Viewers of the total solar eclipse in Southern Africa recently have also had their eyes opened by a 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.
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.
"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.
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.
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
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