An astrophysicist studying a distant active galactic nucleus (AGN) measures a significant positive shift in the wavelength of its characteristic Lyman-alpha emission line.
Explain how this observed redshift, when combined with the observation that redshift increases with a galaxy's distance, provides key evidence supporting the Big Bang theory of the Universe.
53 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.