164 calendars and clocks: Africa View of the royal tombs at Meroë, ancient city of northeastern Africa in present-day Sudan; the entrances face east, toward the rising star Sirius, a positioning that suggests that they served as a type of calendar (Courtesy of the Oriental Institute of the University of Chicago) expertise in astronomy, for the progression of days, months, seasons, and years represents the movement and rotation of the earth in relation to the sun and moon Archaeologists who study these matters refer to their field of inquiry as archaeoastronomy These scholars are interested in archaeological evidence of astronomical observations that ancient societies made to keep track of time One of their major findings was the discovery of a calendar system used by the Borana of southern Ethiopia and northwest Kenya The Borana, ignoring the sun, developed a calendar regulated by seven stars and star groups observed in conjunction with the phases of the moon In 1978 archaeologists discovered at a site near Lake Turkana in Kenya a cluster of 19 stone pillars The name of the site is Namoratunga, meaning “stone people.” Writing carved on the stones provides evidence that the pillars date to 300 b.c.e The Borana measured time using a 354-day lunar year with 12 months; they did not keep track of weeks Every three years a leap month was added so that the lunar years remained consistent with the 365-day solar year The Borana relied on seven stars or star groups: Their modern names are Triangulum, Pleiades, Aldebaran, Bellatrix, Orion’s Belt, Saiph, and Sirius The new year began when a new moon was observed in conjunction with Triangulum; the next month began when the new moon was seen in conjunction with the Pleiades, and so on The Borana had names for only 27 days of the month, even though the month could be as long as 30 days; when they arrived at the end of the list after 27 days, they started over with the name at the beginning of the list Astronomers and archaeologists, though, have struggled with how the Borana knew that the specific star systems were near the moon, because some of these stars cannot be seen when they are too close to a new moon Some researchers believe that the 19 Namoratunga pillars were intended to mark the positions of these stars, allowing the stars’ placement in the sky to be known even when the stars themselves could not be seen clearly Using statistical analyses, archaeologists have determined that the possibility is less than a half a percentage point that the pillars could have marked the stars’ locations by chance For them, this is strong evidence that the cluster of pillars was an astronomical observatory and hence a calendar Structures that function like calendars have also been found in other parts of ancient Africa In central Sudan the kingdom of Kush flourished from about 1000 to 100 b.c.e The area features numerous pyramids, similar to the pyramids found in ancient Egypt The entrances to these pyramids face east, directly at the rising star Sirius Th is positioning suggests that they served as a type of calendar In numerous places in Tanzania archaeologists have discovered cave drawings of precisely drawn circles The circles are concentric and exactly spaced The number of circles ranges from one to 29 or 30—numbers that suggest some connection with the lunar cycle Little is known about timekeeping in ancient Africa Like most cultures throughout the world, the ancient Africans probably kept track of time throughout the day with some sort of basic sundial A sundial can consist of little more than a