Precession of the Equinoxes, page 5

Bring on the Solstice

A precessional calculator

So far we've looked at the solstices only briefly but now we should bring them into the picture. We have seen that, as a result of precession, the equinoxes shift along the constellations of the zodiac. Naturally, the same thing happens to the solstices. Putting these together we can construct a simple diagrammatic calculator to determine which constellation carries the sun on any solstice/equinox in any age. Remember that an astronomical age is assigned the name of the constellation that carries the sun into the dawn sky on the spring equinox. Figure 9 below shows the solstice and equinox markers at the beginning of our current age, that of Pisces.

Solstice/equinox markers for dawning of the Age of Pisces

Figure 9. Solstice/equinox markers for dawning of the Age of Pisces

Go down to any sky

Given that the modern figure for the precessional movement is 1 degree per 71.6 years, we can work out that a 30° zodiacal segment takes 2148 years to traverse, and the whole cycle thus takes 25776 years to complete. The solstice and equinox markers for today are shown in Figure 10 below. From that starting point, working backward, you could "go down to any sky" and calculate the correct set of solstices and equinoxes for any age, like some ancient astronomer-priest. For example, during the period of approximately 8,000 BC to 10,000 BC, the sun on the spring equinox was carried by the constellation of Leo, thus naming the Age of Leo. Some American scientists have calculated, by measuring the amount of erosion it suffered, that the Sphinx in Egypt was originally carved out of the bedrock during the same period. This raises a question about the age of the names of zodiacal constellations, as well as the accepted age of the Sphinx, but that speculation is for others to follow.

  

Solstice/equinox markers for today at the dawning of the Age of Aquarius

Figure 10. Solstice/equinox markers for today at the dawning of the Age of Aquarius

Hotlink to instructions to make your own precession calculator.