How Lewis Carroll computed determinants (2023)

(johndcook.com)

176 points | by tzury 14 hours ago

8 comments

  • esafak 14 hours ago
    > Arrange the given block, if necessary, so that no ciphers [zeros] occur in its interior.

    I forgot that cipher used to have a different meaning: zero, via Arabic. In some languages it means digit.

    • vee-kay 4 hours ago
      Fun fact: zero and numerals were not invented by the Arabs. The Arabs learnt the concept & use of mathematical zero, numerals, decimal system, mathematical calculations, etc. from the ancient Hindus/Indians. And from the Arabs, the Europeans learnt it.

      https://en.wikipedia.org/wiki/Hindu-Arabic_numeral_system

      Persian scholar Al Khwarizmi translated and used the Hindu/Indian numerals (including concept of mathematical zero) and "Sulba Sutras" (Hindu/Indian methods of mathematical problem solving) into the text Al-Jabr, which the Europeans translated as "Algebra" (yup, that branch of mathematics that all schoolkids worldwide learn from kindergarten).

    • sundarurfriend 5 hours ago
      In Tamil, it still means a zero. It's usually pronounced like 'cyber' though, because Tamil doesn't have the 'f'/'ph' sound natively.
      • aiuu 5 hours ago
        When someone says "it still means zero" about Tamil when responding to comments about Arabic, two languages which have no shared root and little similarity, what does that mean?

        I think it means HN is full of misleading ideas.

        • Isamu 4 hours ago
          Isn’t the implication that cipher is a loanword? So language relatedness is irrelevant?

          We use “arabic” numerals around the world. So use of an Arabic loan word is unsurprising.

        • gsf_emergency_6 4 hours ago
          So is Gemini. but from it I gather there might be something interesting about a word that "loops back" (geographically) but evolutionarily speaking it was a reworking of _independent_ discoveries of "emptiness"

          Arabic -> Tamil <- Arabic - Sanskrit

          https://en.wikipedia.org/wiki/0#Etymology

        • Razengan 5 hours ago
          Buddy English has no "shared root" with Japanese but we still say sushi.

          What does it mean when someone creates a new account for posting contradictory comments?

          • stackghost 4 hours ago
            English's superpower is readily absorbing new words from other languages.

            Sushi is now an English word. So is hummus, etc.

    • pinkmuffinere 13 hours ago
      lol I never made that connection — in Turkish, zero is sıfır, which does sound a lot like cipher. Also, password is şifre, which again sounds similar. Looking online, apparently the path is sifr (Arabic, meaning zero) -> cifre (French, first meaning zero, then any numeral, then coded message) -> şifre (Turkish, code/cipher)
      • elbear 48 minutes ago
        In Romanian:

        - cifru -> cipher

        - cifră -> digit

      • celaleddin 12 hours ago
        Nice! Imagine the second meaning going back to Arabic and now it's a full loop! It can even override the original meaning given enough time and popularity (not especially for "zero", but possibly for another full-loop word).
        • lupire 4 hours ago
          0 is a full loop!
      • cgio 10 hours ago
        The Turkish password word may be the same used for signature? I suspect so, because in Greek we have the Greek word for signature but also a Turkish loan word τζίφρα (djifra).
        • esafak 9 hours ago
          imza is signature while şifre is password. I imagine the conflation occurred because signatures are used like passwords for authentication...
        • pinkmuffinere 10 hours ago
          Hmm i don’t think that one is related in Turkish — i only know of “imza” as signature, but there could also be other variants.
      • ls-a 13 hours ago
        [flagged]
        • rmunn 12 hours ago
          > All world languages are a deviation from Arabic

          Spouse of a linguist here. That is absolutely not true. To summarize a LOT, there are multiple languages that share common roots, which linguists classify into language "families". If you go to https://en.wikipedia.org/wiki/List_of_language_families#Spok... and sort the list by number of current speakers (which adds up to far more than the population of the world because so many people speak two or more languages), you'll find the top five language families are Indo-European (which includes most European languages, including English), Sino-Tibetan (which includes Chinese), Atlantic-Congo (which includes Bantu and many other languages spoken in Africa, most of which you probably won't have heard of unless you're a linguist or you live in Africa), Afroasiatic (which includes Arabic), and Austronesian (which includes Tagalog, which you might know by the name Filipino).

          It might be possible to claim that the Afroasiatic languages are all derived from Arabic, but the only influence that the Arabic language has had on Indo-European languages such as English is via loanwords (like algebra, for example). This does not make English a derivative of Arabic any more than Japanese (which has borrowed several English words such as カメラ, "kamera", from camera) is a derivative of English. Borrowing a word, or even a few dozen words, from another language does not make it a derivative. English, while it gleefully borrows loanwords from everywhere, is derived from French and German (or, to be more accurate, from Anglo-Norman and Proto-Germanic).

          • awesome_dude 11 hours ago
            Can I also add that "Arabic numbers" - the numbers we use today, are actually of Indian origin, the Arabs translated the Indian logic/math texts into Arabic, and Western society used the Arabic translations (and additions like those of "Algorithm")

            https://en.wikipedia.org/wiki/Hindu%E2%80%93Arabic_numeral_s...

