Movements of Earth Ch 26:2 Page 667-675

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

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

Evidence of Revolution Constellations change throughout the year

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

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

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

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

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

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

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

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

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