42 Puzzle

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The 42 Puzzle, as it appeared on pages 80 and 81 of The Illustrated Hitchhiker's Guide to the Galaxy
The 42 Puzzle, as it appeared on pages 80 and 81 of The Illustrated Hitchhiker's Guide to the Galaxy
This printing of The Hitchhiker's Guide to the Galaxy from the late 1990s contains the puzzle on its cover.
This printing of The Hitchhiker's Guide to the Galaxy from the late 1990s contains the puzzle on its cover.

The 42 Puzzle is a game devised by Douglas Adams in 1994 for his popular The Hitchhiker's Guide to the Galaxy series. In the books, 42 is known as The Answer to the Ultimate Question of Life, the Universe, and Everything that Deep Thought, a sophisticated computer constructed by pandimensional beings, returns (after seven-and-a-half million years of calculating). Referencing this, he created a puzzle whose question was unknown, but whose answer is already known to be 42.

The puzzle is an illustration consisting of 42 multi-coloured balls, in 7 columns and 6 rows. According to Douglas Adams (in an interview reprinted at Douglas Adams Continuum), "Everybody was looking for hidden meanings and puzzles and significances in what I had written (like 'is it significant that 6 * 9 is 42 in base 13?'. As if.) So I thought that just for a change I would actually construct a puzzle and see how many people solved it. Of course, nobody paid it any attention. I think that's terribly significant."

The puzzle first appeared in The Illustrated Hitchhiker's Guide to the Galaxy. It was later incorporated into the covers of all five reprinted "Hitchhiker's" novels.

[edit] Questions to the Puzzle

In another interview, the author mentioned that there were 10 solutions to the problem, some of which are:

  • How many spheres are in the diagram?
  • Using Interleaved 2 of 5 encoding, what does the bar code on the white sphere on the left read?
  • Considering red-hued spheres (red, purple, orange, black) as a '1' and those without as a '0', what number does each line represent in decimal form? (In binary, each line reads '0101010', or '42' in decimal form.)
  • What number do the blue-tinted spheres (blue, green, purple, black) spell out? (Similar to a color blindness test.)
  • What position in the grid does Earth occupy?
  • What number is represented by Roman numerals spelled out by the yellow-tinted spheres (yellow, orange, green, black) in the first three rows? (XLII)
  • What is the absolute value of the degree of longitude the Earth is centered on? (It seems to be centered on Latitude 0° and Longitude -42°, and |-42| is 42.) Or simply 42°W when using a suffix. Sometimes East is negative depending on the convention which can be confusing... just like this puzzle. In that case the longitude would be '42'.