Imagine a caveman's perception of the full moon rising above the horizon one night while he stands outside of his cave in the summer. There is nothing on earth that is comparable to the compelling radiance of this object that is positioned across the sky at night. What was the Neanderthal's definition of this object? This could explain why the moon is the inspiration behind a lot of folklore, myths, legends, old wives tales and acts of worship.
The first scientific examination of the moon and its phases was done by the Greek in 500BC. Pythagoras, a Greek with interests in philosophy and astronomy intently studied the defining line that is called the terminator that separated the light and dark hemispheres of the moon. He made a correct submission based on his studies of the terminator and how it was curved around the moon, that the moon has a spherical shape.
Several years back in 350 BC, Aristotle continued to expand on the Pythagoras analysis by studying the shadows which the earth cast across the surface of the moon when a lunar eclipse occurred. He opined that the Earth had a spherical shape. However, his premise for this was faulty because he believed that the earth was stationary and that the moon, stars, and sun were in orbit around it. It was also his belief that the moon was translucent and that it travels in a clockwise motion around the Earth.
In the 16th century, the standard understanding of the solar system took a different turn. Nicolas Copernicus, an astronomer in early 1500, created a mockup of the solar system showing a system where the planets including the earth moved around the sun and the moon moved around the earth; all in a circular motion. It was not until a hundred years later when an Italian astronomer Galileo used one of the pioneer telescopes to study the terminator. Galileo gathered from his studies that the surface of the moon was uneven and marked by craters, valleys and even mountains. He made this submission due to the jagged shadows of the waning crescent phase.
These new observations stirred up a revolution. It caused a division; with Galileo and Copernicus remaining staunch supporters of the Aristotelian view arguing that the earth was the center of the universe, the heaven was a place, and the moon has a smooth surface. It took the intervention of telescopes and younger scientists in seeing that the planets including the earth moved around the sun and the moon is a cratered and rough satellite within the orbit of the earth.