Morse Palindromes, or CQ Christian Bök

The longest palindrome in Morse code is “intransigence””, and it was on

First off, here’s the Morse code for the word intransigence:

·· –· – ·–· ·– –· ··· ·· ––· · –· –·–· ·
i  n  t r   a  n  s   i  g   e n  c    e

If you look at it as a simple stream of dits and dahs, then yes, it’s palindromic. But, like comedy, the secret of Morse (or CW) is timing. It’s important to include the spaces between the keyings, or letters become hard to identify as they run together. For a word to truly sound palindromic, it would need to have the same spacing too, and thus have to start and end on Morse codes that were mirror-images.

Not only that, but you get codes which when reversed, become another letter. a (·–) becomes n (–·) when reversed. So things are getting more complex, as we’ve now got to think of:

  1. Words which are both palindromes in the English and Morse code;
  2. Words which are palindromes in Morse, but not when written in English.

With only Convert::Morse and words to guide me, here’s what I found.

Firstly, here’s a Morse code table for reference:

 ! → –·–·––           3 → ···––          a → ·–          n → –·
 " → ·–··–·           4 → ····–          b → –···        o → –––
 ' → ·––––·           5 → ·····          c → –·–·        p → ·––·
 ( → –·––·            6 → –····          d → –··         q → ––·–
 ) → –·––·–           7 → ––···          e → ·           r → ·–·
 + → ·–·–·            8 → –––··          f → ··–·        s → ···
 , → ––··––           9 → ––––·          g → ––·         t → –
 - → –····–           : → –––···         h → ····        u → ··–
 . → ·–·–·–           ; → –·–·–          i → ··          v → ···–
 / → –··–·            = → –···–          j → ·–––        w → ·––
 0 → –––––            ? → ··––··         k → –·–         x → –··–
 1 → ·––––            @ → ·––·–·         l → ·–··        y → –·––
 2 → ··–––            _ → ··––·–         m → ––          z → ––··

From that, you can see that the letters which have symmetrical keyings are:

 " ' ) + , - 0 5 ; = ? e h i k m o p r s t x

So are there palindromic words composed only of the letters E, H, I, K, M, O, P, R, S, T & X? Here are the ones in my words file, longest first:

 sexes rotor toot sees poop peep kook tot
 tit SOS sis pop pip pep oho mom ere eke

(Somewhere, the ghost of Sigmund Freud is going “Hmm …)

When encoded, rotor (·–· ––– – ––– ·–·) has more dahs that sexes (··· · –··– · ···), so takes longer to transmit. So rotor is the longest word that’s palindromic in both English and Morse.

The characters which have valid Morse codes when reversed are:

 " → "             8 → 2             l → f
 ' → '             9 → 1             m → m
 ) → )             ; → ;             n → a
 + → +             = → =             o → o
 , → ,             ? → ?             p → p
 - → -             a → n             q → y
 0 → 0             b → v             r → r
 1 → 9             d → u             s → s
 2 → 8             e → e             t → t
 3 → 7             f → l             u → d
 4 → 6             g → w             v → b
 5 → 5             h → h             w → g
 6 → 4             i → i             x → x
 7 → 3             k → k             y → q

Note how 1…9 reverse to 9…1. c, j & z don’t stand for anything backwards.

So, with only minimal messing about, here are the words that are palindromes in CW:

 ada → nun              ads → sun              ages → sewn
 ago → own              ail → fin              aim → min
 ana → nan              ani → ian              ant → tan
 ants → stan            boa → nov              eel → fee
 ego → owe              eire → erie            eke → eke
 emir → rime            emit → time            ere → ere
 erie → eire            eris → sire            eros → sore
 etna → nate            fee → eel              feel → feel
 fever → rebel          few → gel              fin → ail
 fins → sail            fool → fool            foot → tool
 foots → stool          footstool → footstool  fop → pol
 gel → few              gem → mew              gets → stew
 gnaw → gnaw            goa → now              gob → vow
 gog → wow              got → tow              hoop → pooh
 ian → ani              ids → sui              kans → sank
 kant → tank            keep → peek            kook → kook
 kroger → rework        leer → reef            leif → lief
 lief → leif            loops → spoof          meet → teem
 mew → gem              min → aim              mir → rim
 mit → tim              mom → mom              moor → room
 nan → ana              nate → etna            nerd → urea
 net → tea              nib → via              nit → tia
 nov → boa              now → goa              nun → ada
 oho → oho              otto → otto            outdo → outdo
 owe → ego              own → ago              owns → sago
 peek → keep            peep → peep            pees → seep
 pep → pep              per → rep              pets → step
 pip → pip              pis → sip              pit → tip
 pol → fop              pooh → hoop            poop → poop
 pop → pop              ports → strop          pot → top
 pots → stop            queer → reedy          quit → tidy
 rebel → fever          reedy → queer          reef → leer
 regor → rower          remit → timer          rep → per
 rework → kroger        rim → mir              rime → emir
 robert → trevor        room → moor            rot → tor
 rotor → rotor          rower → regor          runs → sadr
 sadr → runs            sago → owns            sail → fins
 saints → stains        sangs → swans          sank → kans
 sans → sans            seep → pees            sees → sees
 sewn → ages            sexes → sexes          sip → pis
 sire → eris            sis → sis              sling → waifs
 sloops → spoofs        sore → eros            sos → sos
 spit → tips            spoof → loops          spoofs → sloops
 sports → strops        spot → tops            spots → stops
 stains → saints        stan → ants            step → pets
 stew → gets            sting → waits          stool → foots
 stop → pots            stops → spots          strop → ports
 strops → sports        suds → suds            sui → ids
 sun → ads              sung → wads            swans → sangs
 swig → wigs            swigs → swigs          taint → taint
 tan → ant              tang → want            tank → kant
 tea → net              teem → meet            tet → tet
 tia → nit              tidy → quit            tim → mit
 time → emit            timer → remit          ting → wait
 tip → pit              tips → spit            tit → tit
 tog → wot              tool → foot            toot → toot
 top → pot              tops → spot            tor → rot
 tort → trot            tot → tot              tow → got
 trevor → robert        trot → tort            urea → nerd
 via → nib              vow → gob              wads → sung
 waifs → sling          wait → ting            waiting → waiting
 waits → sting          wang → wang            want → tang
 wig → wig              wigs → swig            wot → tog
 wow → gog

So of all of these, footstool (··–· ––– ––– – ··· – ––– ––– ·–··) is the longest English word that is a palindrome in CW. Here is how it sounds at 18wpm: forwards, backwards.