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# THE GLOBE - PowerPoint PPT Presentation

THE GLOBE. THE EARTHS ROTATION ON ITS AXIS – DAY AND NIGHT.

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THE EARTHS ROTATION ON ITS AXIS – DAY AND NIGHT

• Earth’s axis is the imaginary line that passes between the north and south poles. Earth spins or rotates on its axis. We cannot feel earth rotating because it is so big. Because Earth is round, the sun’s rays can only shine on one side of earth at the same time.The round shape means that one half of the world experiences night while the other half experiences day.

• Earth takes 24 hours to complete one rotation.

• As earth rotates, different parts of the earth’s surface move in and out of the sun’s rays

• Earth’s rotation is the cause of day and night.

• Earth rotates from west to east.

SUN RAYS

EARTH

EARTH’s AXIS

ANGLE OF AXIS

• Earth’s axis tilts at 23½ degrees away from perpendicular. This means that certain times of the year different parts of Earth tilt towards or away from the sun. The tilt of Earth’s axis affects the length of day and night and is responsible for the seasons

• Earth revolves around the sun. It takes 365¼ days for Earth to complete one revolution around the sun. Examine the diagram below to see how Earth’s revolution and the tilt of Earth’s axis result in seasons in different parts of the world.

EQUINOX, SOLSTICE AND THECHANGE IN ANGLE OF THE MIDDAY SUN

Equinox

• Equinox means equal night. The equinoxes are on an exact date when the lenght of day and night is the same number of hours long.

• The equinoxes occur on 21 March and 23 September.

• At these times of the year the angle of Earth’s axis titls neither towards the sun nor away from the sun. The sun is directly above the equator during the equinoxes.

• The equinoxes are associated with the spring and autumn seasons.

• The sun reaches its highest point in the sky at noon. The height of the sun in the sky depends on where Earth is in relation to the sun. The sun reaches its highest point in the sky for places in the northen hemisphere on 21 June and on 21 December for places in the southern hemisphere. At the equinoxes, the sun is directly above the equator. This means the angle of the sun is 90 degrees/perpendicular to Earth.

21 MARCH

WINTER in SOUTHER HEMISPHERE

SPRING in NORTHERN HEMPISPHERE

23 SEPTEMBER

SPRING in SOUTHERN HEMPISPHERE

WINTER in NORTHERN HEMISPHERE

EQUINOX, SOLSTICE AND THECHANGE IN ANGLE OF THE MIDDAY SUN

Solstice

• The solstice are the dates of the year when one hemisphere has the longest number of hours of daylight and the opposite hemsiphere has the shortest number of hours of daylight.

• Solstices occur in 21 December and on 21 June

• On 21 June, the sun is directly above the Tropic of Cancer.

• On 21 December, the sun is directly above the Tropic of Capricorn.

• The solstices are associated with the summer and winter seasons.

21 JUNE

WINTER in SOUTHERN HEMISPHERE

SUMMER in NORTHERN HEMISPEHRE

21 DECEMBER

SUMMER in SOUTHERN HEMISPEHRE

WINTER in NORTHERN HEMISPHERE