matrix in his brain. He attempts to discover The Ultimate Question by extracting it from his brainwave patterns, as abusively suggested by Ford Prefect, when a Scrabble-playing caveman spells out "forty two". Arthur pulls random letters from a bag, but only gets the sentence "What do you get if you multiply six by ?" Six times nine is actually fifty-four; the answer is deliberately wrong for that question because the question was miscomputed. The program on the "Earth computer" should have run correctly, but the unexpected arrival of the Golgafrinchans on prehistoric Earth caused input errors into the system—computing the wrong question (because of the garbage in, garbage out rule). Therefore, the question in Arthur's subconscious was invalid all along. Quoting Fit the Seventh of the radio series, on Christmas Eve, 1978: Some readers who were trying to find a deeper meaning in the passage soon noticed a certain veracity when using base-13; 610 × 910 = 5410, which can be expressed as 4213 (i.e. 54 in decimal is equal to 42 expressed in base-13). When confronted with this, the author claimed that it was a mere coincidence, stating that "I may be a sorry case, but I don't write jokes in base 13." In Life, the Universe and Everything, a character named "Prak," who "knows all that is true," confirms that 42 is indeed The Answer, and that it is impossible for both The Answer and The Question to be known in the same universe, as they will cancel each other out and take the Universe with them—to be replaced by something even more bizarre (as described in the first theory) and that it may have already happened (as described in the second). Though the question is never found, 42 is the table number at which Arthur and his friends sit when they arrive at Milliways at the end of the radio series. Likewise, Mostly Harmless ends when Arthur stops at a street address identified by his cry of, "There, number 42!" and enters the club Beta, owned by Stavro Mueller (Stavromula Beta). Shortly after, the Earth is destroyed in all existing incarnations. Reasoning Douglas Adams was asked many times why he chose the number 42. Many theories were proposed, including that 42 is 101010 in base-2 binary code, that light refracts through a water surface by 42 degrees to create a rainbow, or that light requires 10−42 seconds