The Earth and Beyond

The Sun is the star at the centre of our solar system. Here is a useful mnemonic to help remember their order: My Very Easy Method Just Speeds Up Naming Planets.

What do we know about the Sun? The Sun is 150 million kilometres away from us. It has a diameter of 1,393,000 km. It was probably formed from a large cloud of gas about 5,000 million years ago.

The moon orbits the Earth... Sun Earth moon ...as the Earth orbits the Sun.

As the Earth orbits around the Sun, it also spins on its own axis; which is tipped.

At any time, half of the Earth faces the sun and therefore receives light. This part is in day. This part is in night. The other half faces away from the Sun, and so receives very little light.

What causes the seasons? As the Earth orbits the Sun, when its axis tips towards the Sun, the weather gets warmer. When it tips away, the weather gets colder, causing the Earth’s seasons.

Facts about Earth It is the only planet that has an atmosphere containing 21 percent oxygen. It is the only planet that has liquid water on its surface. It is the only planet in the solar system that has life. The Earth is the only inner planet (Mercury, Venus, Earth and Mars) to have one large satellite, the Moon.  Mars has two very tiny moons.  Mercury and Venus have none.

The Earth is fragile.  Its surface is split into plates (tectonic plates) which float on a rocky mantle – the layer between the surface of the earth, its crust, and its hot liquid core.  The inside of the Earth is active and earthquakes, volcanoes and mountain building takes place along the boundaries of the tectonic plates. 

The Earth takes 365¼ days to complete its orbit round the Sun The Earth takes 365¼ days to complete its orbit round the Sun.  The Earth’s year is therefore 365 days long but the ¼ days are added up and every fourth year has one extra day, on the 29th of February.  This fourth year is called a Leap Year (366 days) and is always a year which can be divided exactly by 4 – 2000, 2004, 2008, 2012, 2016.

The planets closer to the Sun, Mercury and Venus, have shorter years than the Earth.  The planets further away from the Sun have longer years; Pluto takes 249 of our years to make one orbit of the Sun.