Download Movements of Earth

Movements of Earth
Ch 26:2
Page 667-675
Two movements
1. Rotation--Earth
spins on its axis

—the
path of the swinging pendulum
seems to change but it doesn’t, the
Earth spins beneath it
Day/night
Evidence
 Foucault’s pendulum
 Coriolis effect
2. Revolution--Earth moves around the sun
Speed is 29.8km/s
Earth’s orbit is an
ellipse
The closest point is
perihelion
The farthest point is
aphelion
Evidence of Revolution
 Constellations
change
throughout the
year
Measuring Time

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
Day based on rotation
Year based on revolution
Month based on a lunar cycle
Calendars

Many civilizations
invented calendars

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Egyptian-solar year
Babylonians-12
month lunar year
Aztecs
Modern Calendar


365 ¼ days in a year
Leap year every 4 years
Time Zones

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The sun is used as the basis of time
Noon is when the sun is directly overhead
Because earth rotates that time is different
So, the earth is divided into 24 time zones
360° in a circle divided by 24 = 15° per time
zone
International Date Line

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
24 time zones and
24 hours in the day
The day must
change somewhere
The international
date line run north
to south through the
Pacific Ocean
Seasons



Earth has a 23 ½ ° tilt
on its axis
This tilt causes
seasons as Earth
revolves around the
sun
The difference in
seasons is because of
how directly the sun’s
rays hit the surface of
the Earth
Daylight Savings Time

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In temperate areas, there is more daylight
in the summer than in the winter
In April, clocks are set forward to have
more hours of daylight in the evening
It is an energy saving measure
Equinoxes

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Equinox means equal night
Vernal equinox—spring March 21 or 22
Autumnal equinox—fall September 22 or 23
Time is divided based on Earth's movement

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Day -- one rotation
Year -- one revolution
Time Zones
International Date Lines