The title plays on the famous idea that men and women come from different planets, then quietly corrects it: both are from Earth. That sets up the tiny three-line poem that follows, where the speaker is looking at the moon and talking with his wife at the same time.
The word "mathematical" is a surprising way to describe the moon. It suggests something precise and measurable, an orbit that can be calculated. Yet the second half of the poem is a simple human conversation, which can't be calculated at all. The dash between them works like a link, as if the two things are happening side by side, or even as if the talk is part of the observation.
The mood is calm and warm. The speaker doesn't argue with anyone or make a big point. He just sits in a shared, ordinary moment, and the title's gentle joke suggests that closeness comes from a common ground rather than from being opposites.