1. Movements of Earth
Ch 26:2
Page

2. Two movements 1. Rotation--Earth spins on its axis Day/night Evidence
Foucault’s pendulum
Coriolis effect
—the path of the swinging pendulum seems to change but it doesn’t, the Earth spins beneath it

3. 2. Revolution--Earth moves around the sun
Speed is 29.8km/s
Earth’s orbit is an ellipse
The closest point is perihelion
The farthest point is aphelion

4. Evidence of Revolution
Constellations change throughout the year

5. Measuring Time Day based on rotation Year based on revolution
Month based on a lunar cycle

6. Calendars Many civilizations invented calendars Egyptian-solar year
Babylonians-12 month lunar year
Aztecs

7. Modern Calendar
365 ¼ days in a year
Leap year every 4 years

8. Time Zones The sun is used as the basis of time
Noon is when the sun is directly overhead
Because earth rotates that time is different
So, the earth is divided into 24 time zones
360° in a circle divided by 24 = 15° per time zone

9. International Date Line
24 time zones and 24 hours in the day
The day must change somewhere
The international date line run north to south through the Pacific Ocean

10. Seasons Earth has a 23 ½ ° tilt on its axis
This tilt causes seasons as Earth revolves around the sun
The difference in seasons is because of how directly the sun’s rays hit the surface of the Earth

11. Daylight Savings Time
In temperate areas, there is more daylight in the summer than in the winter
In April, clocks are set forward to have more hours of daylight in the evening
It is an energy saving measure

12. Equinoxes Equinox means equal night
Vernal equinox—spring March 21 or 22
Autumnal equinox—fall September 22 or 23

13. Time is divided based on Earth's movement
Day -- one rotation
Year -- one revolution
Time Zones
International Date Lines