Astronomy web page  


Update April 14, 2016 The Lascaux Sky Chart

 
Original posting November 27, 2012



NOTICE
April 28, 2016
The conclusions on this page may include minor errors that have been corrected with the most recent Cartes du Ciel software update.  The web page The Lascaux Sky Chart includes these changes. These changes are NOT yet reflected in the web pages Astronomy.html, Lascaux.html, and ZodiacClock.html. In particular, the animations need to be corrected. This notice will be removed from the updated pages as the corrections are completed.



In Celebration of Psalm Nineteen:
God's handiwork in Creation

THE ZODIAC CLOCK*
by
David C. Bossard
19thpsalm.org

"Let them be for signs and for seasons,
and for days and for years"
Genesis 1:14

The signs of the zodiac have marked the seasons long before the dawn of recorded history, although the specific identification of the signs may have changed from time to time, and the division of the year into twelve signs marking twelve months is of uncertain origin. The Sun passes through the zodiac signs on its annual course, and is said to be in the "house" of a particular constellation while it passes through.

The zodiac signs lay in the distant background of the "fixed" stars along the ecliptic, which is the path of the Sun in the night sky. The ecliptic traces out the plane formed by Earth's orbit around the Sun in this background of fixed stars. The ecliptic plane is quite stable over periods of many thousands of years -- over the period of human existence -- although in the very long timeframe—a period of about 110,000 years—it does precess against the background of the fixed stars. For our purposes, though, it is fixed.

In their intrinsic sense, the zodiac signs of the seasons have no mystical or astrological meaning: that came much later.  They are, as Genesis states, "for seasons." Four seasons have both physical and practical meaning: the beginning of Spring, Summer, Fall and Winter have a direct impact on humans, because they point to major changes in how a person must prepare for and survive the near future. These four signs of seasonal change mark, in order: the Spring Equinox, the Summer Solstice, the Fall or Autumnal Equinox, and the Winter Solstice and occur around March 21, June 21, September 21 and December 21. At the equinoxes the day and night are of roughly equal length. The day is longest near the Summer Solstice and shortest near the Winter Solstice, the specific dates and durations dependent on the observer's latitude.

The point of the zodiac clock is that over the span of hundreds and thousands of years, the zodiac signs slowly move through the months and seasons. The zodiac clock records this movement, called precession of the equinoxes.

NOTICE: The Zodiac Clock presented here is based on the sky chart program Cartes du Ciel Version 3.6, and the Hipparcos star catalog.



Animations on this page

Zodiac Clock Cycle (Polar + perihelion precession) -- This animation shows the sky charts at the Autumnal Equinox (Sept. 21) at the transition between Zodiac Signs over a complete cycle (27,500 BC to 11,000 AD). (MP4, 1.4 Mb, 45 s).

Zodiac Clocks (Polar + perihelion precession) -- This animation shows the zodiac clocks at 1000 year intervals over the above zodiac precession cycle cycle: 11,000 AD to 27,000 BC (MP4, 2.2 Mb, 2m 6s -- 900x900 pixels; 5 Mb gif animation here). 
Zodiac Clock (large): 4,000 AD to 15,300 BC (MP4, 1.9 Mb; 1m 8s - 2400x2400 pixels).

(Erroneous) Traditional Zodiac Clock (Polar precession only) -- The above animations are consistent with the Cartes du Ciel sky chart. Many traditional calculations of the zodiac positions erroneously consider only Polar precession, shown here between 4,000 AD and 15,300 BC (MP4, 1.3 Mb, 1m 15s; 2.1 Mb gif animation here). This animation shows the results of the erroneous calculation. See also Figure 4.


Note: Click on the images in this page for an expanded view.

The Ecliptic and Signs of the Zodiac. The Ecliptic is the path that the Sun appears to travel in its annual journey through the fixed star background as viewed from Earth. Twelve constellations that fall along the ecliptic form the signs of the Zodiac and mark of the months of the year. The Sun rises and sets in the "House" of each constellation in turn as the year progresses month by month; that is, this constellation is visible on the horizon in the direction of the Sun just before dawn and/or just after sunset. The constellations mark the months, and the constellations at the equinoxes and solstices mark the beginnings of each season.

Over the span of human existence, the ecliptic has hardly changed, so the 12 constellations that form the Zodiac are valid for the entire span, although some other constellations that also lay along the ecliptic have sometimes been substituted for the 12 that are named here. For example, the Pleiades (located within Taurus) was apparently part of the Zodiac in the Akkadian calendar
01. Over much longer time spans, the ecliptic itself slowly precesses as the Sun orbits the center of the Milky Way Galaxy, but such changes can be neglected for present purposes. A thousand years may seem long to us, but in the life of the Solar System and the Earth, it is just a moment!

