What? This makes no sense at all.
The Moon appears to change shape because we see different amounts of the lit part as the Moon orbits Earth. From Earth's perspective, we see varying amounts of the illuminated part of the Moon.
Helpful:
Cures for disease's
Helps us learn about everything around us.
Harmful:
Chemical Warfare
New atomic bombs etc...
A good answer would be "caste". A caste system is the social hierarchy in India in which people are first assigned one of the four main castes (scholars, warriors, farmers, servers) and then additionally often also to smaller castes (farmers of rice, of bananas). The social mobility is very low.
