Wednesday, 4 May 2011

Thoughts on the Sothic Cycle - Jean Greyling

Slightly unusual content for my blog but why not. One of my colleagues from Manchester University has some thoughts on the Sothic Cycle she wanted to share. Not having a blog herself I offered the services of mine, but these are her own thoughts. Feed back is especially welcome. Copyright Jean Greyling

THE SOTHIC CYCLE

For thousands of years the Egyptians used two calendars for record-keeping. One was an official calendar used by the civil service, and the other was a temple calendar used by the priesthood.

The official or civil calendar was a solar one with 365 days, in 12 months of 30 days each with an extra 5 days added on. It did not have the additional quarter of a day which we regulate by having a leap year every 4 years.

The religious or temple calendar was not solar but Sothic, that is a calendar governed by the star Sirius. (To the Egyptians Sirius was Sorpet or Sopdet and hence to the Greeks Sothis.) It did include the extra quarter day, and its year was 365 : 25 days.

The marker for the Sothic calendar was the heliacal – just before dawn – rising of Sirius. At one point in each cycle, just before dawn Sirius rose above the horizon in a direct line with the sun and the two calendars, solar and Sothic, synchronised.

For reasons that are clear to astronomers but not to many who try to explain them, and highly complex, to do with the different lengths of time of the earth’s rotation on its axis, its orbit round the sun, the precession of the equinoxes, and the apparent orbit of Sirius, Sothis rises above the horizon a little under four minutes earlier each day.

The result is that the two calendars drift apart by 6 hours, a quarter of a day, each year. They are thus apart by 1 day every 4 years, so 5 days after 20 years, 25 days in a century, 250 days in a millennium, and a year apart after 1460/61 years.

So the Sothic (or Siriac) calendar of the priesthood and the solar calendar of the civil bureaucracy coincide only once in every 1460 Sothic and 1461 solar years.

But they can APPEAR to be only one year apart.

* * *

Scope for confusing historians now?

All civil service, that is official and Pharaonic, records were dated by the solar calendar, and all temple ones by the Sothic calendar.

Not for nothing is the civil or solar year also known as the ‘vague’ year. (From ‘annus vagus’ or ‘wandering year’.*)

Where an event is recorded in both civil and temple records, it may appear to be only, tiresomely, a few months apart. (Ohhhh .. . . careless clerks.) BUT the records may actually be of two events hundreds of years apart.

An example in our own era – postulating that Britain’s Prince William becomes King William V – might be a reference in two sets of records, one dated by a solar calendar and the other by a Sothic one, to ‘the coronation of King William’.

William l became king of England in 1066 CE, William V is likely to be crowned nearly 1000 years – or a mere eight months of ‘calendar drift’? – later.



SOURCES:

Most coherent
Lucie Lamy, Egyptian Mysteries pub. Thames and Hudson 1981
pp 74-5

Background information
E.G. Richards, Mapping Time pub Oxford Univ. Press 1998
pp 152-6

David Ewing Duncan, The Calendar, Fourth Estate 1998
pp 22- 3

George Hart, Egyptian Gods and Goddesses, Routledge 1986
P 207


For the scope for confusion and scholarly debate arising:
David Rohl, A Test of Time, pub Arrow/Century 1995
pp 146-53, 157, 492


• Richards, op cit p 153


I’ve two questions arising –
Have I understood the Sothic Cycle correctly? and
Is my example in the last two paragraphs a valid way to interpret and apply the Sothic calendar?


There may be other questions I don’t know to ask – all comments very welcome.


Jean Greyling.
Copyright

8 comments:

Julia Thorne said...

Jean, you've understood the Sothic cycle correctly - I studied it as part of my MA, so you're taking me right back!

Julia

sschimpf said...

Jean,

“For thousands of years the Egyptians used two calendars for record-keeping. One was an official calendar used by the civil service, and the other was a temple calendar used by the priesthood.”

There’s a lot about ancient Egypt that I don’t know, and I admit I’m not very interested in anything past the end of the New Kingdom. Yet, you say “for thousands of years,” which leads me to believe your statement applies to all of ancient Egyptian history. I’ve never read about the use of two separate calendar systems and any sort of dual dating. As far as I know, dates were recorded using the civil calendar that you’ve described. Could you give me an example of a date that’s recorded using both the civil calendar and this “Sothic calendar?”

I know that the Egyptians knew that their calendar dates were out of step with nature (‘winter comes in summer and summer comes in winter’), but I don’t think they added leap days until very late in their history.

So, I don’t think there is such a thing as a “Sothic calendar.” The start of the civil calendar was supposed to happen on the helical rising of Sirius. This is simply the first day that the angular separation between the Sun and Sirius is large enough that the star can appear briefly before sunrise. (I’m not sure what “in a direct line with the sun” is supposed to mean.)

