Earth

A sequence to develop ideas about lighting the Earth

Classroom Activity for 5-11 Supporting Physics Teaching

Meeting reality: valuable experiences

The science of astronomy began with observations and it is vital to link this topic to the children can notice more or less directly for themselves. This is important because what we think happens is not always what actually happens and so careful observation often results in surprises. This is particularly true for children who, for example, have been brought up reading story books where the Moon is almost always drawn as a crescent in the night sky. Hence they can be surprised when they observe the various phases of the Moon or see the Moon in the daytime.

In the sciences we observe closely and then step back, think and ask the big questions. Why is it like that? How does that happen?

  • Making careful naked-eye observations
  • Reflecting on those observations
  • Connecting the observations back to the arrangement of the parts and the illumination of the parts
  • Beginning to get a sense of astronomical scales

A sequence for developing the idea

In this topic the main aim is to develop a model that children can use to account for:

  • Day and night
  • The apparent path of the Sun across the sky during the day
  • The movement of the Moon
  • The movement of the planets

The history of the development of human understanding in astronomy is just fascinating. The concept of the Earth being a sphere is not at all intuitive and this was a great step forward in our thinking.

Extending that to realising that the moon was also nearly spherical, with surface imperfections, and again to other planets, again represented huge strides in human understanding.

Teacher Tip: The ideas are developed in the Physics Narrative.

Here you can explore the variation in the length of daylight over the year.

How long is a day?


The Sun is hugely significant for life on Earth, but its perceived movements over the year will very likely need bringing to children attention.

The Sun is a star – a star that illuminates and warms us. The Sun is one star among very, very many. The Sun is, in practice, a huge nuclear reactor, so it does not need oxygen to burn in space – these are nuclear reactions, not chemical reactions. The warming and lighting are powered by these nuclear reactions.

Learning about the Sun


That the Earth is spherical is not an easy thing to believe, and this activity gives an opportunity to explore that idea.

Learning about the Earth


Explaining day and night requires an understanding of the relative movements of the Earth and the Sun, and the consequent changes in the illumination of the Earth. This is tricky, not easily done with diagrams, and is best acted out as in this activity.

Acting out day and night


This activity focuses on the movement of the moon, as seen from Earth.

Learning more about the moon


The focus here is on the movement of the planets, but there is plenty of opportunity for further research work that can intrigue.

Other planets in the solar system


A galaxy is a huge collection of stars. Our Sun is just one star among a hundred thousand million stars that make up the galaxy known as the Milky Way. The Milky Way is a spiral galaxy and the Sun is a star in one of the spiral arms towards the edge of the galaxy. The universe is made up of about a hundred thousand million galaxies – each of which contain about a hundred thousand million stars. This activity seeks to raise some awe and wonder about where we live.

Where we live


Messages from research and practice: specific tripwires for this idea

This topic is all about lighting and relative movement

Whilst this area of science does not lend itself to practical investigations, it is a wonderful one for making links with scientific ideas from the rest of the curriculum, particularly light. There are certain ideas the children need to understand, such as light travelling from a source. We see things around us in the daytime because the light from the Sun reflects off them into our eyes. The Sun looks like flat disc in the sky but, of course, it is a sphere. It will help children to look at a large ball on the other side of the playground to get a feel for the fact that a sphere looks like a plate or disc from a distance. The Sun looks very placid in the sky so it is useful for the children to see some internet photos that show it to be a very dynamic and explosive object.

The Sun appears to move across the sky during the day time and eventually the children will need to understand that it is not in fact the Sun moving around us but us moving around the Sun. It is therefore always best to talk about how the Sun seems to move.

Seeing what is there


Owing to light pollution, we are not as familiar with the night sky as our ancestors. In a city there is so much background light that hardly any stars can be seen at night. It is truly awesome to see the multitude of stars in a clear night sky away from street lights. Many young children will not have experienced this so if they go away with the school and there is an opportunity for them to do this, then they will be amazed.

Teacher Tip: The sciences are all about awe and wonder: don't undersell this facet.

Children find the concept of a spherical Earth very tricky. After all, we have little everyday experience that suggests we live on a sphere.

The shape of the Earth


The concept of the Earth rotating on its own axis is not at all easy. We are living on a sphere spinning around at high speed (about 700 mph in the UK).

Firstly, it does not look like we are moving at all and secondly, it looks just like the Sun moves around us, rather than vice-versa! Big questions are used as a way of helping children think carefully about such things.

The reason we do not have any sense of the motion is linked to relativity – everything local moves with us. We do not have an idea we are moving unless we can see something that isn't or is moving at a different rate. This is why, when we are sitting on a train at a station and the train next to us seems to move, we can't tell if it is our train moving or the neighbouring train. In order to know, we have to look at the platform and if that it still, we are certainly not moving.

Why do we get day and night?


It is very common for children to think that the Moon is only in the sky during the night time.

When is the moon visible?


The immediate space around us seems rather full of plants, houses, people and chairs, amongst other things. So it's rather hard to imagine that the universe is mostly empty. Many diagrams of planetary systems and other astronomical objects

It is mostly space


Why orbiting objects keep orbiting, and don't either stop or just fall down can be an issue. Here it's phrased in terms of artificial satellites, but the same arguments apply to moons orbiting around planets, planets orbiting around stars, or stars orbiting around galactic centres.

What keeps satellites up?


What keeps satellites going?


Teacher Tip: These challenges and some suggestions for working with them are more fully explained in the Teaching and Learning Issues.

Representing and reasoning: doing physics

This sequence is concerned with developing an understanding of day and night, and up the movements of the planets and Moon. it is rather easy to add lots of additional detail, but the focus should be on movement and illumination.

All of the knowledge about the astronomical objects starts with seeing light that is either emitted by, or reflected from these objects. Here the sun is the only luminous object, so the only one that emits light. Other objects, such as the Earth, the Moon, and the planets all are seen by reflected light. All of these objects are in movement, so figuring out where they are and how the light reflects of them is the key to understanding what can be seen.

Lighting moving objects


What's moving: day and night


Both the moon and the planets appear at different locations at different times. Decoding these patterns of appearance into simple patterns of movement took very smart humans several centuries. Here you are just starting to bring children to notice what phenomena there are, and to begin to show how some common pattern can help to make them of these phenomena.

The moon – our nearest neighbour


Movements in the solar system


  • The Sun acts as a source of light
  • The Moon and planets reflect Sunlight, so we can see them
  • What we see depends on where it is, and the source of illumination

Teacher Tip: Find out more from the Physics Narrative.

Would you recommend this resource to a colleague?

You can easily share this resource via email or social media using the links found at the top of the page.

Earth
is a type of Planet
ONLINE COMMUNITY FORUM

Have a Physics Teaching Question?

Want to ask it in a safe, friendly, knowledgeable environment? TalkPhysics is an online community for anyone involved in the teaching of pre-19 physics.

Visit TalkPhysics