How did the Egyptians calculate the first hour?

Part of the astronomical ceiling at the Dendera temple, Egypt. Photo: Kairoinfo4u

The relationship between humans and time is very old and understanding the origins of many units of time is a great challenge for experts. Some units originate from astronomical phenomena that are quite easy to explain and can be observed independently in many different cultures around the world . For example, measuring the length of a day or a year can use the relative motion of the Sun with respect to the Earth, while measuring months depends on the phase of the Moon.

However, some units of time have no obvious connection to any astronomical phenomenon, such as weeks and hours, according to Robert Cockcroft, associate professor of astrophysics, and Sarah Symons, professor of interdisciplinary science at McMaster University. One of the oldest scripts, Egyptian hieroglyphics, provides information about the origin of hours. It originated in North Africa and the Middle East, was adopted in Europe, and then spread around the world, IFL Science reported on July 8.

Time in Ancient Egypt

The Pyramid Texts, written before 2400 BC, are the earliest written records of ancient Egypt. The text contains the word wnwt (pronounced roughly “wenut”), and the hieroglyph associated with the word is a star. Based on this, experts have deduced that wnwt is related to night.

wnwt today translates as “hour,” and to learn about the term, one must first travel to the city of Asyut around 2000 BC. There, the inside of rectangular wooden coffin lids was sometimes decorated with astronomical tables.

The table contains columns representing the ten-day periods of a year. The ancient Egyptian calendar had 12 months, each month had three weeks and each week had ten days, with a series of five festival days at the end of each year. In each column, the names of 12 stars were listed, forming 12 rows. The entire table represented changes in the sky over the course of a year, similar to a modern star map.

These 12 stars were the earliest systematic division of the night into 12 periods, each corresponding to a star. But during this period, the word wnwt did not appear with the sarcophagus tables. It was not until around 1210 BC, during the New Kingdom of Egypt (16th - 11th centuries BC), that the connection between the number of rows and the word wnwt became clear. For example, in the Osireion temple at Abydos there is an astronomical table on a sarcophagus, in which the 12 rows are labeled with the word wnwt.

During the New Kingdom of Egypt, there were 12 wnwt nights and 12 wnwt days, both of which were used to measure time. So “wnwt” had almost the same meaning as modern “hour”, except for two things.

First, although there are 12 hours of daylight and 12 hours of darkness, they are still expressed separately rather than being combined into a 24-hour day. The hours of daylight are measured based on the shadows cast by the Sun, while the hours of darkness are mainly based on the stars. This can only be done when the Sun and stars are in view, so there are two times near dawn and dusk that do not contain any hours.

Second, wnwt differs from present time in length. The length of wnwt changes during the year, with nighttime hours near the winter solstice getting longer and daylight hours near the summer solstice getting longer.

The Osireion temple at Abydos provides a wealth of astronomical information. Photo: Hannibal Joost

The stars measure time

To answer the question of where the number 12 or 24 comes from, it is necessary to understand why the Egyptians chose 12 stars for each period of 10 days. This choice is also the true origin of the hour.

The ancient Egyptians used Sirius (or Sirius, the brightest star in the night sky) as a model and selected other stars based on how similar they behaved to Sirius. The key factor in their selection seems to have been that they disappeared for 70 days a year, just like Sirius, though they were not as bright. Every 10 days, one Sirius-like star disappeared and another reappeared.

Depending on the time of year, 10 to 14 such stars become visible each night. If the 10-day periods of the year are recorded, experts will get a table very similar to the astronomical table in the coffin.

It is therefore likely that the choice of 12 as the number of hours of night (which eventually led to a total of 24 hours a day) involved the choice of a 10-day week. Thus, human hours today originate from a convergence of decisions made more than 4,000 years ago.

Source VNE

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