Cosmology

4 marks · Normal

Astronomers use two main types of evidence to support the idea that the universe began with a Big Bang: cosmic microwave background (CMB) radiation and red-shift of galaxies.

(a)

Describe what cosmic microwave background (CMB) radiation is.

[2 marks]

(b)

Explain how CMB radiation and red-shift together act as evidence for the Big Bang theory.

[2 marks]

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(a) CMB radiation is microwave radiation detected from all directions in space, considered to be the leftover energy from the early stages after the Big Bang. · must show definition as leftover energy, mention of microwave wavelength or origin

(b) Red-shift shows galaxies are moving away, meaning the universe is expanding. CMB radiation is leftover energy from the hot, dense origin of the universe. Together they support the Big Bang theory, which states the universe began very hot and dense and has been expanding since. · must show expansion evidence from red-shift, origin evidence from CMB

Also accept: Describes CMB as microwave background from all directions, as leftover from the early Universe

Common mistakes: Only describing one form of evidence; Not connecting CMB and red-shift to the Big Bang

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Marking points

B1 (a) · 1 mark · Defines CMB as microwave radiation from all directions or as background radiation.

B2 (a) · 1 mark · States it is leftover energy from the early universe or Big Bang.

M1 (b) · 1 mark · Links red-shift to expanding universe (expansion evidence).

M2 (b) · 1 mark · Explains CMB as leftover energy and relates both as evidence for the Big Bang theory.

Worked solution

a) CMB radiation is microwave radiation detected equally from all parts of space. It is believed to be the afterglow of the Big Bang, representing energy left over from the early, hot universe.

b) The red-shift of galaxies shows the universe is expanding, as more distant galaxies are receding faster. The CMB is evidence that the universe was once hot and dense and has since cooled as it expanded. Both observations together support the Big Bang theory.