How Realistic Is the Celestial Navigation in Moon Knight?

The science in a superhero show doesn’t need to be perfectly accurate to be awesome. Really, one of the reasons we like these shows is because they aren’t realistic. However, that will never stop me from using a show to talk about physics.

Let’s look at a scene from Moon Knight, episode 3. If you don’t know anything about Marvel’s newest character from the Disney+ live action series, don’t worry, I can give you a quick intro. Moon Knight is the human avatar of the Egyptian god Khonshu, the god of the moon. This gives him some superpowers, like extra strength and faster healing. But there’s a small problem: The avatar of Khonshu has a dissociative identity disorder. He has at least two different human identities—the mercenary Marc Specter and the businessman Steven Grant.

I won’t include any significant spoilers, but still, use some caution if you are waiting to see this episode, which deals with celestial navigation. I’ll start with some very basic but important ideas about navigating with the stars.

How Do You Find Where You Are?

Today, we usually don’t need to use the stars to find our way around. I mean, just take out your phone; it has a receiver for the Global Positioning System along with an internet connection to download whatever map you need. But before phones and GPS, people still had to get places. One way to do this was to use objects in the sky. Although it is possible to use the sun and moon (and even the planets) for navigation, I’m going to stick with the stars.

If you look at the stars at night, they appear to move. The stars that you see at 9:00 pm are in a different location by 2:00 in the morning. This is not because the stars actually move; it’s because the Earth spins on its axis. Let me draw a super basic example. Suppose you are standing somewhere along Earth’s equator and you look at a star that is directly overhead. If you look again after two hours, it would look like this:

In fact, all the stars in the sky seem to move together, as if they were part of a fixed sphere that has the same center as Earth’s. We call this the “celestial sphere.” I know it’s difficult to visualize, so here’s a picture of a celestial sphere model as used in astronomy courses: