An interesting thing happens if you move your perspective from the Earth to the Moon. The phases of the Moon we see from Earth depend on the angle of the Moon and Sun in the sky. But on the Moon, the angles are exactly 180° reversed; at new Moon, when the Moon is between the Earth and Sun, the Earth is opposite the Sun as seen from the Moon. It’s full Earth! All the other phases are opposite too, so when we see a full Moon, a Moon-dweller would see a new Earth, and so on.
Have you ever looked at the thin crescent Moon and seen the ghostly face of the rest of the unlit side? That’s because it’s not really unlit: the nearly full Earth is reflecting sunlight on the Moon, lighting up the otherwise dark part. The Earth is bigger and more reflective than the Moon, so it’s actually 50 times brighter
than a full Moon! This glow is called Earthshine, a term I quite like. Even more poetically, it’s been called “the old Moon in the new Moon’s arms”, referring to the unlit part surrounded by the crescent new Moon’s horns. That’s lovely, isn’t it?
The Moon is one of the most beautiful and most gratifying objects in the sky to observe. It’s different every day! Yet it’s also the same, because we see, more or less, the same half of it, the same face all the time. It’s big and bright, and the features on its surface discernible by eye (and even better with binoculars or a small telescope). As the phases change, inexorably, day after day, the angle of sunlight hitting the surface changes, bringing new things into our view. The motions become comforting, even familiar. It’s a reminder that the Universe may seem strange and complicated and forbidding at first, but over time, as you get outside and experience it, it becomes your neighborhood. Welcome home.