What we have learned:
- The eastward-bowing curves of the serpent’s body point to moon rise points on the eastern horizon for the full moons closest to the equinoxes and solstices.
- The fact that the “pointers” are broad suggests they were lunar rather than solar pointers, indicating both the direction of full moon rise and the range of variation in the rise point due to the moon’s complex orbit.
- The head of the Serpent, in pointing near the summer solstice sunset, puts an emphasis on that season, suggesting a practice of conception near the summer solstice for birth near the spring equinox. The fact that it points a little more than a degree south of the actual summer solstice sunset suggests it is marking out an interval (a precise one month interval actually) near summer solstice. Some time during that interval there would be a full moon rise on the opposite horizon at the time of sunset.
- The seeming “solar” alignment feature of the Serpent’s head would then be an actual lunar indicator, used to identify the full moon nearest summer solstice.
So, we suggest that Serpent Mound could have been a Lunar observatory with a specialized application for Native American woman of the tribe, to plan the conception, measure the length of the pregnancy and forecast the time of birth of their children.