Chapter 5 Lesson 2 Earth and the Sun

1. Chapter 5 Lesson 2Earth and the Sun Pages C18 – C26

2. How Do We Know Earth is Rotating? • The sun seems to move across the sky because the Earth is rotating, or spinning. • The Earth rotates on its axis. • The axis is an imaginary line through the Earth from the North to the South pole.

3. How Do We Know Earth is Rotating? • Earth makes one rotation when it makes one complete spin on its axis. • It takes 24 hours for the Earth to make one rotation. • What happens as a result of this motion? • Earth experiences day and night!

4. Data That Shows the Earth is Spinning • Satellites can observe the rotation of the Earth from space. • Foucault’s Pendulum: http://app.discoveryeducation.com/player/view/assetGuid/7E87B9CD-0007-4779-970F-8E8FDEB2F8B8 • Proved that the Earth moved beneath the pendulum, so it must be rotating.

5. Data That Shows the Earth is Spinning • The shape of the Earth isn’t a perfect sphere. • Earth is slightly flattened at the poles and is slightly wider at the equator because the Earth spins quickly.

6. Data That Shows the Earth is Spinning • The Sun’s position in the sky changes throughout the day. • Different locations on Earth receive different amounts of sunlight and darkness throughout the Earth’s 24 hour rotation.

7. The Sun’s Path in the Sky • The sun rises in the east and rises higher in the sky as the day passes. • At midday (noon), the sun is at its highest point in the sky. • After midday, the sun begins to set in the west.

8. What are Standard Time Zones? • Because the sun hits the Earth in different positions, it also hits the Earth at different times. • A standard time zone is a belt 15o wide in which all places have the same time. • There is a one-hour time difference between time zones that are next to each other.

9. What are Standard Time Zones? • If you travel west, you turn your clock back (subtract) one hour. • If you travel east, you turn your clock ahead (add) one hour.

10. International Date Line • The International Date Line is the location where a new day begins. • The International Date Line is located at 180o longitude. • If you cross this date line going West, you add 1 day.

11. Why Are There Seasons? • The change in seasons is not caused by the change in distance between the Earth and the Sun. • One complete trip around the sun is called a revolution. • It takes the Earth 365 days to complete 1 revolution around the Sun.

12. Why Are There Seasons? • While the Earth is revolving around the Sun, it is also rotating on its axis. • The Earth’s tilt on its axis as it revolves around the Sun causes the change in seasons.

13. Why Are There Seasons? • When the Northern Hemisphere is tilted towards the Sun, the sun’s rays strike the Northern Hemisphere at high angles. • This causes the Northern Hemisphere to have summer.

14. Why Are There Seasons? • When the Northern Hemisphere is tilted away from the Sun 6 months later, the rays from the Sun are slanted at low angles • This causes the Northern Hemisphere to be in winter.

15. Try it on Your Own!

16. Where is the Sun in Summer and in Winter? • The steeper the angle of the Sun’s rays, the higher in the sky the Sun will appear. • This means the Sun appears highest in the sky in the summer and lowest in the sky in the winter. • In spring and fall, the Sun is somewhere in between.

17. How is the Sun an Important Energy Source? • The Sun is the energy source for life on Earth. • Light from the Sun is necessary for the growth of living organisms (plants and animals). • Fossil fuels (coal, oil, natural gas) were formed from the decay of ancient organisms. • The energy we use to power our cars and homes runs on energy from the Sun that was trapped billions of years ago!

18. How is the Sun an Important Energy Source? • The Sun provides energy for many natural events. • The Sun is the source of energy for the water cycle. The Sun causes the water to evaporate, which creates clouds and precipitation. • The Sun’s energy also creates winds and ocean currents.