Nick Payne: from one bereavement to endless universes So vastly problematic was this disparity that Albert Einstein, inventor of general relativity, would spend the final 30 years of his career searching in vain for a way to unify the two theories. Towards the end of his life, Einstein would reflect, "All my attempts to adapt the theoretical foundation of physics to this new type of knowledge failed completely. It was as if the ground had been pulled out from under one, with no firm foundation to be seen anywhere, upon which one could have built. He wasn't alone. For decades, the disparity between relativity and quantum mechanics would remain a mystery. In the mid-Eighties a new theory emerged: superstring theory (or string theory for short). String theory posited that every particle known to us is comprised of minute, vibrating strings. The structural differences between quarks, electrons and so on are a direct result of the vibrational differences between their respective strings. Crucially, the mathematics of string theory was at long last compatible with both general relativity and quantum mechanics. There was just one problem: for the numbers to add up, we would need to accept that our universe was comprised of up-to-and-including 11 space-time dimensions. Pre-string theory, we had been operating under the assumption that there were a mere four; three of space and one of time. In short, we would need to accept that our universe might not be the only universe out there after all. Appropriately, a multitude of multiverse theories began to materialise. As I waded through them, I too began to feel as if the ground had been pulled out from underneath my feet. I decided to contact a number of scientists, chiefly cosmologists and theoretical physicists, for help. The first cosmologist I spoke to informed me that she felt all of the multiverse theories were "b------- supersized" (phew). However, only days later I would speak to a pro-multiverse cosmologist, his multiverse of choice being the Quantum Multiverse. Uncertainty is vital component of quantum theory. By abandoning determinism and focusing instead on probability, quantum theory bravely asserted that certain aspects of Nature are simply governed by chance. If you were able to trap, for instance, a single electron inside a room with both collapsible walls and ceiling, you might think that you would then be able to pinpoint its position with absolute precision. The very act of measurement has introduced a disturbance. According to quantum mechanics, that electron could now be anywhere in the universe. In its simplest form, the Quantum Multiverse is this idea writ large; a multiverse in which endless "copies" of every single one of us are right now living wildly different and slightly similar lives without ever knowing which of us is better or worse off as a result. Everything that can happen does happen and is happening right at this very moment. Looking back, I think I can say with some accuracy that I was seduced by the multiverse because of what it meant for me in light of my father's death. For months, I struggled continually with the startling finality of his absence. I would eventually try to forget him because calling upon his memory would become too difficult. Yet forgetting him felt unnaturally cruel, not to mention selfish. In part, then, Constellations is my attempt to dramatise this dilemma: the urge to remember versus the need to forget. But crucially it is also a play in which the science at the heart of quantum mechanics is explored through the many and varied possible lives of a single couple: cosmologist Marianne and artisan beekeeper Roland. We follow the pair as they fail at first-time small talk, only to then see them succeed. Likewise, we watch as Marianne and Roland break-up and stay together, move in with one another and go their separate ways, embark upon an extramarital odyssey and commit to a life of monogamy. It is a play in which the finitude of their romantic endeavours is both celebrated and mourned. Theoretical physicist Bryce DeWitt once summed up the dangerous duality of the multiverse by saying: "The idea of 10,100+ slightly imperfect copies of oneself all constantly splitting into further copies, which ultimately become unrecognisable, is not easy to reconcile with common sense. Here is schizophrenia with a vengeance. However maudlin it might now sound, the notion that there might be a universe in which my dad was yet to have died was both curiously unhelpful and quietly consoling. Because, of course, there must too be a universe in which he died years ago. A universe in which we have never met. A universe in which he refuses to speak to me. Likewise, out there somewhere, will be a universe in which John Lennon continues to make music and David Cameron never made it beyond the entrance examinations at Eton. In the Quantum Multiverse, chance is our saving grace and our Achilles" heel; we are both wildly autonomous and utterly powerless. Constellations runs until Jan 5 at the Duke of York's Theatre, St Martin's Lane, London WC2N. Tickets: £25 - £37.50 plus 20 day seats at £10 (020 7565 5000; royalcourtatdukes.com)