A computer model follows a large region of the Universe as space expands. The volume of the region increases, and the model adds matter so that the amount of matter increases by the same factor. The model can represent either the Big Bang theory or the Steady State theory.
Which identifies the theory represented and explains the effect on the average density?
Steady State; the density stays constant because matter and volume increase by the same factor.
Big Bang; the density stays constant because matter and volume increase by the same factor.
Steady State; the density increases because created matter accumulates as the region expands.
Big Bang; the density decreases because the larger volume spreads out the added matter.
94 exam-style questions on Edexcel GCSE Physics 7.2 The Universe and red-shift, covering 7.2.1 Big Bang and Steady State theories, 7.2.2 Evidence for the Big Bang, 7.2.3 The Doppler effect and red-shift, 7.2.4 Red-shift as evidence for an expanding Universe, and 7.2.5 The CMB and the accepted model. Each one has a worked solution and a mark scheme showing where the marks go.