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
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. Solstices and Equinoxes (p.289)

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