1. Earth’s Tilt and Rotation
Seasonal Changes
Earth’s Tilt and Rotation

2. Axis:
The imaginary line that runs through the poles at a tilt of 23 ½ degrees.
The axis NEVER changes its tilt direction. It remains at the same tilt as the earth revolves around the sun.
Because the earth spins on this tilted axis all parts of the earth DO NOT receive the same amount of sunlight.

3. Revolution:
The movement of the earth around the sun. (Takes 365 days and 6 hours) to make 1 revolution.
The revolution and axis tilt determine the seasons of the year.
March 21st/22nd the sun is directly over the equator.

4. March 21st/22nd Equinox The sun is directly over the equator.
The number of daylight and night time hours are equal (12 and 12)
This marks the beginning of Spring in the Northern Hemisphere and the Beginning of Fall in the Southern Hemisphere.

5. September 23rd Equinox: The sun is directly over the equator again.
This marks the beginning of Fall in the Northern Hemisphere
Also marks the beginning of Spring in the Southern Hemisphere.

6. June 21st/22nd Solstice
The sun is directly over the Tropic of Cancer (23 ½ degrees N)
In the Northern Hemisphere this is when there is the greatest amount of daylight hours and marks the beginning of summer.
Southern Hemisphere is where there is the shortest amount of daylight hours and marks the beginning of winter.

7. December 22nd Winter Solstice
The sun is directly over the Tropic of Capricorn (23 ½ degrees S)
Northern Hemisphere has the least amount of daylight hours and marks the first day of winter.
Southern Hemisphere has the most amount of daylight hours and marks the first day of summer.

8. The Poles

9. North Pole
At the North Pole the sun never sets between March 20th–September 23rd.
There is constant daylight 24 hours a day.

10. Fortress of Solitude

19. South Pole At the South Pole it is reversed.
September 23rd-March 20th the sun never sets. (Meaning Constant Daylight)

20. THE POLES (BOTH) Midnight Sun is the term for constant daylight.
For 6 months a year there is either constant darkness or constant daylight.
Midnight Sun is the term for constant daylight.

21. Effects of Midnight Sun
Constant sun or constant darkness alters lifestyles in terms of:
Food expenses
Human internal functions
Electric bills
Human mental state (State of mind)