AST 101 Lecture Notes - Lecture 2: Depth Perception

• School: Syracuse University
• Department: Astronomy
• Course: AST 101
• Professor: Walter Freeman

Document Summary

They rotate in a circular motion around the sky. You can see about half of it at any given time. It explains a lot of things, but it"s not perfect. All the stars aren"t stuck to a sphere - their distance varies (but we don"t have depth perception for things far away) Key idea 1- the stars are very far away compared to the earth"s motion. It doesn"t matter that the stars are very different distances away (since distance is much greater than our motion) Key idea 2 - it doesn"t matter if the earth rotates or the celestial sphere rotates: relative motion controls speed. The difference of our perspective on the angles of the stars. The further away the starts are from earth, the smaller the parallax angle. We can treat the stars as all rotating together, on an invisible sphere far away. We can expect this to get the stars right and the planets and the sun wrong