In “The Hitchhiker’s Guide to the Galaxy,” the answer to the ultimate question of life, the universe, and everything is 42. The answer is calculated by Deep Thought, an enormous computer built by hyper-intelligent pan-dimensional beings.
Deep Thought takes 7.5 million years to complete the calculation, only to reveal that nobody actually knows the question being answered. That joke is central to Douglas Adams’s story: a perfectly precise answer is useless when the underlying question has been lost. Deep Thought therefore proposes building an even larger computer capable of discovering the question.
That computer is Earth, designed as a living computational system. Arthur Dent and Ford Prefect become involved in the search for the ultimate question, but the result is confused by events surrounding Earth’s destruction and the planet’s strange history. A later attempted formulation—“What do you get when you multiply six by nine?”—deliberately produces 54 in base ten, underscoring the story’s absurdity.
Adams repeatedly said he chose 42 as an ordinary, funny number rather than a code with a hidden philosophical meaning. The number has since become a lasting science-fiction and internet reference. The key distinction is that 42 is the answer, while the ultimate question itself is never successfully established.