This study re-examines the use of star clocks, or diagonal star tables, in ancient Egypt. By digitally reconstructing the night sky as seen from specific locations and times in Egypt, the researchers demonstrate how these tables functioned. Each table tracked fifteen decanal stars, marking the passage of time throughout the night by their sequential risings and culminations. The study reveals a continuous tradition of star clock use spanning multiple dynasties, with tables adjusted for precession. It also highlights regional variations and potential administrative uses of these astronomical tools, solidifying their importance for timekeeping in ancient Egyptian society.
The ArcGIS StoryMap titled "An Astronomical View of Ancient Egyptian Star Clocks (2021)" presents a compelling exploration of how ancient Egyptians utilized the observable movements of select stars to measure and track the passage of time during the night. The narrative unfolds by initially establishing the context of ancient Egyptian cosmology, emphasizing their deep reverence for the celestial realm and its perceived influence on earthly affairs. The Egyptians viewed the stars not merely as luminous points but as deities and vital components of a complex cosmic order. This reverence fueled their meticulous observations and record-keeping of celestial phenomena.
The story then delves into the mechanics of the diagonal star clocks, also known as "star tables" or "diagonal calendars." These sophisticated instruments, often inscribed on coffin lids or tomb ceilings, employed a grid system with decans – groups of stars that rose consecutively – listed across the top and rows representing sequential hours of the night. By observing which decan culminated – reached its highest point in the sky – at a specific time, one could determine the current hour. The StoryMap elucidates this process with interactive visualizations and detailed descriptions, demonstrating how the diagonal arrangement facilitated the tracking of time as different decans became prominent throughout the night. Furthermore, it highlights the evolving nature of these clocks across different periods of Egyptian history, explaining how the selection of decans and the structure of the tables adapted to account for the slow precession of the equinoxes, which causes the positions of stars to shift gradually over time.
The narrative also explores the use of transit clocks, sometimes referred to as "merkhet clocks." These relied on the observation of stars crossing the meridian, an imaginary line running north to south directly overhead. Using a merkhet, an ancient Egyptian astronomical instrument consisting of a plumb line and sighting tool, observers could precisely determine when a specific star transited the meridian, thereby marking a particular hour. The StoryMap details the practical application of this method and its integration into the broader framework of Egyptian timekeeping.
The StoryMap further elaborates on the connection between these celestial observations and the Egyptian calendar system, including the development of the civil calendar and its relationship to the rising of Sirius, the brightest star in the sky. The heliacal rising of Sirius, its first appearance on the eastern horizon just before sunrise after a period of invisibility, coincided with the inundation of the Nile, a crucial event in the agricultural cycle. This observation was not only vital for practical purposes but also imbued with religious significance, further strengthening the connection between the celestial and terrestrial realms in Egyptian thought.
Finally, the StoryMap emphasizes the remarkable precision and ingenuity of ancient Egyptian astronomy, showcasing how these star clocks provided a sophisticated means of measuring time during the night, facilitating both religious rituals and practical activities. The interactive elements and detailed explanations effectively convey the complex astronomical principles underpinning these ancient timekeeping methods, offering a glimpse into the remarkable scientific achievements of this ancient civilization.
Summary of Comments ( 2 )
https://news.ycombinator.com/item?id=42774228
HN users discussed the practicality and accuracy of Egyptian star clocks, questioning their true function. Some doubted their precision for timekeeping, suggesting they were more likely used for ritual or symbolic purposes related to the rising and setting of specific stars. Others highlighted the complexity of deciphering their meaning due to the long passage of time and shifting astronomical alignments. The role of priests in using these clocks, and their potential connection to religious ceremonies, was also a topic of interest. Several commenters appreciated the visual representation of the star clocks, but wished for more technical details and context within the ArcGIS story map itself. The limited written record from the Egyptians themselves makes definitive conclusions difficult, leaving room for speculation and further research.
The Hacker News post titled "An Astronomical View of Ancient Egyptian Star Clocks (2021)" has several comments discussing the linked article about Egyptian star clocks. Several users engaged with the content, expressing interest and offering further insights.
One commenter pointed out the cleverness of the Egyptian system, which didn't require explicit measurement of time intervals but instead focused on marking specific points in the night. This eliminated the need for precise, consistent timekeeping devices, which were technologically challenging at the time. They highlighted the practicality of this approach for religious observances and civil purposes.
Another user expanded on this idea, drawing a parallel between these star clocks and sundials. They noted that both rely on celestial movements to mark specific times or events rather than measuring durations. This user also touched on the cultural significance of these instruments, connecting them to the Egyptian understanding of cosmology and the passage of time.
Furthering the discussion on practicality, another comment mentioned the limitations of the star clocks due to weather conditions. The reliance on visible stars meant that cloudy nights rendered the clocks unusable. This observation prompted a short discussion about the challenges of timekeeping in ancient civilizations and the limitations imposed by the available technology.
One user expressed fascination with the diagonal star tables and the inherent astronomical knowledge they represent. They questioned the level of precision these ancient Egyptians possessed and wondered about the development and refinement of their astronomical observations over time.
A separate comment pointed out a detail from the linked article about the orientation of the star tables and their relation to the cardinal directions. This comment enriched the understanding of how these tables were used in practice, connecting the physical layout to the observation of star movements.
A final comment mentioned the inherent imprecision of the Egyptian system and the varying lengths of hours throughout the year. This contributed to the overall discussion of the limitations of these star clocks while acknowledging their ingenuity within the context of the available technology and knowledge.
In summary, the comments on Hacker News demonstrate a genuine appreciation for the ingenuity and cultural significance of the Egyptian star clocks. They also delve into the practical limitations and inherent imprecision of the system, reflecting a nuanced understanding of ancient Egyptian timekeeping practices.