What on earth is 42? Mark Vernon It's 30 years since Douglas Adams' The Hitchhiker's Guide to the Galaxy made its debut on BBC radio, but its most famous mystery is still waiting to be resolved. The radio series - which subsequently became both bestselling book, television series and film - traces the travels around the galaxy of Arthur Dent, after the earth is destroyed to make way for a "hyperspatial express route". Possibly the most famous line in the whole book is the "answer to life, the universe, and everything" given by the supercomputer, Deep Thought. I cannot share it with anyone and the secret must go with me to the grave Stephen Fry Claims to know the 42 secret For seven and a half million years, this stupendously powerful, office-block of a machine had whirred. When it came to announcing what it had discovered, crowds had quite understandably gathered. "You aren't going to like it," Deep Thought warned. "Forty-two," it said, with infinite majesty and calm. Ever since, speculation has been rife as to what Adams meant. There is the "paperback line theory" - 42 apparently being the average number of lines on the page of a paperback book. Was Adams paying homage to the medium of his success? Then there is the "Lewis Carroll theory" - Adams celebrating Carroll's use of the number in Alice in Wonderland. Numerical base 13 In the book, there is Rule 42 which says that anyone taller than a mile must leave the court immediately. That becomes a problem for Alice when she eats some mushrooms. There is another theory that rests on a complex allusion to 42 in numerical base 13. It sparked Adams' retort: "I don't write jokes in base 13." Douglas Adams never revealed the secret of number 42 Tragically, Douglas Adams died in 2001. So what does Stephen Fry, a close friend, voice of the audiobook, and possibly one of the most intelligent admirers of The Hitchhiker's Guide think? "Of course, it would be unfair for me to comment," he confides. "Douglas told me in the strictest confidence exactly why 42. The answer is fascinating, extraordinary and, when you think hard about it, completely obvious. Nonetheless amazing for that. "Remarkable really. But sadly I cannot share it with anyone and the secret must go with me to the grave. Pity, because it explains so much beyond the books. It really does explain the secret of life, the universe, and everything." But the notion that a computer could provide an answer to the meaning of life is ridiculous, explains Michael Hanlon, author of The Science of The Hitchhiker's Guide to the Galaxy. Even if every existing atom were co-opted into a mind-bogglingly vast computational matrix, it still wouldn't be able to calculate every possible permutation on a chess board, let alone anything truly complex. Fundamental questions There is still hope that science might come up with answers to the big questions. "Of all the ways of looking for meaning, science has answered the most questions so far," Hanlon continues. "It has triumphed at explaining many things. However, it hasn't provided answers to the most fundamental questions like why we are here, what is the universe for. But just because it hasn't yet, doesn't mean it can't or won't." In acting as if life has meaning, we will find, thank God, that it does John Cottingham Philosopher Having said that, it is possible that questions of meaning are simply of a different sort to questions of matter, the physical world in which science has proven so powerful. If so, asking why there is something rather than nothing with mathematics might make no more sense than asking whether a triangle is happy or whether the rocks in the asteroid belt are friends. Similarly, cosmologists like Stephen Hawking once thought physics would come to know the mind of God in a "theory of everything". He now doubts that is possible. "Though we haven't run up against a class of questions that we couldn't answer yet," adds Hanlon. With fiendishly difficult phenomena, like consciousness, scientists have yet to exhaust all their theories. But could there be a serious side to the answer 42? Might there be method in Deep Thought's madness? Wise joke? The answer can be interpreted in two ways. One is that it is a bad joke, implying that there simply is no answer, no meaning, no sense in the universe, and you would be no worse off if you jumped into the nearest black hole. But the other interpretation is that the joke was wise. It shows that seeking numerical answers to questions of meaning is itself the problem. Digits, like a four and a two, can no more do it than a string of digits could represent the poetry of Shakespeare. Fans have come up with numerous theories since Shakespeare's work was the product of a life, and a life lived to the full. Meaning too might only emerge from such fulsome engagement. To put it another way, life is a gift. It is good. It flourishes in experiences like love, explains John Cottingham, professor of philosophy at the University of Reading, and author of On the Meaning of Life. He believes that philosophy can no more provide meaning than science can. This is because life's giftedness, its goodness and its loveliness are essentially spiritual qualities. They can be assessed by rational enquiry. But they cannot be accessed by the cool calculations of reason. They must be experienced. To put it another way, when the poet William Blake urged us "to see a World in a Grain of Sand", he was not suggesting anything literal. Rather, his words captured something of the world transfigured through beauty and meaning. For Prof Cottingham, this is what it means to have faith. "For in acting as if life has meaning, we will find, thank God, that it does." Mark Vernon is the author of 42: Deep Thought on Life, the Universe, and Everything.