An astrophysicist studying high-redshift active galactic nuclei (AGN) observes that the characteristic Lyman-alpha emission line is systematically shifted toward longer wavelengths, with greater shifts observed for more distant sources.
Explain how this spectral shift provides key evidence for the Big Bang theory.
53 exam-style questions on Edexcel GCSE Physics 7.2 The Universe and red-shift. Each one has a worked solution and a mark scheme showing where the marks go.