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4.2 Earth’s Rotation. DAHS Mr. Sweet. Objectives. Give evidence of Earth’s rotation. Relate Earth’s rotation to the day-night cycle and the time zones. Evidence for Rotation. Jean Foucault in 1851 Pendulum Direction of swing does not change Shifts 11 o per hour in clockwise motion
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4.2 Earth’s Rotation DAHS Mr. Sweet
Objectives • Give evidence of Earth’s rotation. • Relate Earth’s rotation to the day-night cycle and the time zones.
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
Evidence for Rotation • Coriolis Effect • Wind and water is deflected due to spin of earth • Right in North and Left in South
Evidence for Rotation • Change from day to night.
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
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
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
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
Prime Meridian • Arbitrary line in Greenwich, England • East of the PM clocks are set earlier • West of the PM clocks are set later
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
Section Review 4.2 • Page 78 • Complete questions 1, 2, 3, 4, 5