Hopewell Moonset

Sunday and yesterday were two of the scheduled open houses at the Octagon of the Newark Earthworks. What that means is that the golf course on the site is closed and the folks of the Newark Earthworks Center put on tours for the public of the site. These are always interesting and fun—I always learn something new every time I go.

This was also a very interesting time, almost, to be there.

At the beginning of the year, in Hopewell Moon, I tried to describe the orbital dynamics of the moon and how that is reflected in what we see here on the earth. In that blog entry, I watched (and photographed) the moon rising from near the center of the Great Circle (which is another component of the Newark Earthworks).

But it is really the Octagon and attached circle that are really aligned with the Moon’s celestial peregrinations. This was first pointed out in a 1982 paper by Earlham College professors Ray Hively and Robert Horn, Geometry and Astronomy in Prehistoric Ohio. The main axis of the Octagon is perfectly aligned with the northernmost rise of the moon in its 18.6 year cycle.

It also turns out that there are alignments, though, with what is called the Minor Lunar Standstill, when the northern rises of the moon are at their southernmost points. Let me try to show that with a graph.

If you were to plot where the moon rises every day/night, it would vary from north to south and back to north again over a 27.2 day period (this is very similar to what the sun does over a full year). But if you looked at only the northernmost rise each month, it would look like the following graph:

The Maximum Moonrise Pattern

[Click on all the pictures to enlarge them.]

The x-axis shows the number of months that have passed, starting in the year 194 (when the Hopewell would have been at the Octagon). The y-axis shows the angle of the moon north of east. Over the 18.6 year cycle (approximately 250 lunar cycles), you can see how it goes to a maximum (in the year 200) and then goes to a minimum (in the year 210), and then starts all over again.

Right now was are fast approaching that minimum northern rise (similar to what happened in the year 210).

Actually, if you enlarge the above graph for only right around now, and include all of the moonrises, you get this graph:

The Full Moonrise Pattern

Here, the x-axis is in days from the starting point (in the year 2013) and again the y-axis is the degrees north or south from due east. You can see the monthly cycles of the moon going north and south. The parts that correspond to the previous graph are the high points at the very top of the graph. You ought to be able to see that they are very slightly concave (cupped up).

The bottom of the cup is what the Octagon is also aligned with.

You can see those alignments using my favorite LiDAR data processing. The Octagon shows up very nicely on LiDAR data (particularly if you process the heck out of it). Here is that LiDAR image, with the various alignments overlaid onto it.

The LiDAR Octagon and Circle

You might notice that the north rises and the south sets pretty much point in opposite directions (to within about half a degree), as do the north sets and south rises. That means that if you want to see an alignment, you can look the opposite direction for the opposite of a rise or set.

There is one problem though. Did I mention that a golf course was built over the Octagon? Golf courses have lots of trees on them. That means that most of those alignments are obscured by those trees. And that makes it tricky to see anything, and least when the moon gets near to the horizon.

Here, for instance, is the view down one of the legs of the Octagon for the minimum southern moonset. That tree right in the middle is a bit of a problem.

Lost Horizon

(It’s even more of a problem once it gets leaves on it.)

[By the way, if you look really, really closely, you can see the moon in the upper right corner.]

When the Octagon was built and used, this area was a treeless prairie (probably maintained that way by the Hopewell inhabitants using periodic fires), so you could see to the distant hills near the horizon, and that would affect exactly where the moon would appear during a moonrise.

We can actually use LiDAR data to figure that out, too, and know just how much the hills raised the horizon. Here’s a graph that shows the elevations along a line running from the northernmost leg of the Octagon, pointing to the northeast.

Line-of-Sight Topography Beyond the Northern Leg of the Octagon

The vertical scale is feet above sea level, the horizontal scale is the distance in feet. Obviousl, those two peaks to the far right would be obscured by the one at around 23,000 feet. That’s the hill hightop that would define where the horizon was: 0.46°.

Anyways, during the Sunday open house, the moon was about two days past a minimum moonset, so the alignment wasn’t perfect, but it was still pretty good. There was a moonset at around 1:15 in the afternoon. I wanted to see what I could get.

Here’s a picture across the corridor between the circle and the Octagon.

