Full moon, new moon. High tide, low tide. These are dependable rhythms of our planet. It is not surprising then, that news of a “wobble” in the moon’s orbit—one with implications for the growing problem of U.S. coastal flooding — has piqued the curiosity of many. So, what exactly is this “wobble?” The word wobble suggests a breakdown in the regular and predictable motion of the moon and its influence on the tides. This is not the intended meaning, though. What the media has termed the ”wobble” is actually a cycle as regular as the seasons but occurring over decades rather than months. More specifically, the path of the moon’s orbit around Earth is tilted in space and rotates once every 18.6 years with a motion similar to the undulations of a spinning coin just before it falls flat. This motion is more precisely described as lunar nodal precession, and it is most certainly not a new discovery. Astronomers have observed this phenomenon for millennia by documenting gradual changes to the moon’s position in the night sky.