An astrophysicist studying distant superclusters of galaxies measures their redshift parameter, z=Δλλ0\displaystyle z = \frac{\Delta \lambda}{\lambda_0}z=λ0Δλ, and plots it against their distance from Earth, ddd. They observe a strong positive correlation where z z\,z is directly proportional to ddd.
Explain how this proportional relationship, combined with the physical meaning of a positive redshift (z>0z > 0z>0), provides evidence for both the expansion of space and 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.