6.6 The Universe: What is out there?
Use absorption spectra and red shift as evidence for composition, expansion and the Big Bang model.
How to study WJEC GCSE The Sciences
Move from a scientific model to a prediction or method, collect or interpret evidence, show quantitative working and finish with a conclusion whose limits match the data.
Core concepts
Concept 1
Compare absorption spectra to identify elements in stars or nebulae.
Exam cue: Identify the unit, entered tier, supplied reference material, command word and relevant scientific enquiry skill.
Concept 2
Interpret red shift as evidence that distant galaxies are receding.
Exam cue: Match line patterns before discussing composition, then distinguish observed red shift from the inferred expansion model.
Concept 3
Connect expansion evidence and cosmic observations to the Big Bang model.
Exam cue: Use scientific terminology, show quantitative working with units, and connect conclusions to data and the stated model.
Concept 4
Official subtopics: 6.6.1 The origins and the expansion of the universe.
Concept 5
Scientific enquiry and mathematical skills apply in this topic; bold amplification is Higher Tier only.
Risk pitfalls and guardrails
Explaining cosmological red shift as a visible change to red colour rather than shifted spectral lines.
Guardrail: Do not import outgoing 3430QD content, another science route, a fixed required-practical list or unsupported tier and connection assumptions.
Recalling a fact without applying it to the observation, data, practical method or unfamiliar context.
Guardrail: Use the live secure pack: Task A may use groups of up to three; Task B is individual and highly controlled. Two enquiries are selected by the centre from three.
Importing content, required practicals, tier rules or paper structure from the outgoing WJEC or another awarding-body route.
Guardrail: Bold amplification is Higher-only. Units 1-6 may mix tiers, but Unit 7 is untiered.
Memory anchors
Absorption spectrum
Dark wavelength lines produced when atoms absorb specific radiation.
Red shift
Shift of spectral lines toward longer wavelengths.
Recession
Movement of an object away from an observer.
Big Bang model
Model in which the Universe expanded from an earlier hot dense state.
Cosmic expansion
Increase in large-scale separation between distant galaxies.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What does red-shift of distant galaxies show? Use the spectrum or background-radiation evidence without treating a model as direct observation. Test the proposed explanation against every stated fact.
How does red-shift support the Big Bang model? Use the spectrum or background-radiation evidence without treating a model as direct observation. Select the claim supported by the observation.
Answer all questions to submit.
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Move forward only after this module is stable.
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