1. EARTH’S ROTATION CHAPTER 4.2

2. Objectives Give evidence of Earth’s rotation. Give evidence of Earth’s rotation. Relate Earth’s rotation to the day- night cycle and the time zones. Relate Earth’s rotation to the day- night cycle and the time zones. 2

3. LIKE US TODAY, EARLY OBSERVERS, WATHCHED THE SUNRISE IN THE EAST

4. AND SET IN THE WEST

5. EVIDENCE FOR ROTATION PENDULUM, 1851 JEAN FOCAULT NO FORCE ON SWING, PENDULUM, 1851 JEAN FOCAULT NO FORCE ON SWING, NO DIRECTIONAL CHANGE = EARTH TURNING BENEATH PENDULUM NO DIRECTIONAL CHANGE = EARTH TURNING BENEATH PENDULUMDIRECTIONAL CORIOLIS EFFECT – WIND DIRECTIONAL CHANGE CORIOLIS EFFECT – WIND DIRECTIONAL CHANGE

6. EVIDENCE FOR ROTATION CORIOLIS EFFECT – WIND DIRECTIONAL CHANGE CORIOLIS EFFECT – WIND DIRECTIONAL CHANGE RIGHT IN THE NORTH RIGHT IN THE NORTH AND LEFT IN SOUTH AND LEFT IN SOUTH

7. Examine evidence of Earth turning about an axis

9. AXIS AND RATE OF ROTATION ROTATION – COUNTERCLOCKWISE SPIN OF THE EARTH ABOUT IT’S AXIS. TILTED 23.5 0 FROM PERPENDICULAR 1 ROTATION = 24 HR = 1 DAY 360 0 / 24HR = 15 0 PER HOUR 1 0 / 4 MIN

10. AXIS

12. RATE OF ROTATION LOCATION CIRCUMFERENCE ROTATIONAL RATE POLES 0 MILES 0 MI/HR 42 0 NORTH 18,720 MI 780 MI/HR EQUATOR 24,044 MI 1002 MI/HR

13. EFFECTS OF ROTATION DAILY CHANGE DAY TO NIGHT DAILY CHANGE DAY TO NIGHT SUN APPEARS TO RISE IN EAST AND SET IN WEST SUN APPEARS TO RISE IN EAST AND SET IN WEST PENDULUM AND CORIOLIS PENDULUM AND CORIOLIS Day and Night Video Day and Night Video Day and Night Day and Night

14. MEASURING TIME USED THE SUN USED THE SUN RISE IN EAST SET IN WEST RISE IN EAST SET IN WEST EARTH ROTATES COUNTERCLOCKWISE WHEN VIEWED FROM ABOVE NORTHPOLE EARTH ROTATES COUNTERCLOCKWISE WHEN VIEWED FROM ABOVE NORTHPOLE SUN MOVES IN AN ARC IN THE SKY SUN MOVES IN AN ARC IN THE SKY HIGHEST POINT IN ARC = SOLAR NOON = SUN DIRECTLY OVERHEAD TO AN OBSERVER HIGHEST POINT IN ARC = SOLAR NOON = SUN DIRECTLY OVERHEAD TO AN OBSERVER –BECAUSE EARTH ROTATES, SOLAR NOON DOES NOT OCCUR AT THE SAME TIME DAILY –EX. PHILLY 75 0 W AND DUBOIS 78 0 W

15. ALTITUDE OF SUN HORIZON EASTWEST SOLAR NOON

16. Explore a model of Earth's daily rotation.

17. STANDARD TIME ZONES TIME MERIDIAN – EACH 15 0 FROM THE PRIME MERIDIAN. CENTER LINE OF A TIME MERIDIAN 7 1/2 O. EACH TIME MERIDIAN (15 0 ) IS 1 HR DIFFERENCE IN TIME EARTH ROTATES 360 0 IN 24 HRS 360 0 / 24 HOURS = 15 0 PER HOUR THEREFORE EACH TIME ZONE IS 15 0 OF LONGITUDE

19. The prime meridian SUNLIGHT A time meridian A standard time zone is 15° wide.

20. RULES FOR TIME ZONES EAST – ADD TIME WEST – SUBTRACT TIME

22. iF THE TIME IN DUBOIS IS 1:00 PM, WHAT IS THE TIME IN: LA, DETROIT AND DENVER? US TIME ZONES EASTERN (75 0 W) EASTERN (75 0 W) CENTRAL (90 0 W) -1 CENTRAL (90 0 W) -1 MOUNTAIN (105 0 W) -2 MOUNTAIN (105 0 W) -2 PACIFIC (120 0 W) – 3 PACIFIC (120 0 W) – 3

24. INTERNATIONAL DATELINE IDL – 180 0 MERIDIAN – –OPPOSITE THE PRIME MERIDIAN WHEN TRAVELING: – –EAST ACROSS DATELINE – SUBTRACT A DAY – –WEST ACROSS DATELINE – ADD A DAY only at midnight on the international dateline does earth have the same day! How dateline works

25. Traveling Across Time Zones