Douglas Adams was asked many times why he chose the number 42. Many theories were proposed, including the fact that 42 is 101010 in binary code, the fact that light refracts off water by 42 degrees to create a rainbow, the fact that light requires 10^−42 seconds to cross the diameter of a proton. Adams rejected them all. On 3 November 1993, he gave an answer on alt.fan.douglas-adams:

"The answer to this is very simple. It was a joke. It had to be a number, an ordinary, smallish number, and I chose that one. Binary representations, base thirteen, Tibetan monks are all complete nonsense. I sat at my desk, stared into the garden and thought '42 will do'. I typed it out. End of story."