1. Earth Motions

2. Earth Motions 1. Rotation- spinning of the Earth about its axis
Cause of day and night.
Solar day is 24 hours, from noon to noon.

3. Sidereal Day
Earth makes ONE complete rotation (360o) in 23 hours and 56 minutes.
Click HERE for an animation.

4. 2. Revolution- Earth’s orbit about the sun.
Elliptical orbit (not a perfect circle)
Perihelion- the earth is closest to the sun
 Jan 3rd (147 million km)
Earth moves the fastest in orbit
Aphelion- farthest from the sun
 July 4th (152 million)
Earth moves the slowest in orbit

5. Milankovitch Cycles
Long-term earth movement. Can be from 10s of thousands of years to 100s of thousands of years.
Linked with
global climate
change.

6. Earth motions- Milankovitch Cycles
3. Precession- wobbling of the Earth like a top.
one complete wobble  26,000 years (cause of the changing North Star)
Precession does NOT change the angle Earth is tilted, just the
direction it is
pointed.
Does not change
climate, but does
change WHEN we experience seasons.

7. Inclination of the Axis
Obliquity- Earth’s axis changes its tilt from more straight up and down to more tilted.
the Earth’s axis is currently tilted 23.5o from the ecliptic.
changes 22.2 to 24.5 through a 41,000 year period.
Tilt of the Earth is the cause of the Seasons. If you change the tilt then you change the seasons.

8. Eccentricity
Eccentricity- HOW elliptical the orbit of the planet is around the sun.
100,000 year period from high to low eccentricity.
Click HERE for a website review of Milankovitch cycles