World vs celestial sphere

World

• The Universe: our universe. 

• The Developed World (the developed world). 

• The Industrialized World (the industrialized world). 

• The Third World (the third world). 

• The First World (the first world). 

• Existence. 

• The Fourth World (the fourth world). 

• Earth: the Earth (our earth). 

• The Second World (the second world). 

• The Developing World (the developing world). 

celestial sphere

• the figure of the universe as an imaginary sphere whose center is the Earth 

• An abstract sphere of infinite radius which serves as the imaginary backdrop for celestial objects, and of which the visible sky is one hemisphere.