            • inopinatus 11 hours ago
              I have it on consumer-grade authority that the Indians got them in turn from the Shang dynasty, decimal since ca.1200BCE. Thus proving conclusively that numeral systems naturally travel deasil. Ne'er let thine diʒits, goe widdershins.
            • bigstrat2003 11 hours ago
              Also as long as we are going down the terminology nerd rabbit hole: it's Arabic numerals, not numbers. Numbers refers to the abstract concept, numerals refers to the method one uses to write them down.
              • awesome_dude 11 hours ago
                Yeah - I quoted that to show that it was normal usage rather than technical correctness - I also did the same for the name that I didn't have the correct spelling for as I wrote the comment - not sure if I should update it (with your input) or to leave it and let people work down the thread
              • inopinatus 11 hours ago
                it's a cardinal rule
          • ls-a 11 hours ago
            [flagged]
            • 867-5309 11 hours ago
              for fellow non-linguists, that was Ignorantese for "trust me, bro"
        • drivebyhooting 13 hours ago
          This doesn’t sound right. What about Chinese?
          • astrange 11 hours ago
            Basque and Pirahā are the good ones.
          • jjtheblunt 11 hours ago
            i'm quite sure the person was joking
    • jacquesm 12 hours ago
      Dutch too: "Cijfer", German, "Ziffer", French: "Chifre", Spanish: "Cifra".
  • howling 8 hours ago
  • gsf_emergency_6 4 hours ago
  • BobbyTables2 7 hours ago
    Wow, I never realized the cofactor method wasn’t the only one.

    I loathed it and it put me off wanting to get into advanced matrix topics.

    • RossBencina 5 hours ago
      I don't think determinants play a central role in modern advanced matrix topics.

      Luckily for me I read Axler's "Linear Algebra Done Right" (which uses determinant-free proofs) during my first linear algebra course, and didn't concern myself with determinants for a very long time.

      Edit: Beyond cofactor expansion everyone should know of at least one quick method to write down determinants of 3x3 matrices. There is a nice survey in this paper:

      Dardan Hajriza, "New Method to Compute the Determinant of a 3x3 Matrix," International Journal of Algebra, Vol. 3, 2009, no. 5, 211 - 219. https://www.m-hikari.com/ija/ija-password-2009/ija-password5...

      • srean 34 minutes ago
        > I don't think determinants play a central role in modern advanced matrix topics.

        Not true at all. It's integral to determinantal stochastic point processes, commute distances in graphs, conductance in resistor networks, computing correlation via linear response theory, enumerating subgraphs, representation theory of groups, spectral graph theory... I am sure many more

  • kazinator 12 hours ago
    > Dodgson’s original paper from 1867 is quite readable, surprisingly so given that math notation and terminology changes over time.

    Given that Jabberwocky is also quite readable, we shouldn't be too astonished.

  • barbazoo 5 hours ago
    And just like back in university I know how how calculate Determinants but have no clue what one would actually use it for.
    • ComplexSystems 5 hours ago
      Suppose you have (let's say) a 3x3 matrix. This is a linear transformation that maps real vectors to real vectors. Now let's say you have a cube as input with volume 1, and you send it into this transformation. The absolute value of the determinant of the matrix tells you what volume the transformed cube will be. The sign tells you if there is a parity reversal or not.
    • Razengan 5 hours ago
      3blue1brown is your friend
    • RossBencina 4 hours ago
      Form a quadratic equation to solve for the eigenvalues x of a 2x2 matrix (|A - xI| = 0). The inverse of a matrix can be calculated as the classical adjugate multiplied by the reciprocal of the determinant. Use Cramer's Rule to solve a system of linear equations by computing determinants. Reason that if x is an eigenvalue of A then A - xI has a non-trivial nullspace (using the mnemonic |A - xI| = 0).
  • 01jonny01 11 hours ago
    When I'm not cognitively depleted from over working and kids I'd really like to sit down and read this properly.
  • messe 14 hours ago
    HN title filter cut off the initial "How".

    You can manually edit it back in.

    • marcusestes 14 hours ago
      “Drop the ‘how.’ It’s cleaner.”
      • vharuck 13 hours ago
        It gives it a different implication. As I read it, an article titled "Lewis Carroll Computed Determinates" has three possible subjects:

        1. Literally, Carroll would do matrix math. I know, like many on HN, that he was a mathematician. So this would be a dull and therefore unlikely subject.

        2. Carroll invented determinates. This doesn't really fit the timeline of math history, so I doubt it.

        3. Carroll computed determinates, and this was surprising. Maybe because we thought he was a bad mathematician, or the method had recently been invented and we don't know how he learned of it. This is slightly plausible.

        4. (The actual subject). Carroll invented a method for computing determinates. A mathematician inventing a math technique makes sense, but the title doesn't. It'd be like saying "Newton and Leibnitz Used Calculus." Really burying the lede.

        Of course, this could've been avoided had the article not gone with a click-bait style title. A clearer one might've been "Lewis Carroll's Method for Calculating Determinates Is Probably How You First Learned to Do It." It's long, but I'm not a pithy writer. I'm sure somebody could do better.

        • miltonlost 13 hours ago
          "How Lewis Carroll Computed Determinates" is fine and not clickbait because it provides all the pertinent information and is an accurate summary of its contents. Clickbait would be "you would never guess how this author/mathematician computed determinants" since it requires a clickthrough to know who the person is. How is perfectly fine IMO to have in the title because I personally would expect the How to be long enough to warrant a necessary clickthrough due to the otherwise required title length.
          • 867-5309 10 hours ago
            it's not quite McKean's Law so I'll settle for contagious