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 ( 95 )
https://news.ycombinator.com/item?id=43737469
Hacker News users discussed the increasing problem of satellite light pollution highlighted by the image. Several commenters pointed out that the long exposures used in astrophotography exacerbate the issue, making the problem appear worse than it is to the naked eye. Others questioned the image's authenticity, suggesting the streaks could be airplanes or other phenomena. Some discussed the trade-off between the benefits of satellite internet access and the negative impact on astronomical observation. The impact of regulations and the lack of effective mitigation strategies were also mentioned, with some pessimism about finding a solution given the competing interests. A few commenters proposed technical solutions, such as improved satellite shielding or altered orbits, while others focused on the need for international cooperation and regulation of mega-constellations.
The Hacker News post titled "An image of the Australian desert illuminates satellite pollution" (linking to an article on Colossal about satellite light pollution affecting astrophotography) generated a moderate discussion with several compelling points raised in the comments.
Several commenters discussed the trade-off between the benefits of satellite internet constellations, like Starlink, and the detrimental effects on astronomical observation. One commenter highlighted the disparity between the relatively small number of people benefiting from these constellations compared to the impact on everyone's view of the night sky. Another pondered the long-term consequences of increasingly obstructed astronomical observation for scientific discovery.
The issue of regulation and mitigation was also a prominent topic. Some users suggested potential solutions, including better satellite design for reduced reflectivity, altitude adjustments, and international agreements on orbital "slots." Skepticism was expressed regarding the effectiveness and feasibility of these solutions, with one user pointing out the challenges of enforcing international regulations and the inherent limitations of mitigation efforts.
A few commenters questioned the veracity of the image presented in the Colossal article, suggesting that the sheer number of satellite trails depicted might be exaggerated or misrepresented. Others corroborated the issue, sharing anecdotal experiences of similar light pollution impacting their own astrophotography efforts.
Finally, a philosophical discussion emerged regarding humanity's impact on nature. One commenter lamented the creeping encroachment of human activity on previously untouched environments, using the satellite pollution issue as a microcosm of this larger trend. Another offered a more pragmatic perspective, arguing that the benefits of improved global internet access might outweigh the costs to a relatively niche activity like astrophotography.
While the overall sentiment leaned towards concern regarding the growing problem of satellite pollution, the discussion remained balanced, acknowledging the complexities and trade-offs involved.