Physics KS3/KS4: Professor Brian Cox - What is the Milky Way?

This video explains what a galaxy is, using the Milky Way as an example.

It explores the composition of a galaxy, emphasising that stars, dust and gas make up only a tiny fraction of the total space.

The concept of dark matter is introduced: what we currently believe dark matter to be and its estimated proportion of the galaxy.

The video demonstrates that science does not have all the answers regarding the Milky Way, and that research into dark matter is the cutting edge of contemporary science.

Teacher notes

Points for discussion

  • Terminology in space physics can be challenging and students often find it difficult to appreciate the relationship between terms like stars, planets, the solar system and galaxies. This clip helps to reinforce the meaning of a galaxy, using the Milky Way as an example.

  • Many students will have preconceptions about what dark matter is, based on science fiction and popular culture. It is important that students appreciate that scientific knowledge increases over time with research and investigation, and that scientific theories and ideas change as more is understood. The continually developing ideas about dark matter - what it is and what proportion of the galaxy it occupies - is a good example of such cutting edge science.

Suggested activities

  • This video could serve as an introduction before students start learning about the composition of stars and how the sun was formed at KS4.

  • After watching the video, students could research how scientists gather information about stars and galaxies. Alternatively, at KS3 or KS4 they could suggest their own questions about dark matter and investigate them.

Curriculum information

Suitable for KS3 England, Wales and NI and CfE Scotland, S1-3 Combined Science and Physics GCSE in England, Wales and Northern Ireland and at National 4 and 5 in Scotland.

More from this series:

Why do we have days, nights and seasons?
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Why do astronomers use 'light years' to measure distance in space?
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Moons in our solar system
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The solar system
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