4.2 E ARTH ’ S R OTATION DAHS Mr. Sweet 1

O BJECTIVES 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 11 o per hour in clockwise motion Earth is turning beneath the pendulum 3

E VIDENCE FOR R OTATION Coriolis Effect Wind and water is deflected due to spin of earth Right in North and Left in South 4

E VIDENCE FOR R OTATION Change from day to night. 5

Axis Imaginary line from pole to pole Orbital Plane Earth’s path around the sun Axis tilted to 23.5 o Pointed at Polaris Star Called Parallelism 6

Rate of Rotation 360 o every 23 hours, 56 minutes, 4.1 seconds 15 o 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 15 o every day or 1 o every 4 minutes 8

S TANDARD T IME Z ONES 24 time zones Each 15 o 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. T IME Z ONES 10

W ORLD T IME Z ONES 11

P RIME M ERIDIAN Arbitrary line in Greenwich, England East of the PM clocks are set earlier West of the PM clocks are set later 12

I NTERNATIONAL DATE L INE 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

S ECTION R EVIEW 4.2 Page 78 Complete questions 1, 2, 3, 4, 5 14