Model of Universe
Many students pick science stream for their high school, without really understanding what science really is. To provide a perspective, let us discuss the model of universe during ancient Greek period (at the time of Aristotle). We call this model as: Early Geocentric Model As per early model, the universe is made up of 5 basic elements - Earth, Water, Air, Fire, Ether - in that order of rarity (rarity is inverse of density - more rare = less dense) The arrangement is such that - earth is at the center, then water, then air, then fire. After fire all heavenly bodies are attached on their own celestial spheres. These celestial spheres are hollow concentric shells, enveloping the earth. The outer most celestial sphere comprises of starts visible in the night sky through the naked eye (without any telescopic equipment). These stars seem to move throughout the night as if they are rigidly attached to an invisible bowl that rotates around a fixed pole in the sky - called the North/Sout...