Each day (night?) a little more of of the moon's surface is illuminated by the sun; thus it becomes brighter and changes from a thin crescent to a full circle of light. It takes about 2 weeks (a...
The Moon itself doesn't change at all. What we see as the "phases" of the Moon are simply the month-long days and nights on the Moon's surface. The light comes from the Sun, over THERE, while we see...