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© Faculty of Education, Monash University & Victorian Department of Education and Training
Astronomical scale
Critical teaching ideas - Science Continuum F to 10
Level: Moving towards level 8
Student everyday experiences
Students interpret reality from their perspective of the world around them. As a result their
everyday thinking about space and time is often limited to local conditions; often at most
perhaps to hundreds of kilometres or decades of years. Vast distances and times are central
ideas in “The changing earth and its place in space.” But, these ideas are very difficult for
students to grasp; this has very important implications for their learning of ideas about
distances in Space or very long time spans. The universe is so large that it is almost
impossible to imagine and we even use a new unit of distance to describe the vast distances in
the universe. This unit is the light year. Students often find it confusing to express a distance
with the term year as we usually use this term to describe a period of time. This unit of
distance is also poorly understood by most adults.
The scientific view
A light year is the distance that light travels in 1 year. The light from the sun takes about
eight minutes to reach the earth because it is only a relatively short astronomical distance
(about 149 million km) away. The light from distant astronomical objects takes so long to get
to us that we see these objects as they appeared a long time ago.
Our solar system is one of many that make up our galaxy, the Milky Way. Our Galaxy has a
diameter of close to 100,000 light years and contains between 200 – 400 billion stars which
vary in size and brightness and are distributed throughout the galaxy. Our galaxy is one of
probably more than one hundred billion galaxies that make up the Universe. Some distant
galaxies are so far away that their light takes several billion years to reach earth.
The sun is many thousands of times closer to the earth than any other star. Hence it looks
brighter and bigger than any other star. Light from the earth’s nearest star other than the sun
(Alpha Centauri, one of the pointers near the Southern Cross) takes just over 4 years to travel
to earth. The trip to that star would take the fastest rocket we currently have available
thousands of years to complete.
Our solar system originated from a giant cloud of gas and debris left from the explosion of
stars five billion years ago. Everything in the universe and on earth is made of this material.
Scientific evidence implies that some rock near the earth’s surface is several billion years old.
The earth’s surface is shaped by water (including ice) and wind over very long times. The
change is so slow that it is hard to observe rock erosion and soil formation. Biological
evolution is also difficult to observe due to the very slow changes that occur.
Critical teaching ideas
© Faculty of Education, Monash University & Victorian Department of Education and Training
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Space is so large that we use a completely different unit to represent distance; the
light year which is the distance that light travels in one year. (This is 65,700 times the
distance from the earth to the sun.)
The Universe is so large that it is almost impossible to imagine.
It has been such a long time since the Universe and even the Earth first came into
being that our lifetime is insignificant.
Some changes are so slow they are very hard to see in one lifetime for example,
evolution, soil formation and rock erosion.
Students are often fascinated with statistics which describe space and time. Through
discussion their ideas can be explored. In order to understand the ideas students need to
explore visual scale models and timelines, and their understanding is further enhanced if they
create these themselves.
Teaching activities
Promote reflection on and clarification of existing ideas.
Cards depicting astronomical bodies (or events in time) can be used to discuss and explore
student preconceptions of the correct order of objects from the students’ school, time etc.
Practice using and build the perceived usefulness of a scientific model or idea.
Student could construct a time line to gain perspective of the vastness of time and our lifetime
in reference to it. Examples of timelines are ‘the origins of the solar system’ and ‘life on
Earth’. If a helpful scale is used a time line representing the age of the earth can be displayed
around the walls of their classroom.
Students could construct a scale model of the solar system with both distances and size of
planets to scale. If an orange is used to represent the size of the sun then the model of the
solar system should fit into the size of an average playground.
The closest star to earth other than the sun is Alpha Centauri. Students can build scale model
which includes the distance between the earth and the sun and the earth and Alpha Centauri.
© Faculty of Education, Monash University & Victorian Department of Education and Training
Image adapted from: http://bendiken.net/images/2006/20060824-solarsystem-scale3.jpg
Clarify and consolidate ideas
A website which may help students to gain some understanding of the relative distances of
very small and very large objects is ‘Powers of 10’ http://www.powersof10.com/.
Students can use an online calculator to construct scale models at the Science Exploratorium:
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Build a solar system
Students can explore a variety of sites useful for the investigation of astronomical distance. A
good selection is available at the Vendian site:
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Solar System Scale Model Meta Page
Further resources
Science related interactive learning objects can be found on the FUSE Teacher Resources
page.
To access the interactive learning object below, teachers must login to FUSE and search by
Learning Resource ID:
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The wonders of our universe: space traveller - students can explore our place in the
universe from a spaceship. They can see where planet Earth and the solar system fit within a
spiral galaxy containing millions of stars.
Learning Resource ID: Y9CY8C