycle, which is far from certain. Their calendar, like that of the Maya Haab calendar, used a year of only 365 days with no leap days at all. But the 365-day Haab is a later creation than the Long Count—only the 260-day Tzolkin is contemporaneous.

To find the length of the tropical year, we must subtract precession from the sidereal year. But Jenkins offers no evidence whatsoever that the Maya knew of precession. But even if they knew of it, there is no way that they could have had an accurate value for it. Both Hipparchus and Ptolemy underestimated the speed of precession by about 40%, by far the worst 'accuracy' of the three required speeds. They thought an equinox would move 1° every century, whereas its true value is about 1° every 72 years. Both Hipparchus and Ptolemy assumed that a tropical year (which includes precession) was 365+1/4–1/300 days long. We can use Robert van Gent's Almagest Ephemeris Calculator to determine when Ptolemy would have placed the winter solstice of 2012. The result is near midnight Maya time at the beginning of 16 December (Julian) or 3 December (Gregorian). So if the Maya had Ptolemy's knowledge and all of his errors and ideosyncracies, they would have placed the epoch of the Long Count about 19 days earlier than they did to make sure that it ended on a winter solstice. I doubt that Ptolemy assigned any plane or great circle to the Milky Way, so was probably not able to calculate when the winter solstice would cross it to an accuracy of a year.

David Ulansey has the conjunction of the winter solstice, ecliptic, and galactic equator occurring 21 December 1999. Another view on the Maya conjunction, admitting that it is 12 years late according modern Galactic coordinates, is that by Alias Jones. Still another analysis by Shepherd Simpson stated that the conjunction occurred 21 December 1997. Finally we have another New Age astrologist/philosopher (like Jenkins), Carl Johan Calleman, who destroys Jenkins' arguments, partially using Jenkins' own words, for Jenkins himself stated that the end of a one fifth precession cycle (5125 years) occurred 12 December 1998 and that the conjunction occurred 12 December 1999, in agreement with modern astrologists and astronomers (Jenkins obviously ignored his own statement to arrive at his 2012 conclusion). A major part of Calleman's criticism is that Jenkins totally ignores the Maya Creation stories, which describe the events near 3114 BC, not those near 2012.

Jenkins does not even mention most of the lunar and solar positioning errors, asking us to believe that the Olmec (who developed the Long Count several centuries before the Maya adopted it) had knowledge that not even the Old World had until several centuries later. But that is insufficient—the Olmec must have had precise modern knowledge of all astronomical calculations in order to predict the winter solstice with an accuracy of a single day over two millennia later. I reject that as utterly preposterous. The end point of the Long Count being at a winter solstice is pure coincidence. Even if we surmount this insurmountable barrier, precession is so slow and the Milky Way so wide that any winter solstice in a 30-year period (about 1/2 degree) can be chosen as the Sun's arrival at the Milky Way, depending solely on the discretion of the astrologist.

— Joe Kress 01:11, 22 November 2005 (UTC)

Joe, a masterly demolition, very nice work. I had in mind to register my own objections, but these are now rendered superfluous. It only remains to add that despite his namedropping of reputable scholars like Schele and Lounsbury, Jenkins is himself neither credible nor accredited in this field, one of many such "enthusiasts". Apart from where he has pestered Mayanists on some Usenet groups, no-one has taken a blind bit of notice of his theories, and as such they do not really warrant mentioning here, even as an example of erroneous but widely-circulated interpretation.--cjllw | TALK 03:14, 22 November 2005 (UTC)

Jenkins does get one fact right: He states that the epoch of the Long Count was in 3114 BC—most Maya scholars insist, or used to insist, that it occurred in 3113 BC. This is because they included a year zero between BC and AD. See, for example, Linda Schele, The proceedings of the Maya hieroglyphic workshop (Austin, Texas, 1992) page 173. — Joe Kress 06:17, 10 December 2005 (UTC)

Joe: There are two methods of calculating negative years - historical and astronomical. In historical the year 1BC is followed by the year 1AD. In astronomical dating there is a year -1 followed by zero followed by 1 so -3113 is the same as 3114BC. 19:34, 8 July 2006 (UTC)Tlaloc

While I seriously doubt the Maya knew the relative movements of astronomical bodies with greater accuracy than modern astronomers (because you'd expect to find remnants of the technologies needed to keep such accurate tabs in addition to evidence of knowledge of predictive physical theories), there is no reason to believe that they didn't know more than "Old World" astronomers--they were working with the same technology (the time they were making these observations is irrelevant, since they were independent societies. It is quite concievable that the Olmecs refined the art of astronomical observation long before Ptolemy, I don't know why you think its so ridiculous). Of course there is ALSO no reason to believe that they did know more accurately the relative movements. But nonetheless your argument that because "Old World" astronomers didn't have a very accurate view so therefore the "New World" astronomers couldn't have surpassed them doesn't hold a bit of water. It is possible that the Olmecs knew some tricks that "Old World" astronomers didn't. I'm not saying they did, I'm just saying "its possible", and your implicit assumption that the ancient "New World" astronomers must have had atleast as much inaccuracy as the "Old World" astronomers is completely unwarranted.

If you were to make a good upper limit argument on thier accuracy it would have to start from assumptions about the technology they likely had to work with and thier knowledge of physics. It might be safe to assume they didn't have glass grinding technology, and therefore no telescopes (and even if you allowed for that, it would be safe to assume it wasn't incredibly accurate glass grinding technology, because glass doesn't appear to be a technology that was widely used enough for archaelogists to have found some remnants of it). Likewise there is no apparent knowledge of say relativititic effects. With those two assumption you could find some upper and lower limits of the accuracy of thier measurments and predictions. But NOT by comparing them with "Old World" astronomers. Brentt 00:55, 7 July 2006 (UTC)

Brentt: Ancient Mesoamerican astronomy was based on the azimuth of the rising and setting of heavenly bodies so your speculation that they might have had more accurate data than later old word astronomers is wrong. You can read about this in Anthony Aveni's classic book which is listed in the bibliography. Also it is unnecessary for you to put so many terms in quotes. 19:34, 8 July 2006 (UTC)Tlaloc

All I was sayign is that what Old World astronomers did was completely independent of what mesoamerican astronomers did. The relative times they did it is irrelevant to. What is relevant is thier methods, Ptolemy's and Hipparchus's method's are completely irrelevant to mesoamerican methods. The methods themselves will provide upper limits on accuracy, and you can't glean any information about thier methods from Old World methods (atleast not that you couldn't glean from the methods themeselves). I didn't mean that speculataion in any more than a trivial sense. (like "its possible they were the descendents of the Great Spahgetti Monster") The point was that what Ptolemy did had nothing to do with what the Olmecs or Maya did. Brentt 22:52, 8 July 2006 (UTC)