4.2 EARTH’S ROTATIONDAHS

Mr. Sweet

1

OBJECTIVES

Give evidence of Earth’s rotation. Relate Earth’s rotation to the day-night cycle

and the time zones.

2

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

4

EVIDENCE FOR ROTATION

Change from day to night.

5

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

6

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

7

Measuring Time

Earth rotates clockwise

Half of earth is light and half dark

24 hour day Solar noon is when

sun is directly overhead Moves westward 15o

every day or 1o every 4 minutes

8

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

9

U.S. TIME ZONES

10

WORLD TIME ZONES

11

PRIME MERIDIAN

Arbitrary line in Greenwich, England

East of the PM clocks are set earlier

West of the PM clocks are set later

12

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 day ahead of the eastern half USA is one day

behind Eastern Asia 13

SECTION REVIEW 4.2

Page 78 Complete questions 1, 2, 3, 4, 5

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