Earth and Moon
How do the sun, earth, and moon interact?
The Moon
Seeing the Moon
The Moon does not produce its own light, despite the fact that it is the second brightest object in our sky (after the Sun). It reflects light from the Sun back at the Earth. Because the Moon's period of rotation is the same as its period of revolution around the Earth — 27.3 days — the Moon always shows the same side to the Earth. Therefore, we are unable to see the other half, the "dark side" of the Moon, with our naked eye. Fortunately, we have seen images of this part of the Moon, taken via satellites and spacecraft that travel to the "dark side."
Moon Phases
The Moon appears to go through phases in the course of a lunar month, which is actually 29.5 days, because it revolves around the Earth so we see different portions of the half-lit side.. The eight phases of the Moon are: waxing crescent, first quarter, waxing gibbous, full Moon, waning gibbous, third quarter (last quarter), waning crescent, and new Moon (not visible).