The Egyptian town of Mallawi is not on the main tourist beat, given its location 260 miles and a seven-hour train ride north of the temple complexes at Luxor. But one of us (Symons) traveled there in May 2013 with Robert Cockcroft, a postdoctoral researcher in her laboratory, hoping to see one of the oldest astronomical records in the world. The record, which had been described only vaguely, was indeed there, but to their astonishment, it was not the only one.
“I can see writing!” Cockcroft exclaimed. At that moment, he was crouched beside a display case that enclosed a coffin in the central room of the Mallawi Monuments Museum, craning his neck to peer at the underside of the propped-up wood lid. Symons flicked the beam of her flashlight to illuminate a thin batten—a cross piece—that held the flat panels of wood together. The batten's surface was painted with graceful hieroglyphics representing star names, and Symons and Cockcroft immediately realized that the cross piece was part of yet another ancient astronomical record. Until that moment, no one had recognized the batten's significance; it had been attached to this particular coffin by mistake.
Archaeologists first began discovering these intriguing coffin records in the 1890s while exploring tombs in the nearby burial complex at Asyût. After opening up certain rectangular caskets that held the mummified remains of local nobility, the explorers found very specific designs on the inside lids instead of the plain wood or the extracts from religious texts seen in most ancient Egyptian coffins. These special drawings depict an organized table of star names, recording the movements of selected stars, such as Sirius, throughout the year.
As a historian of science, Symons has spent the past 20 years cataloguing and analyzing these astronomical tables. Depending on how one counts certain fragments, only 27 have come to light, of which just one is not from a coffin: it adorns the ceiling of a temple. Most of the tables date from about 2100 B.C. By examining these and other ancient hieroglyphics and taking advantage of sophisticated planetarium software, she hopes to reconstruct how and why the Egyptians developed the tables and discern the observational methods used to construct them. Her work so far casts doubt on the prevailing view of why Egyptians of the Middle Kingdom period constructed the charts and may ultimately help clarify what these Egyptian astronomers did and did not know about the stars that filled their skies.
The excavators who found the charts knew that they depicted stars, but not until the 1960s did anyone put forward a comprehensive hypothesis to explain what the tables may have represented and what their function was. In a three-volume work entitled Egyptian Astronomical Texts, science historian Otto Neugebauer and Egyptologist Richard A. Parker described the 13 tables that had been recovered by that time and proposed that they traced the order in which selected stars (or small clusters of stars) first rose over the eastern horizon during the nights of each week throughout the year. They speculated this information was recorded to tell the time during the night. Someone noting which star was on the horizon at any given moment would have a sense of how much time had passed since sunset, and so Neugebauer and Parker referred to them as star clocks.
Such clocks, if they were also available somewhere other than the hidden surface of coffin lids, could have been important to priests of the time. According to Egyptian mythology, the sun undergoes a dangerous journey during the night, when it must overcome multiple obstacles. By performing specific rituals at key moments during the dark hours, priests could mirror the sun's journey and provide assistance.
Neugebauer and Parker's description of the star tables was certainly consistent with such a use. A complete table is divided into quarters by a horizontal and a vertical strip. The horizontal strip contains a line from a religious text making an offering to a number of Egyptian gods, and the vertical strip pictures four images of the gods themselves. What drew Neugebauer and Parker to the idea of a clock is that running along the top of the table is the ancient Egyptian civil calendar.
Each month in the ancient Egyptian civil calendar contained three 10-day weeks; 12 months followed by five days make up the 365-day year. A complete star table, read from right to left, consists of 40 columns, where the first 36 columns each denote one “week.” The next three columns show a complete list of all the names of stars described in the chart (represented by the numbers 1 through 36), and the final, 40th column represents the remaining half week in the civil year. Because a different star heads the top of the column corresponding to each 10-day week, the stars are today called decans, from the Greek word deca, meaning “ten.”
Every column of decans consists of 12 rows, where the vertical placement, Neugebauer and Parker argued, reflects the order in which the decans appeared over the horizon in the night sky. (Thus, each row represents a different “hour” of the night.) The topmost cell contains the name of the decan that rises in the east shortly after the sun sets. (In the sky, the star then moves west across the sky as the night progresses.) The next 11 decans then rise behind it in the order they are listed down the column. Ten days later, week two of the civil calendar begins, and the sky has changed; now a different decan—decan 2—rises with sunset, so it appears at the top of that week's column. The result is a diagonal pattern of decans, where the same decan moves in a diagonal line from bottom right to top left as it rises steadily earlier over the year.
