THE MOVEMENTS OF THE MOVEMENTS OF THE EARTH AND ITS THE EARTH AND ITS

EFFECTSEFFECTS

The movements of the EarthThe movements of the Earth

The Earth moves in The Earth moves in two different ways:two different ways:• RotationRotation. . • RevolutionRevolution. .

RotationRotation

The Earth rotates The Earth rotates (spins) on its own (spins) on its own axis.axis.

RotationRotation

Its axis is an Its axis is an imaginary line imaginary line between the North between the North Pole and the South Pole and the South Pole.Pole.

The axis is tilted.The axis is tilted.

RotationRotation

The Earth takes 24 The Earth takes 24 hours to complete hours to complete a full circle = a a full circle = a day.day.

The Earth’s axis The Earth’s axis is not is not perpendicular to perpendicular to the plane of the the plane of the Earth’s orbit. Earth’s orbit.

The axis is tilted The axis is tilted 23.5º with 23.5º with respect to the respect to the plane of plane of movement movement around the Sun.around the Sun.

The consequences of The consequences of rotationrotation

The rotation of the The rotation of the Earth every 24 Earth every 24 hours causes day hours causes day and night.and night.

• It is day on the It is day on the side of Earth side of Earth where the sun where the sun shines.shines.

• On the other side On the other side of Earth is night.of Earth is night.

The consequences of The consequences of rotationrotation

Rotation, seen from North Pole, is Rotation, seen from North Pole, is anticlockwise (from west to east) . anticlockwise (from west to east) .

So the Sun rises in the east. So the Sun rises in the east.

Sunset: when the Sun disappears at the Sunset: when the Sun disappears at the end of the day.end of the day.

Sunrise: when the sun first appears in the Sunrise: when the sun first appears in the morningmorning

RevolutionRevolution

The Earth revolves around the Sun.The Earth revolves around the Sun.

The Earth takes 365 ¼ days to complete The Earth takes 365 ¼ days to complete the revolution = a year.the revolution = a year.

The consequences of The consequences of revolution: the seasonsrevolution: the seasons

Three factors cause the seasons:Three factors cause the seasons:• The revolution of the Earth around the SunThe revolution of the Earth around the Sun• The tilt of the Earth’s axis of rotation The tilt of the Earth’s axis of rotation

respects to the Plane of the Ecliptic.respects to the Plane of the Ecliptic.• The tilt of the Earth’s axis remains constant.The tilt of the Earth’s axis remains constant.

The tilt of the axis causes:The tilt of the axis causes:

Differences in temperatureDifferences in temperatureDifferences in the duration of day and Differences in the duration of day and

night.night.

Revolution causes:Revolution causes:- The four characteristic positions of the - The four characteristic positions of the

Earth (summer and winter Earth (summer and winter solsticessolstices and and spring and autumn spring and autumn equinoxesequinoxes)..

- The - The seasonsseasons of the year of the year

Solsticies and equinoxesSolsticies and equinoxes

Solstice: one of two days in the year when Solstice: one of two days in the year when the Sun is at its highest or lowest point in the Sun is at its highest or lowest point in the sky at noon (12 pm)the sky at noon (12 pm)

Solsticies and equinoxesSolsticies and equinoxes

Equinox: one of two days in the year when Equinox: one of two days in the year when day and night are the same length of time.day and night are the same length of time.

The SeasonsThe Seasons

The Sun is not at The Sun is not at the exact centre of the exact centre of the Earth’s orbit the Earth’s orbit and the Earth’s and the Earth’s orbit around the orbit around the Sun is not a perfect Sun is not a perfect circle.circle. So, the distance So, the distance of the Earth from of the Earth from the Sun varies as the Sun varies as the Earth revolves the Earth revolves around the Sun. around the Sun.

The seasons in the Northern The seasons in the Northern HemisphereHemisphere

During the summer in the northern hemisphere, the Earth is During the summer in the northern hemisphere, the Earth is

farther away from the Sun. The temperature is higher farther away from the Sun. The temperature is higher because there are more hours of daylight and because the because there are more hours of daylight and because the Sun’s rays hit the Earth’s surface at an angle of 90º.Sun’s rays hit the Earth’s surface at an angle of 90º.

During the seasons, temperature changes During the seasons, temperature changes depend on angle at which the Sun’s rays depend on angle at which the Sun’s rays hit the Earth.hit the Earth.

The seasons are caused by:The seasons are caused by:

The movement of the Earth around The movement of the Earth around the Sun.the Sun.

The tilt of the Earth’s axis of rotation.The tilt of the Earth’s axis of rotation. The fact that the tilt remains The fact that the tilt remains

constant.constant.