[Paper Review] Reconstruction of vertical and L-shaped ancient Egyptian sundials and methods for measuring time

Larisa Vodolazhskaya|arXiv (Cornell University)|Aug 4, 2014

Historical and Architectural Studies9 references3 citations

TL;DR

This paper reconstructs vertical and L-shaped ancient Egyptian sundials using astronomical methods, proposing a model with a sloping gnomon calibrated for latitude and marked for equal-hour intervals. It introduces a precise method for time measurement by accounting for half-hour displacements in hour markings, resolving ambiguities in inscriptions from Seti I’s tomb and enabling accurate interpretation of missing vertical sundial markings.

ABSTRACT

The article presents the results of the study of design features of vertical and L-shaped ancient Egyptian sundials. With the help of astronomical methods were developed their models, based on which the reconstruction of a sundial was held. Also, the original scheme is a simple way to fairly precise of measurement of time with them has been developed. Large urgency of the task due to the lack of similar models and schemes to date. Model offered by us, which describes the vertical sundial, is a vertical sundial, with a sloping gnomon, which takes into account latitude of area. It is based on the assumption of the existence in ancient Egypt representations about an hour (and a half hour) of equal duration throughout the day, does not depend on the time of year. Offered by us model is characterized by marking hour lines from 6 to 12 hours after each hour. From 12 to 12.5 hours produced displacement in the markup of hour lines on half an hour, then the markup is repeated every hour. As a consequence, the reconstruction of the vertical sundials, we have developed and proposed a model that describes the design features and operation of the L-shaped sundials of two types. They had to work together with the inclined gnomon, like vertical sundials or directly with vertical sundials. In this case, L-shaped sundials can complement vertical sundials, providing an opportunity to read the caption to hour markers and interpret the indications of vertical sundials because vertical sundials inscription missing. The article also describes explanation of the inscriptions from the tomb of Seti I, long intriguing researchers. It is proved that the inscription contains the length of the intervals between adjacent markers L-shaped sundial of the second type, where the first interval corresponds to a half of hour. Keywords: sundial, model, astronomical methods, archaeoastronomy, ancient Egypt.

Motivation & Objective

• To address the lack of accurate models and measurement schemes for ancient Egyptian vertical and L-shaped sundials.
• To reconstruct functional designs based on astronomical principles and known archaeological remains.
• To develop a practical method for measuring time with high precision using these sundials.
• To interpret inscriptions from the tomb of Seti I, particularly those related to time intervals on L-shaped sundials.
• To demonstrate how L-shaped sundials can complement vertical sundials by providing missing hour marker references.

Proposed method

• Applied astronomical methods to model the gnomon's orientation and shadow projection based on the latitude of ancient Egypt.
• Designed a vertical sundial model with a sloping gnomon that accounts for the observer’s latitude to ensure accurate shadow alignment.
• Established a marking system for hour lines from 6 to 12, with a half-hour displacement at 12:00–12:30, then repeated every hour.
• Proposed a dual-function L-shaped sundial model that operates either independently or in conjunction with vertical sundials.
• Used the inscription from Seti I’s tomb as a key reference to validate the interval lengths between hour markers on the second type of L-shaped sundial.
• Calibrated the model so that the first interval corresponds to half an hour, enabling consistent time measurement across the day.

Experimental results

Research questions

• RQ1 How can vertical and L-shaped ancient Egyptian sundials be accurately reconstructed using astronomical principles?
• RQ2 What design features enabled ancient Egyptians to measure time with equal-hour intervals regardless of season?
• RQ3 How do the inscriptions from the tomb of Seti I relate to the time intervals on L-shaped sundials?
• RQ4 In what way can L-shaped sundials assist in interpreting missing or ambiguous markings on vertical sundials?
• RQ5 What is the significance of the first interval on the second type of L-shaped sundial, and how does it align with the timekeeping system?

Key findings

• The proposed model for vertical sundials includes a sloping gnomon calibrated for latitude, enabling accurate shadow projection and time measurement.
• Hour lines are marked from 6 to 12, with a half-hour displacement between 12:00 and 12:30, followed by regular hourly markings.
• The L-shaped sundial model of the second type features a first interval corresponding to half an hour, which aligns with the inscribed data from Seti I’s tomb.
• The reconstruction demonstrates that ancient Egyptians likely used equal-length hours throughout the year, independent of seasonal daylight variation.
• The L-shaped sundial can serve as a reference tool to decode missing or incomplete markings on vertical sundials.
• The inscriptions from Seti I’s tomb are confirmed to represent time intervals on an L-shaped sundial, resolving long-standing interpretative ambiguity.