Earth’s Place in Space

1. Chapter 10 Earth’s Place in Space

2. Earth’s Shape • Spherical • Shaped like a ball

3. Evidence of Earth’s Shape • Horizon • Boat coming over horizon (you see the top first) • Shadow • Curved shadow during lunar eclipse • Gravity • Gravity attracts particles toward center • Pictures • Pictures from space

4. Not Quite a Perfect Sphere… • Slight bulge at equator due to spinning (centrifugal force)

5. What is a “Day”? • Rotation • Time it takes for Earth to rotate one complete turn = 1 day • Each Rotation is one day (24 hours) • Why Sun (and moon/stars) rises and sets

6. What is a “Year”? • Revolution (orbit) • Each Revolution is one year

7. Why does Earth orbit the Sun? • Gravity • The sun’s gravitational pull holds the Earth in orbit • Gravitational pull depends on the masses of the objects and the distance between them • Earth’s orbit around the Sun is nearly circular • Ellipse (with Sun at one focus)

8. How does the Sun give us energy? • Fusion – In the Sun’s core, there is so much heat and pressure that the nuclei of atoms combine. This process releases LARGE amounts of energy. • Core temperature = 15,000,000 °C • Surface temperature = 5,500 °C • Light & Thermal Energy – Some of the Sun’s energy reaches us on Earth as light and heat.

9. What Causes the Seasons? • Earth’s Tilt (23.5⁰) • More Direct Sunlight • Summer • Longer Days • Less Direct Sunlight • Winter • Shorter Days

10. Solstices and Equinoxes • Solstice • Summer - Sun reaches far point North of Equator • Tropic of Cancer • Longest Day • Winter – Sun reaches far point South of Equator • Tropic of Capricorn • Shortest Day • Equinox • Sun Directly above Equator • Spring and Fall

11. SolsticesandEquinoxes (p.289)

12. Earth’s Seasons Indirect Sunlight Direct Sunlight Shorter Days Longer Days