For decades, cosmic inflation has been central to our account of cosmology — and the saviour of the Big Bang theory itself. The theory proposes that in the first microseconds of the universe it expanded 27 orders of magnitude in a tiny fraction of a second. Without it the Big Bang fails to explain the universe’s uniformity, the flatness of space, and the evenness of the cosmic microwave background radiation. But a growing and influential group of critics reject the theory altogether. We have no explanation for the force required to create cosmic inflation, nor for its coming to an end. Nobel prize-winning theoretical physicist Roger Penrose has gone so far as claiming that cosmic inflation 'has been falsified'.

Should we give up on cosmic inflation as a speculative theory constructed to overcome observations but which has no experimental support and fundamental theoretical flaws? If we abandon cosmic inflation, are there alternative accounts of the universe that we might uncover? Or is cosmic inflation essential to our whole account of the universe and one which we cannot afford to give up?

Nobel laureate, joining us from Oxford, Roger Penrose, physicist uncovering the origins of the universe Neil Turok, and TIME 100 astrophysicist Priya Natarajan debate cosmic inflation.