COSMIC MICROWAVE BACKGROUND (CMB) RADIATION
2 marks · NormalExplain why the cosmic microwave background (CMB) radiation is an important piece of evidence for the Big Bang theory.
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Common mistakes: just stating 'CMB exists' with no link to Big Bang; confusing with other types of waves
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Marking points
B1 · 1 mark · States the CMB is the leftover radiation from the early universe/the Big Bang.
B2 · 1 mark · Explains the afterglow was predicted by theory and matches observations (e.g. wavelength, found everywhere).
Worked solution
The CMB is important because it is the afterglow radiation from the Big Bang, as predicted by theory. Its presence in all directions and its wavelength match what scientists expected if the universe began with a hot, dense state.