If the year were exactly 360 days, the pattern in the star charts would form a seamless cycle of 36 decans. After the 36th decan had risen in the night sky, the first decan would reappear behind it the following week. The half week of the remaining five days in the year prevents this procession, however. To cope, Neugebauer and Parker concluded, the ancient Egyptians recorded the motions of an entirely new decan set. As these new decans marched diagonally up the table, they collectively formed a triangular shape at the left-hand side of the table.
In schematic representations of the tables, researchers label the triangle decans differently from the others—with letters, rather than numbers. But the drawings on the coffins themselves give no indication that the Egyptians considered the triangle decans to be of more or less importance than the other 36 decans. Other astronomical depictions on temple and tomb ceilings (of a design that is probably contemporary with the coffin tables), however, made the distinction, which has led to debates among Egyptologists about which came first—the idea of 36 “perfect” decans processing regularly across the sky from east to west or the actual observations of various real stars in their more complex annual journeys.
In any event, the presence of the triangle confirms that the tables are the result of real astronomical observations. The extra level of complication introduced by the additional decans argues against the tables being simply an idealized model of the cosmos.
Despite the elegance of Neugebauer and Parker's explanation of what the charts showed, their scheme left a number of big questions. One problem, recognized in the 1960s by Neugebauer and Parker themselves, was raised by the realization that the star tables they knew about were not all alike.
To the untrained eye, the format of all tables looks identical, with a layout of ordered columns populated by many of the same decan names. A closer comparison, however, reveals that they fall into two major groups in which the decans are shifted by several columns. Neugebauer and Parker suggested that the variance stemmed from the absence of a leap-year system in the civil calendar. If ancient table makers, ignoring the extra quarter day a year, made two tables 40 years apart, 40 quarter days of slippage would mean the later table had star positions shifted by exactly one 10-day week, or a movement of one cell per decan. Neugebauer and Parker assumed that if more star tables or related documents were uncovered, examples of layouts in between the then known groups would appear.
But work by Symons raises doubt about this thesis. She has studied directly or examined photographs of all the known star tables, including ones discovered after the 1960s. Every one falls into one of the two groups now accepted by Egyptologists, with none showing an alternative pattern of decans. Moreover, the separation between matching pairs of decans varies; a leap-year progression would move all decans together and preserve their spacing.
Neugebauer and Parker also could not be certain that the charts actually tracked the rising of stars on the horizon, as their scheme suggested. Symons's analyses have revealed some alternative possibilities that seem equally feasible. Her clues come from inconsistencies between the two table types that go beyond decans shifting their columns. The order of appearance of some decans, for instance, differs as well, and she has some tools at her disposal that Neugebauer and Parker did not.
Symons has access to powerful planetarium software that can roll back the millennia to display the night sky above ancient Egypt. When we look at the night sky today, Earth's axis of rotation points approximately at the star Polaris. But the axis actually wobbles very slowly in a circle about every 25,800 years. Therefore, although the overall behavior of the sky has not changed (the sun still rises in the east and sets in the west) and the relative positions of the stars to one another has not changed, the wobble means that everything in the sky is in a different place as compared with where it was 4,000 years ago.
Having an accurate, moving view of the ancient sky can help offer explanations that are otherwise hard to visualize. Researchers can describe the old positions of the stars mathematically, but the equations are long and complex. A computer model performs the calculation automatically, at the click of a button.
As the planetarium software helps to make clear, the inconsistencies between the two groups of tables can most easily be explained if the stars were observed using two different methods. The computer simulation shows that all stars that rise at the same time along the eastern horizon—as viewed from anywhere in Egypt—will set at different times on the western horizon because of Earth's tilt relative to the celestial sphere. This feature of stellar movement would serve to distort or even jumble the order of decans somewhat if a table tracked the setting of decans; the movement seen in the two different types of star tables is consistent with one set representing the rising and the other the setting of stars.
Planetarium software can also be used to check other possibilities and eliminate ones that do not work. An alternative explanation for the differences between the two groups of tables could be that the stars were being observed from two different locations within Egypt. Comparing planetarium simulations at different latitudes with the real tables strongly suggests that this was not what happened. Observations would have to have been made at the far northern coast of Egypt and deep into the extreme south for the latitude of these observations to make enough of a difference to match the surviving tables.
