Getting Sirius About Time
The ancients didn't use the stars much for time keeping because it's much more complicated than using
the sun or moon. Planets wander around, comets zip around. And, there are so many stars!
But, all those stars must mean something, so ...
- Pick a bright star
(one you can see). To resonate with the Ancient Mysteries Of The Pyramids, use
alpha Canis Majoris, the brightest star in the sky. The Old Kingdom Egyptians used it to
predict when the Nile would flood (and probably to play Senet too).
- Then, learn the astronomical coordinate system so you can find Sirius,
(For finding stars and planets, nothing beats an iPad - there's an app that uses the built-in
hardware to show the sky where you point it, anywhere in the world.)
- get familiar with sidereal time
- the crab-like rotation of the earth relative to the stars, and how to find it
from the date or
on line, and
- find your latitude and longitude, from a map or
At this point, you can calculate a current star time-of-day. But, since the stars
are forever, you should extend your calculation for more than a few mere centuries
from the present. So, you really must
And, when you want to see the Sirius year as the pyramids saw it, you will also have to
- read a bit about calendars, particularly the roots of our present one.
- learn about the non-spherical shape of the earth, and
- learn basic spherical trigonometry (cosine and sine rules) so you can
- calculate the precession
of the earth's rotation about the pole of the ecliptic,
- calculate the proper motion of Sirius, and
- check out the
Project, to understand how much the earth's surface flows around. (The continental
plate on which the pyramids sit is not perceptibly rotating, but your plate may be.)
Then, you have to choose your data. Here is where I got mine:
- station longitude and latitude: 1:50000 topographical map (Geological Survey of Canada)
- Sirius coordinates:
- Sirius proper motion:
Hipparcos Catalogue Vol.1 Table 3.6.1
- precession eccentricity: Astronomie populaire Flammarion (1960)
- precession mean period: a value attributed to "Stockwell" in a reference I've misplaced
- sidereal time coefficients:
Explanatory Supplement to the Astronomical Almanac p.50
Based on this data, it appears that the current Sirius year began approximately at 0540 UT
25 August 9967 BC Gregorian, and will have a length of about 9 327 011.52 Sirius days.
Further work is planned to refine these values and to organize this year into suitable subdivisions.