How does the Earth move?

How does the Earth move?Objectives

EEn.1.1.2.C. Explain precession and its effect on the seasons

EEn.1.1.2.D. Explain nutation and its effect on the seasons.

Agenda

IN: Drawing Earth’s MotionTHROUGH: Precession/Nutation NotesOUT: Lesson ReflectionPRACTICE: Making Models

Notebook

Title: Precession and NutationDate: 2/28/13Pages:

Input: Left Top

• Draw a picture of the 2 main motions of the Earth (rotation and revolution).

So what does precession look like?

• http://www.youtube.com/watch?v=0qHjtp4cdCA

• The Earth’s axis is tilted at a 23.5º angle

• Precession: the change in direction of the Earth’s axis, but without any change in tilt-Like the wobbling motion of a spinning top

• 1 precessional cycle: approximately 26,000 years

• Minor effect on the seasons

The North Star

• Our North Star is currently Polaris

• Because of precession, in 13,000 years our North Star will be Vega

• Nutation: The wobbling/swaying motion during the precession of our axis.

• This causes a 1 degree change in the tilt of the Earth’s axis.

• No effect on the seasons

Output (Left Bottom)

• Reflect on what we’ve learned today by finishing the following sentences.

– Today, I learned …– I was surprised to find …– I wonder what would happen if…– The important thing about …