Zimbabwe Ruins Ancient Observatory?

04-18-2004, 01:03 PM

Eclipse brings claim of medieval African observatory
NewScientist.com news service
Great Zimbabwe is a controversial site thought to have been a royal
residence (Image: Corbis)

Viewers of the total solar eclipse in Southern Africa early on
Wednesday have also had their eyes opened by second startling event -
newly released evidence that a medieval African site was an
astronomical observatory.

Starting just before 0600 GMT, the shadow of the Moon took 30
minutes to cross Africa from west to east, before heading over the
Indian Ocean to make landfall in western Australia around 0900 GMT.

In Africa, between 0610 and 0620, the shadow crossed the southern
tip of Zimbabwe, not far from the mysterious stone ruins of Great
Zimbabwe, from which the country took its name.

Great Zimbabwe, built in about 1200 AD is a perplexing UN world
heritage site. At its heart is the Great Enclosure - a wall
comprised of over 5000 cubic metres of stone and marking a perimeter
240 metres in length. Archaeologists had assumed it was once a royal
residence.

But on Wednesday, archaeologist-astronomer Richard Wade, of the Nkwe
Ridge Observatory, South Africa, presented his new evidence. He
claims Great Zimbabwe was similar in function to Stonehenge in
England, though much younger.

Eclipse predictor

"This is the culmination of nearly 30 years of research," Wade told
New Scientist. Central to his conclusion is the location of stone
monoliths on the eastern arc of the Great Enclosure.

According to Wade, they line up with the rising of the Sun, Moon and
bright stars at certain, astronomically significant times of the
year. One of the more striking alignments that Wade has observed is
the rise of three bright stars in Orion over three of the monoliths,
on the morning of the winter solstice, the shortest day of the year.

The patterns have previously been interpreted as those on snake
skin (Image: Natural History Museum, Bulawayo)

One monolith could also be an eclipse predictor. Wade says it is
notched in such a way that "the pattern and amount of notches can
only be a record of the Venus' alignments with Earth, and we know
that the location of Venus in the sky can be used to predict
eclipses. It also has crescents and discs carved into it."

Perhaps most contentiously, Wade believes he knows why a conical
tower that has previously baffled archaeologists was built. "The
conical tower lines up precisely with the supernova known to have
exploded in Vela, 700 to 800 years ago," he says.

Chance alignments

His work so far has been vetted by astronomers from the South
African Astronomical Observatory and will be submitted to scientific
journals.

However, some experts warn that there are so many stones on the
walls of the Great Enclosure that some chance alignments are
inevitable. Researchers should be careful of reading too much into
them, they say, adding that more work is needed before Great
Zimbabwe's use as an observatory is proven.

David Dearborn, a physicist at Lawrence Livermore National
Laboratory who has also studied Mayan astronomy in South America,
notes that spectacular sites like Great Zimbabwe and Stonehenge pose
a particular scientific challenge because they are one-offs.

Astronomical alignments of objects at such sites may be suggestive
but chance cannot be ruled out. Dearborn adds that studies of
numerous smaller sites can provide statistical support for such
alignments, as can evidence from oral histories that people who used
the site had astronomical knowledge.

Stuart Clark and Damian Carrington
http://www.newscientist.com/news/news.jsp?id=ns99993137