AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
The observed red-shift provides evidence that space itself (the universe)…
Full specification wording
Red-shift (physics only): The observed red-shift provides evidence that space itself (the universe) is expanding and supports the Big Bang theory.
Every distant galaxy is receding from us, and the further away it is the faster it goes.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 4 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Every distant galaxy is receding from us, and the further away it is the faster it goes. At first that looks as though we sit at the centre of an explosion, but the same pattern would be seen from any galaxy, and that is the clue: the galaxies are not flying apart through space, but space between them is expanding and carrying them with it. The balloon model helps here. Dots inked onto a balloon all move apart as it is blown up, and the dots that start furthest apart separate fastest. Its weakness is that the dots sit on a surface while real galaxies fill three dimensions. Run the expansion backwards and everything was once together, which is what the Big Bang theory describes.
What earns the marks
- The observation that distant galaxies are all moving away from us.
- The more distant galaxies receding faster.
- Concluding that space itself, and so the universe, is expanding.
- Running the expansion backwards to a single point as support for the Big Bang theory.
Common mistakes and how to put them right
Concluding that the Earth is at the centre of the universe because everything is moving away from us.
Saying the galaxies are flying outwards from an explosion, rather than that space is expanding.
Offering the balloon model with no weakness stated when the question asks for one.
Treating red-shift as proof rather than as evidence that supports the theory.
Exam tips
- Separate the observation from the conclusion, because questions usually award a mark for each.
- When you use the balloon model, say what it represents well and what it fails to represent.
- Use the word evidence rather than proof when writing about scientific theories.
Try the lesson
The start of the Red-shift (physics only): The observed red-shift provides evidence that space itself (the universe) is expanding and supports the Big Bang theory. lesson, made from checked teaching notes for this specification point.
Have a go first
Observations of red-shift from distant galaxies provide evidence that the universe is doing which of the following?
Listen
Every distant galaxy is receding from us, and the further away it is the faster it goes. At first that looks as though we sit at the centre of an explosion, but the same pattern would be seen from any galaxy, and that is the clue: the galaxies are not flying apart through space, but space between them is expanding and carrying them with it. The balloon model helps here. Dots inked onto a balloon all move apart as it is blown up, and the dots that start furthest apart separate fastest. Its weakness is that the dots sit on a surface while real galaxies fill three dimensions. Run the expansion backwards and everything was once together, which is what the Big Bang theory describes. A strong answer earns marks for these points. the observation that distant galaxies are all moving away from us. the more distant galaxies receding faster. concluding that space itself, and so the universe, is expanding. running the expansion backwards to a single point as support for the Big Bang theory. Exam tip: Separate the observation from the conclusion, because questions usually award a mark for each.
Key words
Say what each word means before you turn the card.
expanding universe
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evidence for the Big Bang
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balloon model
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no centre to the expansion
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See every definition
- expanding universe
- Space itself is expanding and carrying the galaxies with it, rather than the galaxies flying apart through space.
- evidence for the Big Bang
- Running the expansion backwards shows everything was once together, which is what the Big Bang theory describes.
- balloon model
- Dots inked onto a balloon all move apart as it is blown up, and the dots that start furthest apart separate fastest.
- no centre to the expansion
- The same pattern of galaxies receding would be seen from any galaxy, so the Earth is not at the centre.
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