1. Reasons for Seasons

2. Earth’s Axis is Tilted!
The Axis is an imaginary line drawn through the planet from the North Pole to the South Pole
Earth’s axis is tilted 23.5 degrees.
Therefore Earth’s axis is not perpendicular to the plane of the solar system.
It is this tilt that allows for seasonal changes.

3. Seasons
Because Earth’s axis is tilted, each hemisphere receives varying amounts of sunlight during the year.
arcticsystem.no

4. Seasons continued
As the Earth travels around the sun, the slant of Earth changes.
Sunlight hits Earth at different angles throughout the year.
This is why we have seasons and variations in the length of day and night.
bbc.co.uk

5. Amount of sunlight and season
Summer in Northern Hemisphere
Winter in Northern Hemisphere
britannica.com
britannica.com

6. Equinoxes
On the autumn and spring equinoxes, there is an equal amount of day and night (12 hours each).
Fall Equinox: September 21 (ish)
Spring Equinox: March 21 (ish)

7. Solstices
On the summer solstice, there is the longest day of the year- when the sun is at its highest position in the sky.
On the winter solstice, there is the shortest day of the year- when the sun is in its lowest position in the sky.
Summer solstice: June 21 (ish)
Winter solstice: December 21 (ish)

8. Distance from the sun doesn’t determine the seasons!
wunderground.com

9. The Sun’s changing position in the sky (why the days are longer or shorter)
bbc.co.uk

10. What about the equator?
The suns vertical rays are located at the equator throughout the year.
This allows the equator to receive 12 hours of sunlight all year.
w3.shorecrest.org

11. What would happen if the tilt was more or less?
hyperphysics.phy-astr.gsu.edu