Here we focus on those scientific concepts that are the hardest to explain to children. We break it down into what pupils need to know and outline the background science. Even though much of the background science does not need to be taught to primary aged children, it is useful for you as a teacher when addressing misconceptions and children’s challenging questions. 

Please refer to your national curriculum documents when planning your sequence of work and ensure that you teach the correct knowledge for your year group. 

What do children need to know about Earth and space? 

Your pupils’ learning about Earth and space connects to their understanding of seasonal changes, light and shadow and forces. Children’s misconceptions are common with this topic because of the tricky nature of some of the scientific concepts, so it is important to be secure in your understanding of the background science before you teach it. We have included some ideas for how to teach Earth and space in part two of this topic guide. 

Key scientific concepts: Pupils need to... 

1. Know that the Sun is the centre of our solar system and the other planets (including Earth) orbit around it

2. Be able to describe how the Moon moves in relation to Earth

3. Know how the Earth’s rotation causes day and night

1. The sun is the centre of the solar system

Pupils need to know: 

• The Sun is the centre of our solar system and is orbited by 8 planets, including Earth

• How to use models to illustrate the relative size and scale of the solar system

• Our understanding of the solar system has developed over time

Background science

Our solar system is part of the Milky Way galaxy, which is just one of millions of galaxies that make up the Universe. The Sun is a star at the centre of our solar system with all other objects orbiting around it, including eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune). 

The Sun:

• Is by far the biggest object in the solar system, counting for over 99% of the solar system’s total mass 

• Its mass gives it a huge gravitational pull causing the other planets to remain in orbit around it

• The planets’ orbits are fixed and elliptical in shape. The closer they are to the Sun, the quicker they travel and they all travel in an anticlockwise direction. Most of the planets are orbited by moons, which are also known as natural ‘satellites’ 

In terms of relative size and scale, the Earth is 93 million miles from the Sun and has a volume approximately one millionth that of the Sun. So, if the Sun was the size of a football (22cm diameter), the Earth would be a sphere with a 2mm diameter and be 23 metres away. Take a look at this video on BBC Bitesize which illustrates this. 

We haven’t always pictured the solar system as we do now, however, with scientific models changing significantly over time. In the 2nd century, Ptolemy of Alexandria developed the geocentric (Earth-centered) model of the solar system, which placed Earth at the centre. This view dominated scientific thought until the 16th century when Nicolaus Copernicus developed the heliocentric (Sun-centered) model, which placed the Sun at the centre.

2. The Moon orbits the Earth

Pupils need to know: 

• The Moon is a natural satellite that orbits Earth

• Its gravitational pull is important for the stability of Earth’s orbit and life on Earth

• Its orbit is around 27-28 days, and this is used for creating the lunar calendar

Background science

The Moon: 

• Is a natural satellite made of rock and metal (like Earth, Mercury, Venus and Mars) and is covered in craters and mountains 

• Is approximately a quarter the size of Earth, which means its gravitational pull is weaker – about one-sixth of Earth’s gravity. This is why astronauts who have landed on the Moon’s surface weigh less (but of course their mass is unchanged) and can jump much higher

• Is important for maintaining life on Earth. Its gravitational pull improves the stability of the Earth’s orbit, which means we have a more settled climate. It is also the cause of our tides, as the Moon’s gravity (along with the Sun’s) pulls the water in our oceans across the Earth

• Its orbit around the Earth is elliptical and takes 27.3 days to complete. As it orbits, it also rotates on its own axis (just like Earth). It takes about the same amount of time to rotate as it does to complete its orbit, which means we appear always to be looking at the same surface of the moon and might think it is not rotating

• The moon is not a source of light and reflects light from the Sun. So, ‘moonlight’ is actually just sunlight reflecting off the Moon’s surface. We see the moon because it is illuminated by the sun

The shape of the Moon in the sky appears to change each night over a month. There are eight phases from a new moon to a full moon and it is our view of the Moon that is changing (not its shape). Our view of the illuminated part of the Moon changes each night, depending on where the Moon is in its orbit around Earth. A full view of the completely illuminated side of the Moon is known as a full moon. As it continues its orbit, we start to see less of the Moon lit by the Sun and eventually we don’t see any of the Moon illuminated. This phase is called a new moon and the side of the Moon facing Earth is dark.

3. Earth’s rotation causes day and night

Pupils need to know: 

• The Earth rotates on its own axis, which is the cause of day and night

• It takes 24 hours to complete one full rotation

• The Earth’s rotation is why it looks like the Sun is moving across the sky

Background science

As the Earth orbits the Sun, it is also rotating on its own axis. One complete rotation takes 24 hours, which is the length of one whole day and night. In the UK, when the Earth is facing the Sun it is our daytime, but the other side of the planet (e.g., in Australia) is facing away from the Sun, so it is dark and therefore nighttime.

The Sun appears to move across the sky during the day, rising in the east and setting in the west. The Sun isn’t moving but we are, due to the Earth’s rotation, which is turning from west to east.

Over a year, the length of the day (i.e., the time that the Sun is shining) changes in most parts of the world, giving us our seasons. This is because the Earth’s axis is permanently tilted so as it orbits the Sun, the two hemispheres of the Earth receive different amounts of sunlight. When the North Pole is exposed more to the Sun than the South Pole, the countries in the northern hemisphere (e.g., the UK) get more Sun and it is summer and when it is tilted away it is our winter. The reverse happens in the southern hemisphere, which is why it is summer in Australia over Christmas. At the equator there is very little change in the length of the day and night or seasonal change. For more information, take a look at the Institute of Physics ‘Explaining the seasons’.

Ideas to try with your class  

Now you've got the tricky scientific concepts under your belt, try our ideas to help you explore Earth and space with your class in a way they will understand in part two of this topic guide! 

You can also take a look at the related topic guides for light and forces. 

Image credit: Earth as seen from space by NASA Goddard Space Flight Center via Flickr CC BY 2.0