The Earth in the Solar System

The Earth is a sphere. It has 3 parts:

•The atmosphere•The hydrosphere•The lithosphere

The atmosphere • The atmosphere is the air that surrounds the Earth.• Air is a mixture of gases and it is essential for life.• The atmosphere protects living things from the Sun’s

rays.

The hydrosphere • The hydrosphere is the water of the Earth. • Salt water in seas and oceans.• Fresh water in rivers, lakes and the ice that covers the

North and South Poles.

The lithosphere• The lithosphere is made up of rocks and minerals.• Part of the lithosphere is above sea level and forms

the continents and islands.• The rest is under the oceans and forms the ocean

floor.

We can represent the Earth as a small sphere, called a globe or in a flat form, called a map. Both show the continents and the oceans.

A globe is a more realistic representation because, like the Earth, it is a sphere.

A world map shows all the continents and oceans of the Earth, but it makes the Earth look flat.

The Earth’s axis is an imaginary line that goes from the North Pole to the South Pole and passes through the centre of the Earth. The Equator is an imaginary line that goes round the middle of the Earth.• The Earth’s axis passes from pole to pole through the

centre.• The Equator divides the Earth into 2 hemispheres. We

live in the Northern Hemisphere.

The Earth is the universe. The universe is enormous and has many stars, planets and satellites. The Earth is in a part of the universe called a solar system. The Sun, the planets and their satellites make up our solar system.

The Sun is a star. A star is a mass of gas that gives out heat and light.

The satellites revolve around the planets.

The Solar System: The planets in our solar system all revolve around the Sun. There are eight planets: Mercury (1), Venus (2), the Earth (3), Mars (4), Jupiter (5), Saturn (6), Uranus (7) and Neptune (8).

Our planet moves in 2 ways: rotation and revolution.• Rotation is the movement of the Earth around its axis.

The Earth takes 24 hours or 1 day to make one complete rotation. This movement causes day and night.• Revolution is the movement of the Earth around the

Sun. The Earth takes 365 days or 1 year to make one complete revolution.

The Moon is the only satellite of the Earth. It moves in 2 ways: rotation on its axis and revolution around the Earth. The Moon is lit up by the Sun. It is a sphere, but from the Earth it looks like different shapes. These shapes are called phases.

• 1. New moon. We see none of the lit side.• 2. Waxing moon. We see more and more of the lit side.• 3. Full moon. We see all of the lit side.• 4. Waning moon. We see less and less of the lit side.