5 ms·

An astronomical view of Ancient Egyptian star clocks (2021)

throw0101d 2y ago
Doesn't mention north stars at all sadly. While we all (should) know that the Earth rotates on its axis, not as many people know that the axis is 'wobbly', kind of like a children's top as it slows down a bit. So a line that goes through the North and South Poles points differently over time: currently it points roughly to Polaris, but go back a while—e.g., Ancient Egypt—and it pointed to Thuban (and other starts between then and now): * https://en.wikipedia.org/wiki/Pole_star https://en.wikipedia.org/wiki/Pole_star * https://en.wikipedia.org/wiki/Polaris https://en.wikipedia.org/wiki/Polaris * https://en.wikipedia.org/wiki/Thuban https://en.wikipedia.org/wiki/Thuban See also two related stars for the Egyptians: * https://en.wikipedia.org/wiki/The_Indestructibles https://en.wikipedia.org/wiki/The_Indestructibles The current idea is that they used those star(s) to align the pyramids: * https://www.astronomy.com/science/are-the-egyptian-pyramids-aligned-with-the-stars/ https://www.astronomy.com/science/are-the-egyptian-pyramids-... * https://earthsky.org/brightest-stars/thuban-past-north-star/ https://earthsky.org/brightest-stars/thuban-past-north-star/ * https://www.science.org/content/article/stars-date-egyptian-pyramids https://www.science.org/content/article/stars-date-egyptian-... If anyone is traveling/visiting the Western US, and can drop by the Hoover Dam, a similar astronomical design element is present: > On the western flank of the Hoover Dam stands a little-understood monument, commissioned by the US Bureau of Reclamation when construction of the dam began in 01931. The most noticeable parts of this corner of the dam, now known as Monument Plaza, are the massive winged bronze sculptures and central flagpole which are often photographed by visitors. The most amazing feature of this plaza, however, is under their feet as they take those pictures. > The plaza’s terrazzo floor is actually a celestial map that marks the time of the dam’s creation based on the 25,772-year axial precession of the earth. * https://medium.com/the-long-now-foundation/the-26-000-year-astronomical-monument-hidden-in-plain-sight-9ec13c9d29b5 https://medium.com/the-long-now-foundation/the-26-000-year-a...
- antiatheist 2y ago
  Called The Precession of the Equinoxes or Axial Precesion, the ancient societies including Egypt were also aware of this, and even bronze age cultures may have been aware (golden hats, megalithic calendars) or atleast of the related 19 year lunisolar cycle. iirc Christmas and other mythological holidays are related to the "birth" and "death" of the north star movements, along with the sun and venus.
  - thaumasiotes 2y ago
    Christmas is on the calendar day traditionally called the winter solstice; it seems unnecessary to look for another explanation than that already major event. (The Romans at the relevant time were aware that the solstice didn't actually occur on the 25th, but the 25th was the traditional day of the solstice.)
    - adrian_b 2y ago
      Actually the solstice occurred on the 25th during the years immediately after the calendar reform of Julius Caesar. This is when the 25th has become the traditional date for what has later been reinterpreted as Christmas. Before the Julian calendar, the solstices occurred on random dates of the Roman calendar, because the duration of the Roman year differed very much from the duration of the solar year. Today it occurs around the 22th as a consequence of the Gregorian calendar reform, which has not restored the solstices and equinoxes from the beginning of the Christian era, but those from around 325 AD, when the Christian algorithm for computing the date of Easter has been established (First Council of Nicaea). Between Julius Caesar and the 4th century AD, 3 days of offset in the solstices and equinoxes had accumulated, due to the difference in duration between the Julian year and the tropical year.
      - thaumasiotes 2y ago
        > Actually the solstice occurred on the 25th during the years immediately after the calendar reform of Julius Caesar. So? I took my information from https://kiwihellenist.blogspot.com/2015/12/christmas-and-its-supposed-pagan-links.html https://kiwihellenist.blogspot.com/2015/12/christmas-and-its... : > Around the time of Jesus' birth, the solstice was on 23 December; by the time of the Chronography of 354, it was 20 December. Are you saying the right date to determine the solstice for purposes of assigning Christmas was 40 years before Christ was notionally born? Also, why are you saying that the solstice fell on the 22nd in 325 when it actually fell on the 20th? In 325, the solstice hadn't occurred on the 22nd for at least 90 years. Also, your original point wasn't even true: > Digression #2: why do Roman writers report the date of the solstice as 25 December? The textual parallels between Columella and Pliny, and the fact that the date was already wrong by their time, suggest they are both based on an older source. A few pages earlier Pliny discusses three treatises by Sosigenes [] (Nat. hist. 18.212). Sosigenes can’t be the ultimate origin of the date either: in his time, in 46 BCE, the solstice had already drifted to 23 December. > The last time the solstice actually fell on 25 December, using the retrojected Julian calendar, was in [214] BCE
throw0101d 2y ago
A researcher gave a presentation on this topic a few years ago, "It's Sirius O'Clock: Astronomical Timekeeping in Ancient Egypt": > Ever wondered how the Ancient Egyptians kept time? Well, Dr. Sarah Symons from McMaster University wondered about this, too. With the help of some of her colleagues, she participated in a research project to find out how they managed time. On April 10, 2019, she presented some of her findings at the Royal Astronomical Society of Canada - Toronto Centre's Speaker's Night. The meeting was held at the Ontario Science Centre in Toronto Canada. * https://www.youtube.com/watch?v=Ak07dI-TALU https://www.youtube.com/watch?v=Ak07dI-TALU * https://experts.mcmaster.ca/display/symonss https://experts.mcmaster.ca/display/symonss
Theodores 2y ago
Very impressive web page, particularly for 2021. I like it how 'slides' are presented in the midst of text. Is this an ArcGis thing?
- xtiansimon 2y ago
  It’s also impressive on mobile.
dr_dshiv 2y ago
More than a thousand years after these Middle Kingdom coffin lids, highly engineered mechanical star trackers (astrolabes) were used to calculate the time at night. Here’s a letter accompanying the gift of a gold and silver astrolabe from the Lybian philosopher Synesius to a Byzantine general. Interestingly, it shows that Hypatia of Alexandria contributed to the design of Synesius’ Astrolabe. It further indicates that Astrolabes could be used as “night clocks” and as instruments of philosophical investigation. https://www.livius.org/sources/content/synesius/synesius-on-an-astrolabe/synesius-on-an-astrolabe-3/ https://www.livius.org/sources/content/synesius/synesius-on-... “I am therefore offering you a gift most befitting for me to give, and for you to receive. It is a work of my own devising, including all that she, my most reverend teacher [Hypatia], helped to contribute, and it was executed by the best hand to be found in our country in the art of the silversmiths” The letter also discusses how much geometry and astronomy had progressed since the time of Ptolemy. Hypatia’s father, Theon of Alexandria, had recently published “Euclid’s Elements of Geometry,” the most successful and influential geometry textbook of all time. I’ll note that this work was almost certainly produced with the help of his mathematical genius daughter, even if she wasn’t formally credited. But nice to see Synesius credit her so directly here, in the production of this mechanical star computer (as I believe an astrolabe has right to be called). And, while he did not credit the Egyptians, he credits the beginnings of the Greek philosophical knowledge of the stars to Pythagoras (who is claimed by Iamblichus to have become an Egyptian priest).

