Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
7.15P Explain how the discovery of the CMB radiation led to the Big Bang…
Full specification wording
Topic 7 – Astronomy: 7.15P Explain how the discovery of the CMB radiation led to the Big Bang theory becoming the currently accepted model
The cosmic microwave background (CMB) is faint microwave radiation arriving from every direction in space.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 14 of 18
Study notes
From the checked teaching notes for this specification point.
The idea
The cosmic microwave background (CMB) is faint microwave radiation arriving from every direction in space. Its existence was predicted as leftover radiation from a very hot, dense early universe, and its detection gave strong support to the Big Bang model. The CMB has a characteristic thermal spectrum and is almost uniform, with tiny ripples that match the pattern of structure expected if the universe expanded and cooled from a hot dense state. Competing steady-state models could not explain this pervasive cooled radiation. Because the observation matched the Big Bang prediction so closely, the Big Bang became the currently accepted model. In a multiple-choice question, select the option that links the detected CMB to remnant heat from an early hot, dense universe and to the resulting acceptance of the Big Bang.
What earns the marks
- Identifies the CMB as microwave radiation detected coming from all directions in space.
- Links the CMB to leftover radiation from a very hot, dense early universe predicted by the Big Bang model.
- Explains that the observed CMB matched the Big Bang prediction and so supported that model over alternatives.
- States that this supporting evidence led the Big Bang to become the currently accepted model.
Common mistakes and how to put them right
Treats the CMB as radiation emitted by stars or galaxies today.
Put it right by describing it as remnant radiation from the early universe.
Claims the CMB proved the Big Bang with certainty rather than providing strong supporting evidence that made it the accepted model.
Confuses the CMB with visible light from the Sun.
Put it right by identifying it as microwave radiation filling all of space.
Exam tips
- Read all options before choosing and eliminate any that describe the CMB as starlight or as proof rather than supporting evidence.
- Look for the option that names both the hot, dense early universe and the shift to the Big Bang as the accepted model.
- Check that the chosen option keeps the CMB as microwave radiation, not visible or radio waves from a single source.
Try the lesson
The start of the Topic 7 – Astronomy: 7.15P Explain how the discovery of the CMB radiation led to the Big Bang theory becoming the currently accepted model lesson, made from checked teaching notes for this specification point.
Have a go first
Why is the cosmic microwave background radiation regarded as strong evidence for the Big Bang theory?
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