Precession of the Equinoxes. The precession of the equinoxes is a clockwise rotation of the Zodiac Clock with the passage of years. This is due to several processes. The main contributor is precession of the earth's axis (Figure 1a), which has a period of about 25,771 years. A secondary contributor is the perihelion precession of the earth's elliptical orbit around the Sun (Figure 1b), a period of about 112,000 years. In the long run, measured by millions of years, the Ecliptic itself also precesses very slowly. On top of these precesssions, the earth wobbles a bit due to the fact that it is not a perfect sphere, and so gravitational pull from the Sun and Moon result in a slight wobble in the Earth's axis.

The sky chart program
Cartes du Ciel (Version 3.6) plots star positions taking into account the effects of these precessions over time (animation: The Zodiac Cycle -- mp4, 1.4 Mb). Each frame of this cycle shows the year in which the zodiac passes from one sign to its neighbor. The complete cycle begins with the Taurus Rising in
27,508 BC and ends with Taurus Rising in 11,092 AD.

Earth Precession from Wikipedia Perihelion precession from Wikipedia
Figure 1a
Precession of the Earth's polar axis
Period about 25,771 years
Source: Wikipedia
Figure 1b
Precession of the Earth's Orbit (Perihelion Precession)
period about 112,000 years
Source: Wikipedia

The Zodiac Clock.
The Zodiac Clock (Figure 2) marks the changes in the Constellations through the year. The clock has the Winter Solstice at the 12 o'clock position, (nominally at December 21), rather than at the beginning of January. The ecliptic forms the outer circle of the zodiac clock.

The Vernal Equinox (Spring equinox) heads the Zodiac, so that (from Figure 2) the calendar is presently moving from Pisces to the Age of Aquarius. Around the change of the calendar, 1 AD, the zodiac calendar was moving from Aries to the Age of Pisces, where it has been for the 2,000 years of the current era.

Zodiac - Calendar 2000
Figure 2
Zodiac Clock in AD 2,000


As a result of the precession of the equinoxes, the zodiac constellations gradually change their position in the Zodiac Clock. An animation of the zodiac clock over a full cycle between 11,000 AD and 27,000 BC is here: gif image (5.0 Mb)  or mp4 movie (2.2 Mb)
02. Sky charts for this cycle are also available as an mp4 video (1.4 Mb). These sky charts are for the years that mark the changes in the constellation at the time of the Fall equinox (September 21 at 6 AM). Figure 3 shows one frame of this video, the time that the sign of the zodiac at the Autumnal equinox changes from Aries to Taurus03.

Taurus Rising, 11,092 AD
Figure 3
The Zodiac Cycle
Autumnal Equinox (September 21)
This Image: Taurus Rising, 11,092 AD
Source: Animation The Zodiac Cycle (mp4, 1.4 Mb)


Remark. Many (perhaps most) treatments of the Zodiac precession
04 only consider precession of the Earth's axis. The Cartes du Ciel program also considers perihelion precession. This additional effect means that the two methods will differ by one zodiac sign every (112,000-25,771)/12 = 7,185 years. Thus one would expect (neglecting other lesser effects) that over 7,000 years the two methods would differ by about one sign. Figure 4 illustrates this for 7,000 BC and 14,000 BC showing differences of (about) one and two zodiac signs. The right-hand clocks in this Figure are computed using Cartes du Ciel. This is the principle reason why some analyses of the Lascaux cave art assume that the Sun is in Taurus at the Fall Equinox, whereas in fact Taurus marks the Winter solstice (see the bottom row which corresponds to the 15,300 BC date of the cave paintings. For a fuller discussion of this see Astronomy at Lascaux Cave.

Polar only vs Polar + Perihelion
Figure 4
The Zodiac Clock:
Effect of adding Perihelion Precession to Polar Precession


fractal

FOOTNOTES

* The background is an astrolabe used by Tycho Brahe to measure star positions in the sixteenth century AD. This illustration is from Tycho Brahe, Astronomiae Instauratae Mechanica:
 
Brahe Instrument

^n01 See discussion on the Babylonian Zodiac.

^n02 
The Zodiac Clocks for years 11,000 AD to 27,000 BC are listed in the following table. These are the individual frames of the zodiac clock animation -- gif image (5.0 Mb)  or mp4 movie (2.2 Mb).

