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What are Earth`s patterns?
April 2013 CH7Lesson3
Earth is always moving. One way Earth moves is that it spins around its axis. Earth`s axis is an imaginary line that runs between the North Pole and the South Pole.
How Earth moves
The axis is not straight up and down. It is tilted.
Earth turns in a counterclockwise direction at the North Pole.
This direction is opposite to the direction in which the hands of a clock move. Earth also turns from west to east.
Counterclockwise direction
Day and Night
Earth`s spinning causes day and night.Earth makes one complete spin on its axis, or rotation, every 24 hours.
During this time, half of Earth faces the sun. That half of Earth has day. The half of Earth that is not facing the sun has night.
As Earth spins, or rotates, a different part of Earth turns to face the sun.
Earth`s spinning also causes changes in the sun`s position in the sky. These changes follow a pattern.
In the morning, the sun appears to rise in the east. During the day, the sun seems to move across the sky and then set in the west. You might think the sun moves around Earth. But the sun only appears to move across the sky. Actually Earth in moving.
When it is still nighttime in Honolulu, Hawaii, the sun is raising in Seattle. In new Orleans, it is daytime and some students are already starting their school day.
Revolution Around the Sun
Earth makes one revolution when it makes one complete trip around the sun. One revolution takes about one year.
As Earth revolves around the sun, Earth's tilted axis always points in the same direction in space.
direct solar rays
Earth`s northern half is tilted toward
the sun.
Earth`s northern half is tilted away from the sun.
Seasons
A year is divided into four seasons-spring, summer, fall, and winter. The seasons are caused by:
the tilt of Earth`s axis. the planet`s revolution around
the sun. .
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As Earth moves around the sun, different parts of the planet tilt toward the sun.
-The northern half of Earth is tilted toward the sun. -It receives more direct rays of sunlight than the southern half and heats up more. Summer in the northern half. winter in the southern half.
Earth in June
-The northern half of Earth is tilted away from the sun.-It gets less sunlight and has colder temperatures than the southern half. winter in the northern half. Summer in the southern half.
Earth in December
- Neither end of Earth`s axis points toward the sun. -Both halves of Earth get about
the same amounts of sunlight.
Earth in March and September
Shadows During the Day
-A shadow forms when an object blocks the light that hits it.-The shadow has about the same shape as the object that blocks the light.
The length and direction of shadows change during the day.
morning midday afternoon
The morning shadow is long. The shadow stretches in the opposite direction from the sun in the eastern sky.
As the sun appears to move higher in the sky, the shadow becomes shorter. Around midday the sun is at its highest point in the sky.The shadow is very short.
As the sun continues moving across the sky, the shadow becomes longer.The afternoon shadow stretches in a different direction. As the sun moves toward the horizon in the west, the shadow stretches toward the east.
Shadow Length During the Year
The length of a shadow changes during the year. In the northern half of Earth,
the sun is higher in the sky in summer. the sun in lower in the sky in winter.
east
southnorth
west
winter
