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# The movements of the Earth

## on Feb 27, 2012

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## The movements of the Earth Presentation Transcript

• THE MOVEMENTS OF THE EARTH AND ITS EFFECTS
• The movements of the Earth
• The Earth moves in two different ways:
• Rotation .
• Revolution .
• Rotation
• The Earth rotates (spins) on its own axis.
• Rotation
• Its axis is an imaginary line between the North Pole and the South Pole.
• The axis is tilted.
• Rotation
• The Earth takes 24 hours to complete a full circle = a day.
• The Earth’s axis is not perpendicular to the plane of the Earth’s orbit.
• The axis is tilted 23.5º with respect to the plane of movement around the Sun.
• The consequences of rotation
• The rotation of the Earth every 24 hours causes day and night.
• It is day on the side of Earth where the sun shines.
• On the other side of Earth is night.
• The consequences of rotation
• Rotation, seen from North Pole, is anticlockwise (from west to east) .
• So the Sun rises in the east.
• Sunset: when the Sun disappears at the end of the day.
• Sunrise: when the sun first appears in the morning
• Revolution
• The Earth revolves around the Sun.
• The Earth takes 365 ¼ days to complete the revolution = a year.
• The consequences of revolution: the seasons
• Three factors cause the seasons:
• The revolution of the Earth around the Sun
• The tilt of the Earth’s axis of rotation respects to the Plane of the Ecliptic.
• The tilt of the Earth’s axis remains constant.
• The tilt of the axis causes: Differences in temperature Differences in the duration of day and night.
• Revolution causes: - The four characteristic positions of the Earth (summer and winter solstices and spring and autumn equinoxes ) . - The seasons of the year
• Solsticies and equinoxes
• Solstice: one of two days in the year when the Sun is at its highest or lowest point in the sky at noon (12 pm)
• Solsticies and equinoxes
• Equinox: one of two days in the year when day and night are the same length of time.
• The Seasons
• The Sun is not at the exact centre of the Earth’s orbit and the Earth’s orbit around the Sun is not a perfect circle.
• So, the distance of the Earth from the Sun varies as the Earth revolves around the Sun.
• The seasons in the Northern Hemisphere
• During the summer in the northern hemisphere, the Earth is farther away from the Sun. The temperature is higher because there are more hours of daylight and because the Sun’s rays hit the Earth’s surface at an angle of 90º.
• During the seasons, temperature changes depend on angle at which the Sun’s rays hit the Earth.
•
• The seasons are caused by:
• The movement of the Earth around the Sun.
• The tilt of the Earth’s axis of rotation.
• The fact that the tilt remains constant.