Zodiac Clocks 11,000 AD to 27,000 BC
11,000 AD large
10,000 AD large
09,000 AD large
08,000 AD large
07,000 AD large
06,000 AD large
05,000 AD large
04,000 AD large
03,000 AD large
02,000 AD large
01,000 AD large
00,001 BC large
01,000 BC large
02,000 BC large
03,000 BC large
04,000 BC large
05,000 BC large
06,000 BC large
07,000 BC large
08,000 BC large
09,000 BC large
10,000 BC large
11,000 BC large
12,000 BC large
13,000 BC large
14,000 BC large
15,000 BC large
16,000 BC large
17,000 BC large
18,000 BC large
19,000 BC large
20,000 BC large
21,000 BC large
22,000 BC large
23,000 BC large
24,000 BC large
25,000 BC large
26,000 BC large
27,000 BC large


^n03 The individual frames of the The Zodiac Cycle (mp4, 1.4 Mb) are as follows.

The Zodiac Cycle (Fall Equinox)
11,092 AD: Taurus Rising
8,884 AD: Gemini Rising
6,695 AD: Cancer Rising
4,500 AD: Leo Rising
2,280 AD: Virgo Rising
260 BC: Libra Rising
3,638 BC: Scorpio Rising
7,088 BC: Sagittarius Rising
11.008 BC: Caparicorn Rising
14,285 BC: Aquarius Rising
17,348 BC: Pisces Rising
22,072 BC: Aries Rising
27,508 BC: Taurus Rising

Each sky chart marks the rise of a new constellation into the position of the Autumnal Equinox, September 21 at 6:00 AM. The sky chart is viewed from Lascaux cave at latitude 45° 2' 57" N and longitude  1° 10' 34" E.

Each zodiac sign has a 30° sector of the zodiac clock, and the "rising" of a sign is marked by the rising of a star that is on (or very near to) the ecliptic at the 30° sector boundary. The stars and their proper motion as determined by the Hipparcos Catalog, are shown in the following table, selected for position close to the ecliptic together with small proper motion.

Rising Stars on September 21, 6:00 AM
Sign rising
Star
Distance (ly)
Proper Motion (mas)*
Year rising
(minus = BC)
Taurus 13 Tau 543.6 12.3 11,092
Gemini HD39155 572.2 12.0 8,884
Cancer HD64959 604.0 17.0 6,695
Leo Nu Leo
501.8 30.5 4,500
Virgo HD103485 5,436 23.1 2,280
Libra
HD120622 3,261
5.0
-260
Scorpio
HD139486 472.7 25.0 -3,638
Sagittarius HD161664 2,509 10.0 -7,088
Capricorn HD191536 881.5 29.0 -11,008
Aquarius HD208506 366.5 25.5 -14,256
Pisces HD222754 959.3 4.0 -17,348
Aries HD10894 906.0 12.2 -22,072
Taurus 13 Tau 543.6 12.3 -27,508
* mas = Milli arc seconds per year. The Hipparchos data is accurate to within 1 mas. Over 30,000 years ±1 mas ~ ±1/2 arc minute. The resolution of the sky charts is about 10 arc minutes per pixel, or 20 mas. Listed proper motion results in 1-2 pixel error in the determination of horizon rise time.

^n04 See, for example The Grand Ages and the  Coming of Aquarius which determines the "ages" of the various signs of the zodiac (apparently) using only precession of the earth's axis, and neglecting perihelion precession. The errors increase with distance in the past. For example that reference places the spring equinox in 13,000 BC in Virgo whereas it should be in Cancer. Most other online references to Zodiac signs in the distant past also neglect perihelion precession.

Note (12/7/2012) According to a paper on Anomalous Precessions, The relativistic precession of the Earth's orbit is 3.8345 arc seconds per  century, or 1 minute in 15.67 centuries. Thus in 15,300 BC the perihelion precession of the Earth's orbit amounts to 10 arc minutes -- 3 pixels at the resolution of most of the sky charts shown here. I don't know if the quoted number of 112,000 year period for the earth's perihelion precession includes this relativistic effect, which would amount to 71.58 arc minutes, or about 1.1 degree.



LECTURES ON THE CREATION NARRATIVE
 
A. THE SCIENTIFIC BASIS FOR THE CREATION NARRATIVE


Part I    Genesis 1: Creation of the Universe (HTM - Slides and Text) Audio  PPT

Part IIA   Genesis 2: Creation of Bacteria (HTM - Slides and Text)  Audio-A  Audio-B  Audio-C  PPT

Part IIB   Genesis 3: Creation of Eukaryotes (HTM - Slides and Text) Audio  PPT

Part III     Genesis 4: The Creation of Man (HTM - Slides and Text) (Audio not available) PPT
              Supplementary Lecture: A Sky Map at Lascaux Cave (HTM - Slides and TextPPT

B. THE BIBLICAL ACCOUNT OF THE CREATION NARRATIVE

Part I -- Day One to Day Four (HTM - Slides and Text) PPT 

Part II -- Day Five and Day Six (HTM - Slides and Text) PPT 
     
Part III -- The Creation of Man (HTM - Slides and Text) PPT 


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Update April 14, 2016 The Lascaux Sky Chart