Simulation has its limits, however. The rising-and-setting scenario works, but so do variants, such as imagining that the “horizon” used was not the natural horizon but the edge of a wall or a point above a particular tree. The models, for all their computing power, can only mesh with the available data and are therefore best suited at present to excluding possibilities rather than attempting to “prove” what actually happened.
The same limitations apply when trying to use planetarium software to identify which stars in our own sky the ancient decan names represent. So far computer simulations have confirmed that one of the decans was the star Sirius (transliterated from the hieroglyphs as spdt and pronounced and written as Sopdet), the brightest star in the sky then as now and an important celestial object in Egyptian astronomy. A few people have come up with plausible identifications of other stars that were monitored, but the level of confidence varies from decan to decan.
Most researchers think that the decan Khau denotes the Pleiades, a supposition that is supported by the software as well. Tjemes en Khentet is probably a red star because tjemes means “red”; that phrase and the location of the decan in relation to Sirius/Sopdet, the computer program shows, are therefore consistent with Antares. Beyond those fairly obvious deductions, however, any historian of ancient Egypt could argue for this star or that and not agree with the opinions of others, because each researcher would have different ideas about what the Egyptians would have used as their criteria for selecting a star to be a decan. Where precisely in the sky should we look to see the rising of a star? Due east? Within five degrees of east? Within 10 degrees? Would a star that was bright and familiar but not in exactly the right position have been chosen over one that was more obscure but rose or set in exactly the right spot for table-making purposes?
Ultimately, if we knew more precisely which stars were used, we could deduce the observational procedure. If we knew the observational procedure, we could guess the stars. The fact that we know neither leaves us having to make assumptions.
Perhaps even more fundamental than the issues raised by having two types of tables is the question of their purpose. As mentioned, Neugebauer and Parker viewed the tables as clocks. The term implies a system akin to modern timekeeping: the tables are an instrument, with a focus on accuracy and a precise delineation of time. This view is inconsistent, however, with the Egyptian treatment of the passage of time generally. Although people in the 21st century consider time as the abstract passing of regular hours, minutes and seconds, the ancient Egyptians did not. Instead, events such as the celestial motions of the sun or stars determined the time of day or night. Midnight or dawn, for instance, would be periods when certain stars were visible or the sun was in a particular region of the sky rather than a single, well-defined instant.
This aspect of the culture runs counter to the view that the charts were developed as a way to keep time accurately, and so the more general term “star tables,” rather than “star clocks,” now seems more apt. In addition, planetarium software shows that the ancient sky did not always have a bright star exactly where and when you would need one. Furthermore, the stars cannot be seen at all until the sky is dark enough. Overall, the “hours” told by a star clock would be shorter than 60 minutes and would probably be quite irregular. Symons's current view is that the tables are more like almanacs or charts, recording the state of the sky over time, than they are like practical clocks.
Of course, the obvious remaining question is, Why are the star tables found primarily inside coffins? And why did dead people need to tell the time? Did they need to know how the sky moved?
The probable answer has a lot to do with ancient Egyptian beliefs about the afterlife. Temples, tombs and even coffins were model worlds in which the ceiling or inside lid represented the sky. Furthermore, even some of the earliest religious writings, the Pyramid Texts, contain the notion that souls can be reborn as stars. After death, a pharaoh was thought to become part of the circumpolar stars whose proximity to the northern celestial pole means that they never rise or set; they are immortal stars. Later thinking could have extended this vision to allow other notable individuals—such as the local gentry around Asyût—to rise as lesser stars whose paths dipped below the horizon at different times of the year. In such a case, the deceased might need the star table to guide them as they rose to join the decans.
Digitizing the past
To facilitate further research into the function of star tables, Symons has developed an online database that now contains the information found in all the known examples. This compilation provides researchers with a common base of knowledge for further study and negates the need to maneuver, and thus potentially damage, the fragile coffins.
There is some hope for finding additional tables. New specimens occasionally turn up in archaeological digs in Egypt. Unfortunately, the existing relics are not necessarily secure. Several weeks after Symons and Cockcroft's visit and the discovery of the new fragment, for instance, the museum in Mallawi was looted as part of the civil strife in 2013. Although a number of objects have since been recovered, the current status of the star tables is unknown. Returning to Egypt this year, Symons and Cockcroft were, however, able to complete their survey of the star tables in other Egyptian museums and will continue to document and analyze the astronomical heritage of ancient Egypt. Each new fragment brings additional insight and the possibility of a breakthrough in our understanding of the ancient astronomers' work. All the more reason to carefully preserve what we have and to continue searching for more.