Consider a large region that expands with the Universe. Its volume doubles.
According to the Steady State theory, what must happen to the mass of matter in this region, and why?
It halves, so that the average density stays constant.
It doubles, so that the average density stays constant.
It stays constant, so that the average density doubles.
It stays constant, so that the average density halves.
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.