Dodecahedron universe, conceptual illustration. This model, where the universe is finite and shaped as a dodecahedron has been put forward to explain the measurements of the cosmic microwave background (CMB). The CMB is the relic radiation from the Big Bang billions of years ago at a time when the universe was 380,000 years old. Tiny changes in the temperature in the CMB contain information about the evolution and structure of today's galaxies.