Corridor Alignment

You can see that the alignment would have it coming down at the opposite corner. The moon (you can see it as a half-moon in the upper-left corner) is coming down to the right at about a 45° angle, so you can see that it won’t line up quite right, but that is because of the two day delay. Unfortunately, I don’t have any pictures with the moon lower in the sky because those clouds to the right moved in to obscure it.

The tours started after I took that picture. The tour guides tell a lot more of the history (and a lot less of the moon stuff—they have to make it comprehensible, after all).

Here is the tour in the center of the Octagon. Tour guide Jeff Gill (on the left) is listening along with the rest of us as Peter Dunham (on the right), a professor from Cleveland State University, discusses what the Hopewell might have been doing with it and how it might have fit into their cosmology. (Another cool thing about the tours is how experts also come on them and contribute their knowledge to the rest of us.)

On the Tour

In the past I’ve been guilty of calling the Octagon a “lunar observatory”. That is just totally inadequate and inaccurate. It’s not as if a few priest-astronomers would go there on given days, look up at the sky, and make a check-mark in a book: “Yup. The moon did what it was supposed to do today.”

In all likelihood, the Octagon area was a sacred space reflecting their cosmological view of the world. I wonder if it was considered their gateway between their lives on the earth and spirit lives in the sky. The Octagon could have been that gateway writ large.

Did I mention how big the Octagon is?

That circle is 1,054 feet across. It is a BIG space. And what might be the purpose behind constructing such a big space?

Professor Dunham gave some hints.

You may not be aware that the game of lacrosse is based upon a similar game played by American Indians that existed throughout the continent. Painter George Catlin painted one of those games played by the Choctaw in the early-to-middle 1800s.

Ball-play of the Choctaw—Ball Up

[Photo from Wikipedia Commons. Click for really, really big version.]

Is that space big enough for you?

On top of that, the game had cosmological significance for the players. It was a way to honor their creator. (Ok, no cracks about the religious overtones of modern games like football—I do live in Ohio State Buckeye territory.)

It is entirely plausible (and I think quite likely) that a space like the Octagon was a playing field with the lunar alignments there to emphasize, or maybe resonate with, the patterns of creation displayed so boldly in the sky by the moon. I love it.

By the way, I also have to show another of Catlin’s paintings:

Ball Players

[Photo from Wikipedia Commons.]

From my point of view, of course they would be playing barefoot. How else to be connected properly to the earth while playing for the sky?

[Yes, I do notice that many, but not all, of the players in the larger painting seem to be wearing moccasins. Those may, however, be ankle decorations or skin art. Regardless, it is quite possible that features of the game could have changed over so many years.]

Back to the tour . . .

Here we are heading through the connecting corridor from the Octagon to the circle.

Through the Corridor

[Photo credit: Jeff Gill.]

You can see me on the left with Brad Lepper, Curator of Archaeology for the Ohio History Connection.

I like this shot from right at the entrance to the circle.

The Three Expertos

It has Peter Dunham on the left and Brad Lepper listening to Jeff Gill.

By the way, this is pretty much looking in the opposite direction from the alignment photo I showed you earlier. For that picture I was standing near where the baby carriage is on the walkway in the distance.

Oh, yeah. One more thing.

Saturday, the day before the open house, was even closer to the alignment. It was also a spectacularly clear day. In addition, the moon was slightly fuller and thereby more visible.

So I got out there and was able to make an animated gif of the moonset. With me was photographer Tim Black.

We stood at the northernmost point of the Octagon and looked along the mound wall to the southwest. (Officially, this leg is for a northern moonrise in the east, but as I mentioned earlier, it is also really close for a southern moonset in the west.) The only real problem with the animated gif is that the moon disappears in the horizon haze about 6-8° above the horizon. (Also, right near the end, a cloud screwed up my exposures.)

The Descent of Moon

[To see it properly, look to the upper left when the gif starts or re-starts. You can then follow the moon down. It’s also better if you click on it for a larger version.]

When I analyze the photos and extend the path of the moon, it ends up landing just a little bit to the right of the end of the mound, right where it is supposed to.

Tim Black brought along his camera that takes infrared shots. That cuts through the haze much better (that, and he is a much better photographer than I am).

Moonset Alignment

[Photo credit: Tim Black.]

If you look carefully you can just barely see the moon in the upper left about to disappear behind the trees.

Isn’t that awesome?

There are two more open houses this year: Tuesday, May 26 and Sunday, October 11. Why don’t you put them on your calendar right now and make sure you come out to visit on those dates?