42

In Hitchhikers Guide to the Galaxy, Deep Thought is the second most powerful computer in the universe of space and time. Millions of years ago there lived a race of "hyperintelligent" beings. Their favorite pastime (or 'timepass' to all you Mumbaikars) was a game called Brockian Ultra Cricket. The game involved suddenly hitting people for no apparent reason and then running away. Besides this they spent their time bickering over the meaning of life. They got so fed up with this bickering, that they decided to build themselves a super computer and ask it to figure out the meaning of life. They build a computer called Deep Thought. And it does just that. It thinks. And it thinks. Time goes by and seven and a half million years later Deep Thought pops out the answer to the question and delivers it to the descendants of the people who built Deep Thought. The answer is …42
The problem was that the people didn't know quite what to do with the answer. In fact they did not even know what the question was.
Deep says "So once you know what the question actually is, you'll know what the answer means." Of course the problem with this is that it will take a new super computer and 10 million more years to do the reverse calculation to obtain the question from the answer of 42.