EARTH

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EARTHS ROTATION

• CHAPTER 4.2

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Objectives

• Give evidence of Earths rotation.
• Relate Earths rotation to the day-night cycle
  and the time zones.

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LIKE US TODAY, EARLY OBSERVERS , WATHCHED THE
SUNRISE IN THE EAST
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AND SET IN THE WEST
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EVIDENCE FOR ROTATION

• PENDULUM, 1851 JEAN FOCAULT NO FORCE ON SWING,
• NO DIRECTIONAL CHANGE EARTH TURNING BENEATH
  PENDULUM
• CORIOLIS EFFECT WIND DIRECTIONAL CHANGE

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EVIDENCE FOR ROTATION

• CORIOLIS EFFECT WIND DIRECTIONAL CHANGE
• RIGHT IN THE NORTH
• AND LEFT IN SOUTH

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Examine evidence of Earth turning about an axis
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AXIS AND RATE OF ROTATION

• ROTATION COUNTERCLOCKWISE SPIN OF THE EARTH
  ABOUT ITS AXIS.
• TILTED 23.50 FROM PERPENDICULAR
• 1 ROTATION 24 HR 1 DAY
• 3600 / 24HR 150 PER HOUR
• 10 / 4 MIN

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AXIS
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RATE OF ROTATION

• LOCATION CIRCUMFERENCE ROTATIONAL
  RATE
• POLES 0 MILES 0 MI/HR
• 420 NORTH 18,720 MI 780 MI/HR
• EQUATOR 24,044 MI 1002 MI/HR
  

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EFFECTS OF ROTATION

• Day and Night Video

• DAILY CHANGE DAY TO NIGHT
• SUN APPEARS TO RISE IN EAST AND SET IN WEST
• PENDULUM AND CORIOLIS

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MEASURING TIME

• USED THE SUN
• RISE IN EAST SET IN WEST
• EARTH ROTATES COUNTERCLOCKWISE WHEN VIEWED FROM
  ABOVE NORTHPOLE
• SUN MOVES IN AN ARC IN THE SKY
• 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 750 W AND DUBOIS 780 W

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ALTITUDE OF SUN
SOLAR NOON
EAST
WEST
HORIZON
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Explore a model of Earth's daily rotation.
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STANDARD TIME ZONES

• TIME MERIDIAN EACH 150 FROM THE PRIME MERIDIAN.
  CENTER LINE OF A TIME MERIDIAN 7 1/2O.
• EACH TIME MERIDIAN (150) IS 1 HR DIFFERENCE IN
  TIME
• EARTH ROTATES 3600 IN 24 HRS 3600/ 24 HOURS 150
  PER HOUR THEREFORE EACH TIME ZONE IS 150 OF
  LONGITUDE

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RULES FOR TIME ZONES EAST ADD TIME WEST
SUBTRACT TIME
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US TIME ZONES

• EASTERN (750 W)
• CENTRAL (900 W) -1
• MOUNTAIN (1050 W) -2
• PACIFIC (1200 W) 3

iF THE TIME IN DUBOIS IS 100 PM, WHAT IS THE
TIME IN LA, DETROIT AND DENVER?
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INTERNATIONAL DATELINE

• IDL 1800 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
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Traveling Across Time Zones