AST101H5 Lecture Notes - Lecture 1: Retrograde And Prograde Motion
Document Summary
We see only one side of the moon. Commonly interpreted to mean that the moon does not rotate - wrong! If the moon did not rotate, we would see both sides during the month. To keep one side constant facing the earth, the moon must rotate once each orbit. At new phase, the moon can pass in front of the sun, preventing sunlight from earth. Solar eclipse - sun is blocked out by moon. At full phase, the moon can pass through earth"s shadow, preventing sunlight from illuminating the moon. Lunar eclipse - sun - earth - moon. Light is bent by earth"s atmosphere and gravity and directed towards the moon. Blocks out the blue/purple colour of the sun and leaves the red/yellow. A simple diagram of the earth, moon and sun is 2-d. Moon"s orbit around earth is tilted to earth"s orbit around the sun - they do not line up most of the time.