Neurosurgeon Dr Eben Alexander was convinced out-of-body experiences were hallucinations - until he went into a coma himself and had what he now believes was a glimpse of heaven. Dr Alexander, who has taught at Harvard Medical School, reveals many others have also seen what he described. Dr. Alexander: A near-death experience will change your life in more ways than one. It means you have survived a serious illness or a major accident, for one thing. But the aftermath ... can be even more significant. For me, it was as if my old world was dead and I had been reborn into a new one. Coping with that is hard: how do you replace your old vision of the universe? Many people are going through similar versions of what I went through, and the stories I have heard from other near-death experience witnesses give me courage every day. They are a constant corroboration of everything that was revealed to me - how we are loved and cherished much more than we can imagine, how we have nothing to fear and nothing to reproach ourselves for. If you have never seen yourself as a spiritual person, and perhaps did not even believe in God, this new dimension to your understanding has an even greater impact. One of the most extraordinary things about my own glimpse of heaven was that, back in this world, no one was aware of the transformation that I was undergoing. All the monitors and sensors and computers could detect no activity: my brain was flat-lining. New knowledge like this changes us for ever. We evolve into someone fresh.