AST 301 Lecture Notes - Lecture 1: Gnomon, Astronomical Object
Document Summary
The sun and stars were used to know the time, navigate before maps, and meet at a future time before watches were created. Humans before us had curiosity and were able to recognize patterns in shapes and phenomena. Gnomon- a stick in the ground that the sun casts a shadow on. It is somewhat like a sundial, where the shadow moves as the sun moves. When the sun is south, the shadow on the gnomon is pointing north. The length of the shadow from the gnomon is smallest when the sun is high, and largest when the sun is low. The celestial sphere is an imaginary sphere that stars, even at a different distance, appear to lie on. Think of it as a dome of sky, or an inverted bowl. The zenith is the imaginary vertical line that touches the top of the celestial sphere and is directly above you no matter where you are.
