Why moon appears smtimes half n smtimes full ,is it sun which covers moon?
As others already stated Moon is a sphere (ball like) shining the sunlight and its other half behind in dark. In its orbit around Earth, at different angles we see the illimunated portion and unilluminated portions that appear to us as different phases. As Celith7 claimed it is not beacuse Moon enters Earth’s shadow that is the cause of its dark portion. Getting into Earth’s shadow is a phenomenon, rare enough to be called (Lunar) Eclipse. I suggest a small experiment that you can do at no cost. Place a lighted ‘lamp’ in a dark room on a stool. That is your Sun. Stand at some distance holding a rubber ball (Moon-like white one is preferred) to take it around you(rotate on your heel). Note how the ball’s lighted and dark halves appear to you (being the Earth here). Most such questions are easily resolved by such no-cost experiments.
The Moon is a sphere which travels once around the Earth every 29 days. As it does so, it is illuminated from varying angles by the Sun. At New Moon, the Moon is between the Earth and Sun, so that the side of the Moon facing towards us receives no direct sunlight, and is only lit by dim sunlight reflected from the Earth. As it moves around the Earth, the side we can see gradually becomes more illuminated by direct sunlight. After a week, the Moon is 90° away from the Sun in the sky and is half illuminated, what we call First Quarter because it is about a quarter of the way around the Earth. A week after this, the Moon is 180° away from the Sun, so that Sun, Earth and Moon form a line. The Moon is fully illuminated by the Sun, so this is called Full Moon. The Earth’s shadow points towards the Moon at this time, but usually the Moon passes above or below the shadow and no eclipse occurs. A week later the Moon has moved another quarter of the way around the Earth, to the Third Quarter pos
