Welcome to the Planetarium. This museum is open all hours. It houses an incredible collection of astronomical objects, from small, icy moons to vast swirling galaxies. So, how big is the Universe?* How did it begin? And what mysteries does it hold? With specially written text for younger readers, this is an abridged version of the large-format Planetarium. Raman Prinja is professor of astrophysics at UCL. *Space is big. Really big.