The Origin of the Chaldean Order and Planetary Days of the Week

In this episode I propose a new theory about the origins of the so-called Chaldean order of the planets, as well as the assignment of the seven traditional planets to the days of the week.

In ancient times, a specific sequence of the planets arose known as the order of the seven-zoned sphere, which goes:

Moon, Mercury, Venus, Sun, Mars, Jupiter, and Saturn.

In modern times, this is often called the "Chaldean order", because the 5th-century CE writer Macrobius referred to it as the "system of the Chaldeans."

For a long time, it was mistakenly thought that this meant it came from ancient Babylonian or Mesopotamian astrologers, but we now know there is no trace of it in that tradition.

In Macrobius’s era, the word "Chaldean" had simply become a generic term for "astrologer", so when he refers to it like this, what he really means is "the system of the astrologers."

So, where did this system come from, and when was it introduced?

While historians have long known that this planetary order was popularized during the Hellenistic era, the standard assumption has been that it was first developed by astronomers, or Pythagoreans, or some other group, and then only later incorporated into astrology.

In some academic sources this shift, which radically moved the Sun to the center of the planets, is notably glossed over, largely because scholars don’t really know where it came from or how it happened.

In this lecture, I propose the exact opposite: that this system was actually first popularized, and potentially even invented, by astrologers in Egypt in the 2nd century BCE, starting with the group of texts Hermetic surrounding Nechepso and Petosiris.

From the 2nd century BCE forward, this order became widely adopted across different scientific, philosophical, and religious traditions, eventually becoming the underlying rationale for the names of the seven days of the week.

My primary goals with this episode are to: