This is the second part of Measuring time : What, Why and How? In this part we will talk about 24 hours? Who divided the day in 24 hours? why 24? and some other stuff.
In the last video, we talked about the most basic observation of dynamism of time that is day. We saw the various variations in different methods we have used throughout the history and found sun as our best source for measuring day.
Now we may wonder who divided the day in 24 hours? The answer is Egyptians.
Egyptians had shadow clocks i.e. sundials in which they marked daylight into twelve parts. These 12 parts were further divided as 1-10-1 hours where the single ones represent first and last hour where the sundial was not so effective.
Similarly the night was also divided into 12 hours (named as wnwt).
The system used for night sky was a complex system with usage of stars. There
were 36 constellations (now called as decans). Each one for 10 days and some
other sets for the leftover days of the year (we will talk about these in the
video for years). Since this system included such complexity, there were tables
made to determine the time using stars and how do we know that? Because the
tables were found on the walls of Egyptian burials (specifically inside the
lids of coffins) so that the dead could also tell the time in their after-life.
Heading towards the next question : Why 24? Actually it was 12. And why 12? No one knows. Maybe because of 12 finger joints. Nah! this seems lame. But there are some not so lame and actually believable theories on number 12 as it was used also by the Chinese in timekeeping as they used 12 “double hours” and we know these civilizations had a pretty good knowledge of mathematics. 12 is LCM of 1,2,3 and 4 the first four digits. So 12 was a number which can be group in pairs, in triplets or in quadruples.
One more analogy with geometry that 12 can be represented by 4 triangles or 3 squares and the information could have been stored using a side as a representation of an hour.
The Egyptian hours were unequal. The day time hour was longer than the
night hours in summer and vice versa in winter. This fact also led to
observation of equinoxes and solstices. If you want me to cover the science as
well as religious importance of equinox and solstice do let me know in the
comment box.
This system was adopted by Romans and Greeks with a change in night system which included four vigils of three hours. Use of any basic instrument would have revealed the difference and the instrument used is believed to be water clocks.
The astronomers divided the day in 24 equal hours
as it was on equinoxes. And from then both system were used side by side for a good amount of time but the equal system of hours very slowly became the norm.
The start of day also varied a lot with options from sunrise, noon, sunset and midnight. We will not go in the details of it as I have taken some good minutes from your precious time. I’ll definitely try to return them in my next video on minutes and seconds.
Sources and Attribution notes :
The History Of Time : A Very Short Introduction by OXFORD PUBLICATIONS (https://www.amazon.in/History-Time-Short-Introduction-Introductions/dp/0192804995) Wikipedia : Time (https://en.wikipedia.org/wiki/Time), Hour (https://en.wikipedia.org/wiki/Hour)
Egyptian Sundial : https://commons.wikimedia.org/wiki/File:Ancient-egyptian-sundial.jpg By SenemmTSR - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11318720 By Einsamer Schütze - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3936351
In the last video, we talked about the most basic observation of dynamism of time that is day. We saw the various variations in different methods we have used throughout the history and found sun as our best source for measuring day.
 |
| piece of a sundial |
Now we may wonder who divided the day in 24 hours? The answer is Egyptians.
Egyptians had shadow clocks i.e. sundials in which they marked daylight into twelve parts. These 12 parts were further divided as 1-10-1 hours where the single ones represent first and last hour where the sundial was not so effective.
Similarly the night was also divided into 12 hours (named as wnwt).
The system used for night sky was a complex system with usage of stars. There
were 36 constellations (now called as decans). Each one for 10 days and some
other sets for the leftover days of the year (we will talk about these in the
video for years). Since this system included such complexity, there were tables
made to determine the time using stars and how do we know that? Because the
tables were found on the walls of Egyptian burials (specifically inside the
lids of coffins) so that the dead could also tell the time in their after-life.Heading towards the next question : Why 24? Actually it was 12. And why 12? No one knows. Maybe because of 12 finger joints. Nah! this seems lame. But there are some not so lame and actually believable theories on number 12 as it was used also by the Chinese in timekeeping as they used 12 “double hours” and we know these civilizations had a pretty good knowledge of mathematics. 12 is LCM of 1,2,3 and 4 the first four digits. So 12 was a number which can be group in pairs, in triplets or in quadruples.
One more analogy with geometry that 12 can be represented by 4 triangles or 3 squares and the information could have been stored using a side as a representation of an hour.
But this isn’t it about the
HOURS.
This system was adopted by Romans and Greeks with a change in night system which included four vigils of three hours. Use of any basic instrument would have revealed the difference and the instrument used is believed to be water clocks.
The start of day also varied a lot with options from sunrise, noon, sunset and midnight. We will not go in the details of it as I have taken some good minutes from your precious time. I’ll definitely try to return them in my next video on minutes and seconds.
Sources and Attribution notes :
The History Of Time : A Very Short Introduction by OXFORD PUBLICATIONS (https://www.amazon.in/History-Time-Short-Introduction-Introductions/dp/0192804995) Wikipedia : Time (https://en.wikipedia.org/wiki/Time), Hour (https://en.wikipedia.org/wiki/Hour)
Egyptian Sundial : https://commons.wikimedia.org/wiki/File:Ancient-egyptian-sundial.jpg By SenemmTSR - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11318720 By Einsamer Schütze - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3936351
Post a Comment