GCSE Physics resources
AQA GCSE Space physics
Compare identifiable spectral lines, then distinguish what was observed, what it supports and what remains unexplained.
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Compare identifiable spectral lines, then distinguish what was observed, what it supports and what remains unexplained.
Before you revise
Choose an answer from memory. Your result tells you what to watch for in the guide.
Core revision guide
Compare identifiable spectral lines, then distinguish what was observed, what it supports and what remains unexplained.
Scope: 8463 Physics only · Foundation and Higher
An element has a characteristic pattern of laboratory wavelengths. If matching galaxy lines appear at longer wavelengths, the spectrum is red-shifted, indicating recession in the GCSE interpretation. More distant galaxies generally show larger red shift and greater recession speed. The distance trend supports expansion of space, rather than an explosion from Earth at the centre.
Scope: 8463 Physics only · Foundation and Higher
Extrapolating expansion backwards supports a universe that was once much smaller, denser and hotter: the Big Bang model. Red shift is observational evidence for expansion. Cosmic microwave background is useful enrichment corroborating the hot early universe; advanced cosmological equations are not required to explain this GCSE evidence.
Scope: 8463 Physics only · Foundation and Higher
Since 1998, observations of distant supernovae have suggested that the universe’s expansion is speeding up. These observations extend a constant-expansion picture. GCSE scope asks students to distinguish the evidence from the unresolved cause: dark energy and dark matter are names used in current models, while their nature remains unknown. Do not treat a proposed cause as a directly observed substance.
Misconception clinic
Read each belief, say what is wrong with it, then compare your correction.
Tempting idea: The line was destroyed.
Use instead: The line is still identifiable. Longer matched wavelengths indicate red shift.
Tempting idea: Dark energy has been directly photographed causing every red shift.
Use instead: Its nature is not directly established that way. This states the evidence and its limit.
Retrieval practice
Explore the relationship
Compare an observed red shift with the red shift predicted by Hubble’s law for the selected distance.
Model scope: Optional numerical red-shift/Hubble-law enrichment
What to notice: use the readout to describe how one variable changes when the other is controlled.
Worked examples
Apply red shift and the expansion pattern in the worked reasoning, then try the changed-context questions below.
Scope: 8463 Physics only · Foundation and Higher
The light is red-shifted, so the galaxy is moving away.
Scope: 8463 Physics only · Foundation and Higher
The trend shows more distant galaxies are generally receding faster, supporting an expanding-universe model.
Scope: 8463 Physics only · Foundation and Higher
If the universe is expanding, it was smaller, denser and hotter in the past, consistent with the Big Bang model.
Exam precision
Do this: State the measured spectral change before the inference. Separate the observed expansion pattern from proposed explanations of its cause.
Independent practice
Write an answer before opening the marking guidance. Then edit the exact phrase or step that would gain the next mark.
Scope: 8463 Physics only · Foundation and Higher
Original PhysicsUK mark scheme: Point 1 (1 mark): Matched spectral lines occur at longer wavelengths. Point 2 (1 mark): This indicates recession of distant galaxies. Point 3 (1 mark): More distant galaxies generally recede faster, supporting expansion. Award each distinct point once. Accept equivalent scientifically correct wording. No half marks.
Model answer: Matched lines are red-shifted. Distant galaxies are receding, and recession increases with distance, supporting expansion.
Scope: 8463 Physics only · Foundation and Higher
Original PhysicsUK mark scheme: Point 1 (1 mark): Distant-supernova observations since 1998 suggest expansion is speeding up. Point 2 (1 mark): They do not establish the physical nature/cause of dark energy or dark matter. Award each distinct point once. Accept equivalent scientifically correct wording. No half marks.
Model answer: Supernova observations suggest accelerating expansion, but the physical nature of the proposed causes remains unknown.
Questions pupils ask
No. Red shift supports expansion; supernova observations indicate acceleration. The nature and cause associated with dark energy remain uncertain.
Useful next steps