1. The Reason for the Seasons
Aim= What action is responsible for seasonal changes?

2. 1. Earth’s Tilt Earth is tilted 23.5 degrees.
As Earth is revolving around the sun the northern hemisphere is pointed toward the sun in the summer and away in the winter.

3. Tilt of the axis always stays the same

4. 2. The Sun’s Apparent Movement
In the winter the sun’s path across the sky is very low.
In the summer the sun’s path is very high.
This is why the days are longer in the summer and shorter in the winter.

5. The Seasons

6. 3. The Equinoxes and the Solstices in the Northern Hemisphere
The longest day is June 21st (summer solstice)
The shortest day is December 21st (winter solstice)
When there is 12 hours of daylight and 12 hours of nighttime those days are March 21st (Vernal Equinox) and September 23rd (Autumnal Equinox)

9. Changing Altitude of the Noon Sun
LONG ISLAND, NEW YORK

14. 4. Angle of Insolation Insolation- incoming solar heat
The higher the sun is in the sky the more intense the insolation will be.

15. 5) Zenith The sun will be at your zenith:
At the equator March 21st and September 23rd (equinoxes)
Tropic of Cancer June 21st (summer solstice)
Tropic of Capricorn December 21st (winter solstice)

16. So what is responsible for the seasons?
Earth’s Revolution around the Sun!
The tilt of Earth’s Axis!