1. “Why are there seasons?” GEMS Space Science Unit 2

2. Unit 2 Key Concepts The distance between the Sun and the Earth is so great if you had the model of the Sun, the size of a pea, on drawn on a piece of paper, the Earth would be off the page.

3. Day and Night Cycle

4. Unit 2 Key Concepts Scientists use models to demonstrate ideas, explain observations, and make predictions.

5. Unit 2 Key Concepts Earth travels around the Sun in a nearly circular orbit called an ellipse.

6. Unit 2 Key Concepts The Sun is very close to the center of Earth’s orbit.

7. Unit 2 Key Concepts Patterns of average-temperature change (and seasons) are opposite for the Northern and Southern Hemispheres.

8. Summer in the Northern Hemisphere

9. Winter in the Northern Hemisphere

10. Unit 2 Key Concepts Earth’s tilt does not significantly change its distance from the Sun.

11. Unit 2 Key Concepts Scientific explanations are based on evidence gathered from observations and investigations.

12. Unit 2 Key Concepts For any given latitude, spring and summer days have more hours of daylight, and fall and winter nights are longer.

13. Unit 2 Key Concepts In the Northern and Southern Hemispheres, day-length changes (and seasons) are opposite one another during the year.

14. Unit 2 Key Concepts Day-length changes are more dramatic farther away from the Equator.

15. Unit 2 Key Concepts Earth’s tilted spin axis causes seasonal changes in hours of daylight and night throughout the year.

16. Unit 2 Key Concepts At the beginning of summer, sunlight falls at a steep angle and shines most intensely on Earth’s surface.

17. Unit 2 Key Concepts At the beginning of winter, sunlight falls at a shallow angle and shines least intensely on Earth’s surface.

18. Unit 2 Key Concepts Earth’s tilt causes sunlight to strike the ground at steeper angles in summer and shallower angles in winter.

19. Unit 2 Summary The seasons are not caused by variations in Earth’s distance from the Sun. Earth’s spin axis remains tilted toward Polaris as it orbits the Sun.

20. Unit 2 Summary Earth’s tilt does not significantly change its distance from the Sun. Seasons are caused by Earth’s tilt, which affects the intensity of sunlight and the number of daylight hours at different locations on Earth.

21. Unit 2 Key Concepts

22. The Seasons