Earth’s Rotation

The apparent motion of the Sun in the sky is

caused by the rotation of Earth on its axis.

Earth makes one complete rotation, in a west-to-

east direction, once each day (every 24h).

While Earth spins on its

axis, it also revolves, or

travels around the Sun.

Earth’s orbit is

elliptical and it takes approximately 365.25

days (1 year) to make

one complete

revolution around the Sun. This is known as

its orbital period.

The Moon also rotates on its axis while it

revolves around the Earth.

The Moon completes one rotation on its

axis in about the same time it takes to

complete one revolution around Earth.

What keeps the

planets orbiting the

Sun, and the Moon

orbiting Earth?

The answer is

gravitational force,

or the force of

attraction between

all masses in the Universe.

A geocentric model of the

Solar System which

describes the Earth as the centre of the system and

the Sun and other planets

revolve around it.

A heliocentric model of

the Solar System which

describes the Sun as the centre of the system and

the Earth and other

planets revolve around it.

Earth’s rotational axis

is tilted 23.5o from the

vertical plane.

This tilt affects the average daytime

temperature

experienced by

Earth’s hemisphere’s.

As Earth revolves around the Sun, the northern and southern hemispheres experience the seasons – spring, summer, autumn, and winter.

When Earth is farthest from the Sun, the northern hemisphere is tilted toward the Sun, causing intense heating of the Earth’s surface and atmosphere.

When Earth is closest to the Sun, the northern hemisphere is tilted away from the Sun, causing less heating of the Earth’s surface and atmosphere.

Solstices, an event where the tilt of the

Earth’s axis is the most inclined toward

or away from the Sun, occur twice

each year.

Equinoxes are the two times during

the year when the hours of daylight

equal the hours of darkness.

There are eight phases of the Moon which

occur over a lunar cycle.

An eclipse is a darkening of a celestial

object due to the position of another

celestial object.

A solar eclipse occurs when the moon is

aligned between Earth and the Sun,

blocking the Sun from being observed.

A lunar eclipse occurs when Earth is

positioned between the Sun and the Moon, casting a shadow on the Moon.

Tides are the rising and falling of the surface of

oceans, and are caused by the gravitational

pull of the Moon and, to a lesser extent, the

Sun.

The Moon’s gravitational force pulls Earth and

its oceans towards it.