Alan Guth: ”The Big Bang theory was never a theory of the ’bang’ itself. It is a theory about the aftermath of a bang.”

In this interview we talk with Alan Guth, theoretical physicist, cosmologist, and one of the fathers of the theory of cosmic inflation. We talk about the early universe and the Big Bang, and why inflation is needed to understand some of their features. We also talk about BICEP2, the experiment that claimed to have found the imprints of gravitational waves produced during inflation (as of August 2015 the signal observed by BICEP2 seems to be due mostly to galactic dust, and this issue was already under consideration at the moment of this conversation). We then turn to how the mechanism of inflation could be realised, and how these realisations can be experimentally tested. Finally, we speak about string theory and how inflation can lead to the generation of a multiverse. This conversation was the basis of a piece of radio explaining inflation for the general public (sorry, in Spanish). You can find it here looking for "La Brújula de la Ciencia s03e36". This conversation took place during the ICHEP 2014 conference at Valencia (Spain) on July 9th 2014. We thank the organisers of ICHEP and professor Guth for helping us in arranging this meeting.