Modern physics attempts to explain the full complexity of the physical world in terms of three principles: gravity, relativity and quantum mechanics. This raises important fundamental questions such as why is our Universe so large and old? Why is it almost, but not perfectly, homogeneous and isotropic? 

I will describe how recent measurements of the cosmic microwave background radiation made with the Planck Satellite can be used to answer these questions and to elucidate what happened within the first split second of the creation of our Universe. The main aim of the lecture is to persuade the audience that we really can test what happenend shortly after the birth of the Universe.