Simulating the current night sky is easy to do with a star chart or planisphere, which accounts for the time, date, and geographic latitude. But these charts don't work for ancient cultures, because of precession. To go back in time, archaeoastronomers and teachers can turn to personal computers and any of a number of software packages. The shareware Skyglobe operates on IBM-compatible computers; the ASP sells Dance of the Planets (IBM) and Voyager II (Mac) through its catalog. Such simulations can be used to study ethnic groups of the past. For example:
People did not just watch the sky; they evidently tried to communicate to it. The large earthen figures of the British Isles and Peru are huge and difficult to recognize from the ground; perhaps they were constructed for viewing by the gods. Examples include the Long Man of Wilmington, England and the Owl Man of Peru (see figure 8 and figure 9). Although the true intentions of the people who constructed the figures is still a mystery, students can make informed guesses by comparing the figures to images intended by modern scientists for extraterrestrial civilizations.
Long Man of Wilmington, England.
Owl Man of Peru.
Examples of modern messages include:
Students can tabulate and analyze the striking similarities that exist among the modern and ancient images. They could also construct an original pictorial message for extraterrestrial civilizations, explaining why they chose particular symbols. If a nearby football field is nearby, students can map their picture on graph paper and lay it out on the ground.
The Pioneer plaque, designed as a message to extraterrestrial beings. The plaque shows where Pioneer came from and who sent it. The barbell at top left represents the hydrogen atom; the radial pattern at left center shows the position of the Earth with respect to pulsing stars. Photo courtesy of NASA.
Deciphering the unique number system of the Maya is another archaeoastronomy topic that involves a minimum of math. Unlike our modern Arabic system -- 10 digits, strung out horizontally, representing powers of 10 -- the Maya used digits, stacked vertically, representing powers of 20 (see figure 11). Several collections of early writing of the Maya survive; numbers from them can be read and in some cases interpreted (see figure 12). One document, for example, shows the 584-day synodic period of Venus and the associated Maya god, Kukulcan [see "Ancient Astronomy in Mexico and Central America,'' Mercury, January/February 1975, p. 24; "Emissaries to the Stars: The Astronomers of Ancient Maya,'' Mercury, January/February 1995, p. 15]. The synodic period of revolution of a planet is the length of time it takes to return to the same position relative to the Sun, as seen from Earth.
Mayan numerals. A dot means 1, a horizontal bar means 5. These symbols are an abstraction of hand-counting gestures from pre- literate times. The Mayas used base-20 notation, as opposed to our base-10 notation; each Mayan numeral represents a number from 1 to 19. The numerals can be written either horizontally or vertically; the dots appear above or to the left of the bars. The Maya often decorated their numerals and adopted special glyphs for important numbers.
As archaeoastronomers study the calendar of the Maya, they find ceremonial intervals of time that can be related to the year and the synodic period of Venus. These cycles are represented by large, whole numbers; when multiplied by other cosmologically significant whole numbers, they result in a single, very large, sacred number, 37,960.
The Maya Eclipse Table, from the Dresden Codex. There are plenty of numbers to decipher! For example, the arrow points to a number that consists of two numerals. The top numeral, three dots and a bar, equals 8. The bottom numeral, two dots and three bars, equals 17. Since the Mayas used base-20 notation, this number is 8 x 20 + 17 = 177. The number 177 was important in eclipse predictions. Photo courtesy of G. Kohlmann and L. Blanco, CIEA del Instituto Politecnico Nacional, Mexico.
The archaeoastronomy of numerous societies over the millennia shows remarkable similarities and differences in the interpretation of the appearance and motions of the celestial bodies. Worldwide similarities are mostly in timekeeping and the association of a hereafter life with the heavens. The differences are mostly in the ways and times that particular holidays were determined.
In spite of the ancient origin of the diverse ethnic topics of archaeoastronomy, the subject is quite contemporary in character. As the world shrinks with advances in technology of communications and travel, the more we are required to understand the global community and its ethnic diversity.
LOUIS WINKLER teaches astronomy to nonscience students at Pennsylvania State University in University Park. His instruction includes large lectures with numerous computer demonstrations, small laboratories with students operating computers in many activities, and a mathematically founded course in archaeoastronomy.
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