## M Puzzle: Time's A-Wastin'

### by C. Scott Ananian

Each clock spells out a different message with its second hand, using a different encoding scheme:

• Clock 1: The second-hand of the clock pauses about once per minute, staying at one second mark for two seconds instead of the usual one. It will then jump ahead two seconds to stay in time. The second at which it stops corresponds to a letter of the alphabet, with second '1' representing 'A', second '2' representing 'B', and so on. This encodes the complete alphabet using seconds 1-26. There is no word-break character; you'll have to figure those out yourself. (Note that, where it won't confuse the message, we may stop more than once per minute to speed things up. For example, if signalling "EH" we won't require the second-hand to pass 12 between the E and the H.)
The message is UMBERTOECO.
• Clock 2: The second-hand ticks N times for the Nth letter of the alphabet, and then pauses. "ABC" would thus be one tick, a pause, two ticks, a pause, three ticks, pause, and then we'd start over by ticking once and pausing.
The message is BUCK.
• Clock 3: The second-hand jumps either forward or backwards once every two seconds. For this encoding, ignore whether the jump is forwards or backwards. The hand will jump N seconds to indicate the Nth letter of the alphabet. (We use feedback to select whether each jump is forwards or backwards to keep the clock tracking the correct current time.) So the message "ABC" may be represented by the clock jumping forward one second, then jumping forward two seconds, then (likely) jumping backwards three seconds. Or it could jump forward one second, backwards two seconds, and forwards three seconds.
The message is HELLER.
• Clock 4: This is another binary encoding. Ignore the size of the steps: forward steps mean '1' and backwards steps mean '0'. The message is encoded in ASCII. I thought of using EBCDIC here, but that would be just Too Evil. (The size of the jumps is random, but modulated with feedback from the current time to ensure that, over the long run, the clock correctly tracks the current time. We use a "big step" back if we're currently running fast, or a "little step" back if we're slow, and so on.)
The message is MARQUEZ.
• Clock 5: The second-hand of the clock always moves either 3 seconds forward or one second backward. Furthermore, the movements come in pairs: either a forward-then-backwards pair or a backwards-then-forwards pair. If you take the forward-then-backward movements as '1' and the backward-then-forwards movements as '0' you will get a binary string representing the message in ASCII. For example, to send the letter 'A', which is the ASCII code 65, or 0100 0001 in binary, the second hand will move as BFFBBFBF BFBFBFFB, where B represents a backwards movement and F represents a forwards movement. Note again how zeros in the binary/ASCII representation become BF movements and ones become FB. The pairing ensures that clock continues to keep accurate time (exercise left to the reader). In ASCII, the high three bits are always '010' for an all-upper message; hopefully you noticed the repeated BFFBBF patterns which this caused.
The message is UPDIKE.
• Clock 6: The second-hand ticks out its message in morse code. A jump of one second forward is a dot, and three jumps of one second forward is a dash. A jump of three seconds indicates an intracharacter space (between dashes and dots), and a jump of five seconds indicates an intercharacter space. A jump of 10 seconds is a word boundary. If you could hear the clock tick, you'd probably get this one right away.
The message is L ENGLE.

Notes for the animated GIF version installed in 2010 by the archivists of Beginner's Luck: The following clock patterns were modified in order to make their cycles come out to nice fractions of a whole number of minutes, to reduce the size of the animations: The pauses in clock 2 were increased from 2 seconds to 3 seconds to make the length of the encoding 45 seconds. Clock 4 has an extra 4 seconds frozen at the end of each minute to make the cycle come out to 60 seconds. The word boundaries on click 6 were reduced from 10 to 9 seconds to make the length of a cycle 90 seconds.

Starting at the list UPDIKE, ECO, L'ENGLE, MÁRQUEZ, BUCK, HELLER you should have noticed that:

• They are all last names of authors of literary fiction.
• The authors have all written a book with the word "time" in the title.
The key to the a-ha is probably L'ENGLE, which should stir childhood memories in at least one person on your team. [Editor's note: or else memories of the beginning of the hunt, where this book was used in 1.4, "Something in Common".]

If you then look up these books in MIT's BARTON library catalog, you will end up with the following books and call numbers:

These call numbers fit into the "scratch marks" left by your boss in exactly one way.

 UPDIKE P S 3 5 7 1 . P 3 4 8 . T 6 9 1 9 9 7 ECO B D 6 3 8 . E 5 4 1 3 1 9 9 9 L'ENGLE P S 3 5 6 2 . E 5 8 . W 7 MÁRQUEZ P Q 8 1 8 0 . 1 7 . A 6 7 4 . L 6 8 1 9 8 8/9 BUCK P S 3 5 0 3 . U 1 7 5 . T 5 HELLER P S 3 5 5 8 . E 4 5 . C 5 7 1 9 9 4

Reading the starred blanks (shaded here) in order, you obtain 998134. This is, in fact, a call number: if you enter this into Barton, you obtain the book "Scary Monsters and Bright Ideas" by Robyn Williams. The flavortext explicitly states that what your boss was getting at wasn't a "bright idea"; thus the answer is "Scary Monsters".