lesson 23

This lesson introduces redshift as evidence that the Universe is expanding, then develops Hubble’s Law and uses it to estimate the age of the Universe. Learners move from an accessible Doppler-effect starter to spectral-line interpretation, a balloon-model activity, proportional calculations and discussion of the Universe’s possible future. Emphasise that space itself is expanding, that the effect has no central point, and that the age estimate is approximate. Use questioning and the plenary quiz to check understanding throughout.