Did you know that the upcoming total solar eclipse is intimately connected to the Octagon at the Newark Earthworks?

East of Columbus sit the Newark Earthworks, designed and built by those we call the Indigenous Peoples of the Hopewell Culture, who thrived throughout the Midwest around the years 1-400 CE. The Newark Earthworks are one of the earthwork constructions that were recently enrolled as a UNESCO World Heritage Site, now called the Hopewell Ceremonial Earthworks. They have been recognized as a “masterpiece of human creative genius.”

Another component of the Hopewell Ceremonial Earthworks is at Fort Ancient near the Little Miami River, and the remaining components are sites around Chillicothe along the Scioto River. All of these sites show that these Indigenous Peoples were experts at observational astronomy, for the Earthworks are designed and built to recognize the movements of the heavens. For instance, there is good evidence for a Great Hopewell Road that ran from Chillicothe to Newark and aligned with the Milky Way at the summer solstice. These were special locations.

One of the most remarkable things about the Octagon portion of the Newark Earthworks (pictured above) is that this monumental structure, encompassing over 70 acres, was designed to capture the complex motions of the moon. The main axis of the Octagon points in the direction of the northernmost moonrise, but the Octagon also encodes other elements of the moon’s motion.

Just as sunrises occur in the southeast for winter and northeast for summer and move from one to the other in an orderly fashion, so too do the moon’s rise points swing from southeast to northeast and back again. This sweep of moonrise locations is distinct from the changing phases of the moon. But there is a third, additional motion to the moon: the scope of that sweep changes over an 18-19 year period in such a way it is at its widest for about a year, with maximum widths peaking around the spring and fall equinoxes of that year. This is called a Major Standstill. When the scope of that sweep is at its narrowest, those minimum widths also last about a year, and bottom out around the spring and fall equinoxes at that time. This is called a Minor Standstill.

The intricacies of these lunar motions occur because the orbit of the moon around the earth is tilted in relation to the orbit of the earth around the sun. While the Indigenous Peoples of the Hopewell Culture were probably unaware of orbital dynamics, it is the repeating pattern at those equinoxes, for both the Major and Minor Standstills, that they would have picked up on.

We are now at a Major Standstill. This fall we will be seeing the northernmost moonrise appear directly along the axis of the Octagon. The Ohio History Connection has scheduled Open Houses at the Octagon highlighting some of these alignments. One set will be on April 14 and 15 (which is near the spring equinox), and another set will be on October 20 and 21 (just past the fall equinox).

But what does this have to do with the upcoming eclipse on April 8?

As the moon in its orbit passes through the plane of the earth’s orbit, there is the potential for an eclipse, either solar or lunar. It happens when the line of intersection of the planes of the earth’s and moon’s orbits point at the sun, which happens every 173.3 days or so. And the orientation of eclipse line is driven by dynamics similar to those that make the Standstills align with the equinoxes. That means that, during the Standstills, there is another pattern that makes eclipses also occur near the equinoxes. (Further, midway between the Standstills, eclipses occur around the time of the solstices.)

It is thus no coincidence that both the April 8 eclipse and an Octagon alignment are occurring so close to the Spring Equinox.

Being the closely-observant astronomers that they were, the Indigenous Peoples of the Hopewell Culture almost assuredly were aware of this. They may not have used this knowledge to predict eclipses, but they would certainly have been aware of when to look for them. In fact, in the fall of the year 14, there was a full blood moon lunar eclipse the week before the maximum northernly moonrise.

Maybe this celestial event helped spark the blossoming of the Hopewell Culture?

We are not yet done with eclipses related to this maximum. Next spring we, too, shall see a full blood moon lunar eclipse. It will occur on March 14, just a week after another alignment of the Spring moonrise with the axis of the Octagon. Our awe at these events is sure to closely match that of those other Peoples nearly 2,000 years ago.

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NASA’s website has catalogs of solar eclipses and lunar eclipses.

In 2009, Robert Neinast participated in a “Walk with the Ancients” sponsored by the Newark Earthworks Center at OSU-Newark, which was a week-long pilgrimage from the Chillicothe Earthworks to the Newark Earthworks along the Great Hopewell Road. This sparked his interest in using his physics degrees to find out more about their astronomy.