Forty-two is a special number in Geekdom. It is the answer calculated by a humongous supercomputer named Deep Thought over a period of 7.5 million years.

Unfortunately, no one knows what the question is!

Thus, in the book “Answer to the Ultimate Question of Life, the Universe, and Everything”, where this appears, a special computer the size of a small planet was built from organic components and named “Earth” to calculate the ultimate question.

See wikipedia’s page on 42 for the full story!