Since the earth's shadow creates the crescent moon why does the moon not look like a crescent after 7 days?

Answer 1

Your assumption is not correct. The crescent moon has nothing to do with the shadow of the earth falling upon the moon. The moon being obscured by earth's shadow is a relatively rare event, and it is known as a lunar eclipse. Furthermore, during a lunar eclipse the passing earth shadow does not show as a sharp edge on the moon's surface. The crescent moon shapes that you typically observe over the course of a month are a result of the fact that earth's view of the moon is changing, and as our view changes, we see more of the lit surface of the moon or less, depending on where we are in the month. The moon orbits the earth once every month in its west-to-east orbit. During the same time, the earth is spinning on its axis west-to-east once every 24 hours. This is why the sun, moon and stars all appear to rise in the east. During our nighttimes, we watch the moon slowly progress from lunar noontime (at the time of the full moon, for an observer at the center of the moon's face) to lunar midnight (at the time of the new moon when the view of the moon is obscured by the brightness of the sun) and back to lunar noon at the next full moon. We can sometimes observe the very fine first crescent of the moon shortly after the time of the new moon, after sunset. The moon's orbit around the earth is not in the same plane as the earth's orbit around the sun. This means that the earth's shadow never touches the moon during most months. Now and then, and only at the time of the full moon, the earth's shadow will pass over some or all of the full moon during what is called a lunar eclipse. These eclipses last for a few hours at most.

Answer 2

The Moon's position in its orbit changes relative to the Earth and the Sun, leading to different phases. After 7 days, the angle between the Earth, Moon, and Sun results in the Moon appearing as a different phase than a crescent. This change in angle causes different amounts of sunlight to be reflected back to Earth, creating the various phases of the Moon.