Astronomer Phil Plait offers a Crash Course in Astronomy on YouTube and, so far, the episodes are fast-paced, informative, and highly entertaining.

Episode #2 is devoted to “Naked Eye Observations,” which simply refers to looking at the sky without the aid of a telescope.

In the introduction, Phil says, “That’s how we did astronomy for thousands of years and it’s actually pretty amazing what you can figure out about the universe just by looking at it.”

It is becoming increasingly clear that ancient American Indian cultures, such as the Hopewell, paid close attention to the sky and, of course, they had no telescopes. So the program helps us understand how and what they could have learned based only on careful observations made with the naked eye.

At one point Phil says that “Polaris will always point you towards North.” I suppose that’s true for certain definitions of “always,” but it certainly did not point to the North for Ohio’s Hopewell astronomers.

Due to the wobble of the Earth’s axis, the North Pole doesn’t always point to the same place in the sky. Two thousand years ago, Polaris wasn’t the North Star. In fact, there was no pole star at all back then – just as there is no South Star today.

The late N’omi Greber took me into the Cleveland Museum of Natural History’s planetarium one afternoon several years ago and wound the sky back two thousand years for me, so I could see the sky as the Hopewell would have seen it. It was very cool! Instead of a North Star, there was large, dark area around which the other stars and planets appeared to rotate.

I recommend watching Crash Course Astronomy just for the fun of it, but also for the insights episodes like this one offer into what ancient cultures could have learned about the heavens using only their naked eyes.

It’s actually pretty amazing!