Daily lessons coming soon
Beginning Monday 20 April, BBC Bitesize will publish daily online lessons for all ages. We'll also have a new dedicated TV channel full of learning content, podcasts on BBC Sounds and loads of educational video on iPlayer.
The study of atomic absorption spectra allows us to determine the chemical make-up of stars. It shows that galaxies are moving away from us in an expanding Universe.
Watch this animation for a summary of step three.
Ada the science app explains the expansion of the universe