1. Earth’s Orbit 4/29/14 IN: What causes the different seasons on the Earth? IN: What causes the different seasons on the Earth?

2. Remember… The axis around which the Earth rotates is tilted by 23.5 degrees with respect to the ecliptic. The axis around which the Earth rotates is tilted by 23.5 degrees with respect to the ecliptic. It is the tilt of the Earth that causes the different seasons. It is the tilt of the Earth that causes the different seasons.

3. The angle of the tilt never changes. The angle of the tilt never changes. It is the direction of the tilt that changes. It is the direction of the tilt that changes.

4. The sun’s rays strike the Earth’s surface at different angles because the surface is curved.

5. Indirect rays – light rays that do not hit the earth straight on.

6. Direct rays – light rays that do hit the earth straight on. Sun's Rays Simulator

7. Seasons Earth-Sun Relations Earth-Sun Relations Earth-Sun Relations Earth-Sun Relations

8. Tilt of the Earth’s Axis The axis around which the Earth rotates is tilted by 23.5 degrees with respect to the ecliptic. The axis around which the Earth rotates is tilted by 23.5 degrees with respect to the ecliptic. It is the tilt of the Earth that causes the different seasons. It is the tilt of the Earth that causes the different seasons.

10. Summer Solstice On June 21, the North Pole points directly toward the sun. On June 21, the North Pole points directly toward the sun. On this day the North Pole has 24 hours of sunlight. On this day the North Pole has 24 hours of sunlight.

11. Summer Solstice

12. Midnight Sun

13. Winter Solstice On December 21, the North Pole points away from the sun. On December 21, the North Pole points away from the sun. On this day, the North Pole has 24 hours of darkness. On this day, the North Pole has 24 hours of darkness.

14. Winter Solstice

15. Equinoxes On March 21 and September 21, neither hemisphere leans towards the sun. On March 21 and September 21, neither hemisphere leans towards the sun. On these days, every place on earth has 12 hours of daylight and 12 hours of darkness. On these days, every place on earth has 12 hours of daylight and 12 hours of darkness.

16. Equinoxes

17. The angle of the tilt never changes. It is the direction of the tilt that changes.

18. Seasons Misconception Many people carry the misconception that the seasons are due to the distance of the Earth from the Sun. However, consider the following facts: Many people carry the misconception that the seasons are due to the distance of the Earth from the Sun. However, consider the following facts: The Earth’s orbit around the Sun is nearly a perfect circle. The Earth is slightly closer to the Sun in January and farther from the Sun in July. The Earth’s orbit around the Sun is nearly a perfect circle. The Earth is slightly closer to the Sun in January and farther from the Sun in July.

19. Seasons Misconception While it is winter in the Northern hemisphere it is summer in the Southern hemisphere. If the seasons were due to our distance from the Sun both hemispheres would have the same seasons at the same time. While it is winter in the Northern hemisphere it is summer in the Southern hemisphere. If the seasons were due to our distance from the Sun both hemispheres would have the same seasons at the same time.

20. * Gravitation 3.8 Home Page — Normal Display * Gravitation 3.8 Home Page — Normal Display * Gravitation 3.8 Home Page — Normal Display * Gravitation 3.8 Home Page — Normal Display

21. OUT: Why do you think it is important to study the Earth’s orbit around the sun?