Four years later this event happens a day off, eight years later two days off, and so on. So, the civil calendar no longer corresponds to nature. As you say, after 1460/1461 years, it once again does. This period is called a Sothic period, but I’m not aware of the ancient Egyptians knowing the length of this period or using it as a basis for another calendar system.

“For reasons that are clear to astronomers but not to many who try to explain them, and highly complex, to do with the different lengths of time of the earth’s rotation on its axis, its orbit round the sun, the precession of the equinoxes, and the apparent orbit of Sirius, Sothis rises above the horizon a little under four minutes earlier each day.”

You’re overcomplicating things here, and are (I believe) confusing two different matters. All of the background stars rise about four minutes earlier each day. And the reason for this is very simple. It takes Earth 23:56:04 to rotate once on its axis. But during that time is also moves about 1/360 of the way around the Sun, or about one degree. So, it has to rotate another 4 minutes to bring the Sun back to where it was the previous day.

“The result is that the two calendars drift apart by 6 hours, a quarter of a day, each year. They are thus apart by 1 day every 4 years, so 5 days after 20 years, 25 days in a century, 250 days in a millennium, and a year apart after 1460/61 years.”

Four minutes a day for 365 days equates to about a day, as it should. Not 6 hours.

The reason for the calendar drift is not the same as the reason that objects rise four minutes earlier every day.

The reason for the calendar drift is that the length of the year is about 365.25 days, but the civil calendar only has 365 days, and the Egyptians failed to add leap days.

The reason for objects rising/transiting/setting four minutes earlier is because Earth is in motion around the Sun.

So, if the astronomical year was an integral number of days long, then there would be no Sothic cycle. But, objects would still rise four minutes earlier every day. I hope my explanation is helpful.

SynergyIsBest said...

sschimpf.
,
That is the most succinct explaination that I've read in a long time.

PeterC said...

sschimpf's details are excellent. Although the true tropic & sidereal year are closer to 365.24264 days (meaning a loss of seconds every year or about a day every 1460 years in the Julian calender, even with leap years... when all those seconds catch-up).

"The Egyptian Calendar A Work for Eternity" by A.S. von Bomhard gives a good scholarly account of the twin systems citing certain temples as latitutde points for "centering." The bibliography is loaded with excellent sources & is a fun read for calendrics enthusiasts. Afterall, the Egyptian calendar was meant to last for eternity.

Jane Akshar said...

These comments are from Jean Greyling.

Julia – Thank you! I’m so relieved, as it’s an extremely difficult subject and I felt very blinded by science while I was trying to unknot it. If you’ve read the comment that follows yours, by sschimpf, and if you’re willing, can you help to answer the questions s/he raises? I’ve listed 3, all of them my own questions too.

sschimpf – thank you for your contribution, which has raised 3 questions I can’t answer and would like to learn about too.
First, since I began looking at the Sothic Cycle I’ve understood the calendar based on it to be an ancient one, possibly older than the civil one. So Question 1 is:
What are the origins of the Sothic calendar and/or its earliest known use?

* * *

Sirius rising ‘in a direct line with the sun’ means that, at the moment the two cycles – civil and Sothic – synchronise, you would see Sirius rising directly above the sun if you were standing on the (horizontal) ground to watch them rise. You would see Sirius rise vertically above the sun. If anyone has a better explanation, please go for it!

* * *

You’re quite right that 4 minutes a day for 365 days comes to (1460 minutes – an interesting number in this context – or a little more than) one 24-hour day. The 6-hour gap each year (resulting in a leap year day in some calendars, including our present one) is, as we both say, caused by the difference between the solar year with its 365 days and the Sothic year with its 365 : 25 days. My explanation isn’t clear enough, and it’s because I’m still puzzled about the relevance of those (just under) 4 minutes earlier each day in Sirius’ time of rising above the (Egyptian) horizon. You don’t think that there is a Sothic calendar, but I do, and as I remember from trying to understand this extremely complex topic, the daily 4-minute interval has a place in explaining the solar and Sothic calendars in relation to each other. So Question 2 is:
How does the daily 4-minute interval in Sirius’ rising fit into relating the Sothic calendar to the solar one (perhaps over 1460/1461 years)?

Peter C – your comment (thank you) has helped me to leapfrog to thinking:

One way to describe the difference between the solar and Sothic calendars is: the solar calendar has a 6- HOUR gap each YEAR and the Sothic one has a 4 – minute gap each day. No wonder it takes a long cycle of years to synchronise them!
I hope this is a better and clearer explanation, and if it’s accurate and we’re getting to a reconciliation of the cycles used as calendars – thank you, sschimpf.

