#### Transcript 4.2 Earth`s Rotation

4.2 EARTH’S ROTATION
1
DAHS
Mr. Sweet
OBJECTIVES
Give evidence of Earth’s rotation.
 Relate Earth’s rotation to the day-night cycle and
the time zones.

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Evidence for Rotation

Jean Foucault in 1851
Pendulum
 Direction of swing
does not change
 Shifts 11o per hour in
clockwise motion
 Earth is turning
beneath the pendulum

3
EVIDENCE FOR ROTATION

Coriolis Effect
Wind and water is
deflected due to spin of
earth
 Right in North and
Left in South

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EVIDENCE FOR ROTATION

Change from day to
night.
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Axis
Imaginary line from
pole to pole
 Orbital Plane


Earth’s path around
the sun
Axis tilted to 23.5o
 Pointed at Polaris
Star


Called Parallelism
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Rate of Rotation
360o every 23 hours,
56 minutes, 4.1
seconds
 15o every hour
 Distance traveled at


Equator is 40,074 km


1690 km per hour
Poles is 0 km
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Measuring Time
Earth rotates
clockwise
 Half of earth is light
and half dark
 24 hour day
 Solar noon is when
sun is directly


Moves westward 15o
every day or 1o every 4
minutes
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STANDARD TIME ZONES
24 time zones
 Each 15o of longitude wide
 Each time zone centered on a line of longitude
called a time meridian

All area in the time zone keep the same time
 Clock time is the average solar time at the zone’s
time meridian


Rarely a straight line on land
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U.S. TIME ZONES
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WORLD TIME ZONES
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PRIME MERIDIAN
Arbitrary line in
Greenwich, England
 East of the PM clocks
are set earlier
 West of the PM clocks
are set later

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INTERNATIONAL DATE LINE
The longitude at
which the date
changes
 Moving west the date
is one day later
 Moving east the date
is one earlier
 Western half is one