Doesn't mention north stars at all sadly. While we all (should) know that the Earth rotates on its axis, not as many people know that the axis is 'wobbly', kind of like a children's top as it slows down a bit. So a line that goes through the North and South Poles points differently over time: currently it points roughly to Polaris, but go back a while—e.g., Ancient Egypt—and it pointed to Thuban (and other starts between then and now): * https://en.wikipedia.org/wiki/Pole_star https://en.wikipedia.org/wiki/Pole_star * https://en.wikipedia.org/wiki/Polaris https://en.wikipedia.org/wiki/Polaris * https://en.wikipedia.org/wiki/Thuban https://en.wikipedia.org/wiki/Thuban See also two related stars for the Egyptians: * https://en.wikipedia.org/wiki/The_Indestructibles https://en.wikipedia.org/wiki/The_Indestructibles The current idea is that they used those star(s) to align the pyramids: * https://www.astronomy.com/science/are-the-egyptian-pyramids-aligned-with-the-stars/ https://www.astronomy.com/science/are-the-egyptian-pyramids-... * https://earthsky.org/brightest-stars/thuban-past-north-star/ https://earthsky.org/brightest-stars/thuban-past-north-star/ * https://www.science.org/content/article/stars-date-egyptian-pyramids https://www.science.org/content/article/stars-date-egyptian-... If anyone is traveling/visiting the Western US, and can drop by the Hoover Dam, a similar astronomical design element is present: > On the western flank of the Hoover Dam stands a little-understood monument, commissioned by the US Bureau of Reclamation when construction of the dam began in 01931. The most noticeable parts of this corner of the dam, now known as Monument Plaza, are the massive winged bronze sculptures and central flagpole which are often photographed by visitors. The most amazing feature of this plaza, however, is under their feet as they take those pictures. > The plaza’s terrazzo floor is actually a celestial map that marks the time of the dam’s creation based on the 25,772-year axial precession of the earth. * https://medium.com/the-long-now-foundation/the-26-000-year-astronomical-monument-hidden-in-plain-sight-9ec13c9d29b5 https://medium.com/the-long-now-foundation/the-26-000-year-a...