* * *

Question 3 is:
Are there any examples of an event recorded by both – civil/solar and temple/Sothic – calendars, and/or any examples of historians possibly confusing two such separately recorded events?
I don’t know of any, which is why I ended by guessing at an example from our own era (the coronation of Kings William 1 and V in English/British history). It would be an important and very helpful step forward to know of actual examples in ancient Egyptian history, but needs far more detailed knowledge than I have.

* * *

Peter C – thanks too for the ref. to ‘The Egyptian Calendar A Work For Eternity’ by A.S. von Bomhard. I shall happily go on wearing a hole in a seat in the library.

Stephen said...

“Sirius rising ‘in a direct line with the sun’ means that, at the moment the two cycles – civil and Sothic – synchronise, you would see Sirius rising directly above the sun if you were standing on the (horizontal) ground to watch them rise. You would see Sirius rise vertically above the sun. If anyone has a better explanation, please go for it!”

You’ve just told me that you’ve never actually gone outside to watch the sky and are unfamiliar with where Sirius is!

The heliacal rising takes place in July, when the Sun is near the northern solstice, so its declination is a bit lower than the maximum of about 24 degrees. Sirius has a declination of about -17 degrees. That alone should tell you that what you describe above can’t happen.

If I’m watching during the middle of the New Kingdom, from Luxor, then at or near its heliacal rising Sirius rises at azimuth 110 degrees. The Sun rises at azimuth 63 degrees almost an hour later. So, Sirius rises about 37 degrees to the south of the Sun.

These numbers change a bit for different observing locations, and if you move the clock forward or backward by a thousand years, but you won’t find Sirius rise “vertically above the Sun.” Not even close.

If you’re a Windows user, feel free to download a copy of my CyberSky software from www.cybersky.com and take a look at the situation yourself. I’m sure there are similar programs for the Mac if that’s what you use.

I honestly think you’re struggling with something that’s really pretty basic, and you just need to either take an introductory astronomy course or spend a few hours with any decent planetarium program to understand where things are in the sky and how they move over time.

“Are there any examples of an event recorded by both – civil/solar and temple/Sothic – calendars, and/or any examples of historians possibly confusing two such separately recorded events? ... I don’t know of any, ...”

Okay. Let me get this straight...

You wrote “For thousands of years the Egyptians used two calendars for record-keeping. One was an official calendar used by the civil service, and the other was a temple calendar used by the priesthood. “

But now you write that you don’t know of any example of the dating of an event with both the normal Egyptian calendar and the “Sothic calendar” that you believe existed.

So I just have to ask: what reason do you have to believe in the existence of a Sothic calendar if you have no example of any use of such a calendar?

Jane Akshar said...

Stephen – Thank you for your comment.

Yes, I’m an ignoramus about astronomy, with no background in science and a Maths career that peaked at O-grade. I travelled overland in Africa, including a full cycle of the moon in the Western Sahara, and spent most nights in the open (not in a tent) for 7 months. Believe me, I’ve been outside and watched the sky (on other occasions too), and I’ve looked at star maps, but not as an astronomer.

Do you know the jigsaw puzzle ‘The Celestial Planisphere’? I completed that and was about to frame it as my preferred sky-map, when it was accidentally broken up.

I’ve come to the Sothic Cycle as an amateur, hobby-interest student of ‘far’ history – the area where myth, legend, and recorded history meet, the factual discovery of the till-then legendary city of Troy being an example – and came to wish for a ‘Rosetta Stone’, not of scripts, but of ways to measure time/chronologies. Ancient Egypt is or could be a good example, with its civil calendar, (the possibility of) a temple/Sothic calendar, and the Great Year with its ‘months’ or epochs.

Why do I think there is a Sothic calendar? I refer you to L. Lamy’s ‘Egyptian Mysteries’ p 74, right-hand column.

Peter C suggested I look at A S von Bomhard’s ‘The Egyptian Calendar A Work For Eternity’, and the idea of a ‘gliding calendar’ is a great help to me. It’s letting me understand astronomical cycles and their possible uses as calendars in relation to each other. If you don’t know this work, I strongly recommend it too.

I note that neither you nor sschimpf have commented on my hypothetical example of ‘the coronation of King William’. Clearly it’s an example I’ve ‘dreamt up’, but I think it demonstrates – doesn’t it? – the principle of how a civil/solar calendar and a temple/Sothic one could work alongside each other (and be open to our misunderstanding).

* * *

It’s been very generous of Jane to invite me onto her blog and to host our discussion. I’m sorry to draw a line under it at this point, but I know Jane is busy and getting busier and I feel I’d be imposing on her to go on any longer. So I’ll ‘close down’ now, with thanks again to everyone who’s commented on my thoughts on the Sothic Cycle.

JEAN GREYLING.

Jane Akshar said...

I want to thank Jean for being brave enough to publish her thoughts and for everyone that commented on the discussion.