Abri Blanchard Calendar: Five Planets

Liú Xiàng seemed to imply that the five planets were in conjunction, in other words, grouped together in the same area of the sky.

If we view the diagram on the bone as a sky map, we can identify the ecliptic, and the ecliptic pole. The observer is facing south (bottom of the diagram below), with north above and behind her.

Image: Alexander Marshack © Peabody Museum: Annotation: Lynn Fawcett
Image: Alexander Marshack © Peabody Museum: Annotation: Lynn Fawcett

We know that the Earth, the Moon and the five planets all orbit the Sun. It is therefore easy to identify the sun in the centre of the diagram. To construct the ecliptic, we use dot number 70, which is located outside of the main group. The dot can be seen on the photograph of the bone, to the left of the diagonal line, near the centre. A line drawn from dot number 70 passing through the centre of the sun gives us the ecliptic.

We also know that the ecliptic pole is at an angle of 90 degrees to the ecliptic, but at what point does the line intersect with the ecliptic?

For the answer, we must look to the dots with arrows. The arc of each arrow depicts the direction in which the Earth, the Moon and the five planets orbit the Sun. The only exceptions are the five arrows in the bottom right of the image which depict retrograde motion.

When released, an arrow curves around the bow and then flies in a straight line to join two points. The solitary arrow that sits just below the ecliptic is the one that we must ‘shoot’ to get the point of intersection between the ecliptic pole and the ecliptic.

Note that the angle of this new line is at 12 degrees to the ecliptic. 360° divided by 12 gives us the 30 points that are plotted on the bone.

The sun travels just under one degree along the ecliptic each day. To adjust for the difference between the convenient division of the ecliptic into 360 and the actual time that it takes for the sun to travel along its path, there are five distinct dots on the bone plaque that represent the five planets.

The five planets visible to the naked eye consist of the two gas giants, Jupiter and Saturn, and the three terrestrial planets Mercury, Venus and Mars. Rightly or wrongly, this is how I decided which dot represents which planet:

Venus is at its brightest when it is a crescent shape.

Mercury the other inner planet also exhibits phases (changes its apparent shape, when seen from the Earth).

Jupiter is bigger than Saturn.

The placing of the planets in a spiral pattern could also indicate a five day week. 73 cycles of five would give a year of 365 days.

We have now accounted for another seven of the dots identified by Mr Marshack, giving us a total of 39 dots. The remaining 30 dots represent the cycle of the Sun.


Image Credit:

Schematic rendition of the engraved marks on the bone from the Abri Blanchard as determined by microscopic analysis, indicating the differences in the engraving points and the strokes structuring the serpentine form: Alexander Marshack, 1972: The Roots of Civilization: The Cognitive Beginnings of Man’s First Art, Symbol and Notation, p.48, Fig. 9: Weidenfeld and Nicholson: © President and Fellows of Harvard College, Peabody Museum of Archaeology and Ethnology: Courtesy of the Peabody Museum of Archaeology and Ethnology: Peabody ID Number: 2005.16.1.318.57: Schematic Rendition of the Incised Design on a Carved Bone Fragment: https://www.peabody.harvard.edu/