antiatheist 2y ago
Called The Precession of the Equinoxes or Axial Precesion, the ancient societies including Egypt were also aware of this, and even bronze age cultures may have been aware (golden hats, megalithic calendars) or atleast of the related 19 year lunisolar cycle. iirc Christmas and other mythological holidays are related to the "birth" and "death" of the north star movements, along with the sun and venus.
- thaumasiotes 2y ago
  Christmas is on the calendar day traditionally called the winter solstice; it seems unnecessary to look for another explanation than that already major event. (The Romans at the relevant time were aware that the solstice didn't actually occur on the 25th, but the 25th was the traditional day of the solstice.)
  - adrian_b 2y ago
    Actually the solstice occurred on the 25th during the years immediately after the calendar reform of Julius Caesar. This is when the 25th has become the traditional date for what has later been reinterpreted as Christmas. Before the Julian calendar, the solstices occurred on random dates of the Roman calendar, because the duration of the Roman year differed very much from the duration of the solar year. Today it occurs around the 22th as a consequence of the Gregorian calendar reform, which has not restored the solstices and equinoxes from the beginning of the Christian era, but those from around 325 AD, when the Christian algorithm for computing the date of Easter has been established (First Council of Nicaea). Between Julius Caesar and the 4th century AD, 3 days of offset in the solstices and equinoxes had accumulated, due to the difference in duration between the Julian year and the tropical year.
    - thaumasiotes 2y ago
      > Actually the solstice occurred on the 25th during the years immediately after the calendar reform of Julius Caesar. So? I took my information from https://kiwihellenist.blogspot.com/2015/12/christmas-and-its-supposed-pagan-links.html https://kiwihellenist.blogspot.com/2015/12/christmas-and-its... : > Around the time of Jesus' birth, the solstice was on 23 December; by the time of the Chronography of 354, it was 20 December. Are you saying the right date to determine the solstice for purposes of assigning Christmas was 40 years before Christ was notionally born? Also, why are you saying that the solstice fell on the 22nd in 325 when it actually fell on the 20th? In 325, the solstice hadn't occurred on the 22nd for at least 90 years. Also, your original point wasn't even true: > Digression #2: why do Roman writers report the date of the solstice as 25 December? The textual parallels between Columella and Pliny, and the fact that the date was already wrong by their time, suggest they are both based on an older source. A few pages earlier Pliny discusses three treatises by Sosigenes [] (Nat. hist. 18.212). Sosigenes can’t be the ultimate origin of the date either: in his time, in 46 BCE, the solstice had already drifted to 23 December. > The last time the solstice actually fell on 25 December, using the retrojected Julian calendar, was in [214] BCE

throw0101d 2y ago

A researcher gave a presentation on this topic a few years ago, "It's Sirius O'Clock: Astronomical Timekeeping in Ancient Egypt": > Ever wondered how the Ancient Egyptians kept time? Well, Dr. Sarah Symons from McMaster University wondered about this, too. With the help of some of her colleagues, she participated in a research project to find out how they managed time. On April 10, 2019, she presented some of her findings at the Royal Astronomical Society of Canada - Toronto Centre's Speaker's Night. The meeting was held at the Ontario Science Centre in Toronto Canada. * https://www.youtube.com/watch?v=Ak07dI-TALU https://www.youtube.com/watch?v=Ak07dI-TALU * https://experts.mcmaster.ca/display/symonss https://experts.mcmaster.ca/display/symonss

Theodores 2y ago

Very impressive web page, particularly for 2021. I like it how 'slides' are presented in the midst of text. Is this an ArcGis thing?

xtiansimon 2y ago
It’s also impressive on mobile.

dr_dshiv 2y ago

More than a thousand years after these Middle Kingdom coffin lids, highly engineered mechanical star trackers (astrolabes) were used to calculate the time at night. Here’s a letter accompanying the gift of a gold and silver astrolabe from the Lybian philosopher Synesius to a Byzantine general. Interestingly, it shows that Hypatia of Alexandria contributed to the design of Synesius’ Astrolabe. It further indicates that Astrolabes could be used as “night clocks” and as instruments of philosophical investigation. https://www.livius.org/sources/content/synesius/synesius-on-an-astrolabe/synesius-on-an-astrolabe-3/ https://www.livius.org/sources/content/synesius/synesius-on-... “I am therefore offering you a gift most befitting for me to give, and for you to receive. It is a work of my own devising, including all that she, my most reverend teacher [Hypatia], helped to contribute, and it was executed by the best hand to be found in our country in the art of the silversmiths” The letter also discusses how much geometry and astronomy had progressed since the time of Ptolemy. Hypatia’s father, Theon of Alexandria, had recently published “Euclid’s Elements of Geometry,” the most successful and influential geometry textbook of all time. I’ll note that this work was almost certainly produced with the help of his mathematical genius daughter, even if she wasn’t formally credited. But nice to see Synesius credit her so directly here, in the production of this mechanical star computer (as I believe an astrolabe has right to be called). And, while he did not credit the Egyptians, he credits the beginnings of the Greek philosophical knowledge of the stars to Pythagoras (who is claimed by Iamblichus to have become an Egyptian priest).