1. Aim: Why do we experience the seasons?
Do Now: As the Angle of Insolation increases,

2. Why were all the Harvard graduates wrong about the seasons?
Video - Harvard Grads about Seasons
Why were all the Harvard graduates wrong about the seasons?

3. Why do the seasons occur?
Tilt of Earth’s axis – (23.5°) – the angle and intensity of insolation vary at different locations
Revolution of Earth around the Sun
Parallelism of Earth’s axis– the axis always points the same direction in space as Earth orbits around the sun

4. How does the Tilt affect the Earth?
Which hemisphere of the Earth is receiving direct rays?
Because the Earth is tilted, the North and South Pole receive different amounts of sunlight (The tilt determines the season).

5. Shortest day of the yearN
Sun’s Direct Rays
Season:
Date:
Hours of daylight North Pole – New York – Equator – South Pole –
Spring
Hours of daylight North Pole – New York – Equator – South Pole – 12
Vernal Equinox 12
March 21 9 12 12 12 24
Winter Solstice
Dec. 21
Equator 0º
Longest day of the year
Aphelion (farthest)
Perihelion (closest)
Tropic of Cancer 23.5ºN
Tropic of Capricorn 23.5ºS
Shortest day of the year
Equator 0º
Summer Solstice
June 21
Hours of daylight North Pole – New York – Equator – South Pole –
Fall
Hours of daylight North Pole – New York – Equator – South Pole – 24 12 15
Autumnal Equinox 12 12
Sept. 23 12 12

6. Shortest day of the yearN
Sun’s Direct Rays
Season:
Date:
Hours of daylight North Pole – New York – Equator – South Pole –
Spring
Hours of daylight North Pole – New York – Equator – South Pole – 12
Vernal Equinox 12
March 21 9 12 12 12 24
Winter Solstice
Dec. 21
Equator 0º
Longest day of the year
Aphelion (farthest)
Perihelion (closest)
Tropic of Cancer 23.5ºN
Tropic of Capricorn 23.5ºS
Shortest day of the year
Equator 0º
Summer Solstice
June 21
Hours of daylight North Pole – New York – Equator – South Pole –
Fall
Hours of daylight North Pole – New York – Equator – South Pole – 24 12 15
Autumnal Equinox 12 12
Sept. 23 12 12

7. 1) Explain what would happen to the seasons if the Earth’s tilt was increased to 33.5°?
Summer Solstice
Winter Solstice
SUN
More Extreme Seasons – Colder winters and Warmer summers
The latitudes of the tropics would increase to 33.5°N and 33.5°S
2) Explain what would happen to the seasons if the Earth had NO TILT (90°)?
SUN
NO SEASONS
Sun’s Direct (vertical) rays will always hit the Equator

8. 3) Explain whether the distance affects the Seasons
Distance does NOT affect the seasons because we are closest to the sun during Winter. (Perheilion)

9. Summary Activity – Stations
For each lettered Earth (A-D), indicate the Season and the Date for the Northern Hemisphere
1) Autumn Equinox ) September 23
1) Winter Solstice ) December 21
1) Summer Solstice ) June 21
1) Vernal Equinox ) March 21

10. Extra Questions
Which diagram most correctly shows the portion of Earth that is illuminated by sunlight and the portion that is in shadow on the first day of summer in the Northern Hemisphere?
Which location on the Earth would the Sun’s vertical rays strike on December 21?

11. Summary Activity – Stations
For each lettered Earth (A-D), indicate the Season and the Date for the Northern Hemisphere

12. Hours of daylight North Pole – New York – Equator – South Pole –
Sun’s Direct Rays
Season:
Date:
Hours of daylight North Pole – New York – Equator – South Pole –
Hours of daylight North Pole – New York – Equator – South Pole –
Hours of daylight North Pole – New York – Equator – South Pole –
Hours of daylight North Pole – New York – Equator – South Pole –