Zimbabwe Ruins Ancient Observatory?

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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