1. SPACE Day/Night and Seasons

2. Objective To model and illustrate how the tilt of the earth rotates on its axis, causing day and night and how it revolves around the Sun causing changes in the seasons

3. How does the Earth move? Long ago, people thought that the Earth stood still while the Sun moved We now know that the Earth moves around the Sun The Earth REVOLVES around the Sun The Earth ROTATES while it revolves around the Sun

4. Day and Night We have day and night on Earth because of the EARTH’S ROTATION – the earth spinning around and around. (1670 km/hr)

5. Day and night

6. It takes 24 hours for the Earth to ROTATE once.

8. The Earth is kept in orbit by the force of… Gravity …and by the fact that is is moving at a high velocity

9. Why are there seasons? Earth not only spins on its axis, it also revolves around the Sun Earth’s trip around the Sun takes 365¼ days, or one year Every 4 years, we add a Leap Day to account for the extra ¼ days Earth's path, or orbit is shaped like an ellipse or a flattened circleorbit The tilt of the Earth is the reason for the seasons

10. The Earth is divided up into the northern hemisphere and the southern hemisphere: Equator Northern hemisphere Southern hemisphere

11. Seasons If the Earth was perfectly balanced, as it is in this animation, we wouldn’t have different seasons and the sun would always rise and set at the same time every day.

12. Seasons Every part of the Earth would receive an equal amount of sunlight as the earth rotated.

13. But the Earth isn’t perfectly balanced, it’s tilted on its axis…

14. …and it’s REVOLVING around the sun.

15. The tilt changes how much sunlight each part of the earth receives. It is this tilt which makes our days longer or shorter and it’s what causes the seasons.

16. Seasons The tilt does not change – it always remains pointed in the same direction As the Earth revolves around the Sun, the tilt sometimes points toward the Sun, sometimes away from the Sun, and sometimes neither away nor toward the Sun

17. Summer season In June, the North Pole tilts toward the Sun. The northern half of Earth (Northern Hemisphere) receives more direct sunlight Daylight hours are longer and temperatures are warmer. June 21 st - Summer Solstice This is our summer What season does the Southern Hemisphere experience in June?

18. Winter season In December, the North pole tilts away from the Sun. The northern half of Earth (Northern Hemisphere) receives less direct sunlight Daylight hours are shorter and temperatures are colder December 21 st – Winter Solstice This is our winter What season does the Southern Hemisphere experience in December?

19. Spring and FallSpring and Fall Seasons In March and September, neither the top or bottom half of Earth is tilted toward the Sun In spring and fall, the top and bottom parts of Earth (Northern and Southern hemispheres) receive the same amount of direct sunlight The amount of daylight is close to 12 hours and the temperatures are more moderate March 21 st – Vernal Equinox September 21 st – Autumnal Equinox This is our spring and fall What season does the Southern Hemisphere experience in March? In September?