23. tq-gj*Z/YC?

As seen on the BART today:

jacques binet math problem

Credit: @normanau

That’s blurry, but it says:

Jacques Binet could have read this:


Can you?

I can … kind of.  Mathematician friends help me out. That expression would read: t times q minus g times j multiplied by Z over Y times C.  The variables most likely signify units, and I would wager t=time, j=joules(?), C = coulombs, and q, g, Z, and Y are just for fun.

No, they probably stand for something.  But what?

On a related note: that’s a brilliant bit of brainiac marketing.  I was so intrigued I wrote down the poster in my little notebook, and I even looked up Jacques Binet on wikipedia. Turns out Jacques Philippe Marie Binet was quite a mathematician in the first half of the 19th century.  He made “significant contributions” to number theory and matrix algebra, and he even derived his own theorem, Binet’s Theorem, which is this:

\det(A B) = \det A \cdot \det B

But you’ll have to understand a little about linear algebra to get a sense of what that means.

I’m curious to know what organization is behind this poster.

In other math news, Apostolos Doxiadis and Christos H. Papadimitriou wrote an amusing romp of a graphic novel about logic.  Logicomix: An Epic Search for Truth features interesting puzzles like Hilbert’s paradox and draws on the biography of logic rockstar Bertrand Russell. Stocking-stuffer anyone?


18 responses to “23. tq-gj*Z/YC?

  1. The equation reads

    Division is a forward slash (/); the backslash typically represents a set difference, suggesting that Z is the set of integers.

    The asterisk could represent a dual space or an adjoint.

    “C = coulombs”? Usually, a variable “q” represents electric charge.

    The equation is meaningless without knowing what the variables all signify and, moreover, what their values are. Solving the equation for some value makes the ad fairly useless. I hypothesize that the equation is encrypted text (perhaps the address of a website) that uses “Jacques Binet” as a cipher key.

  2. Hey! I see you found my tweet. Thanks for trying to provide an answer!

    the BART blog unveiled the advertiser behind this, but alas no answer see: http://sfbart.posterous.com/

  3. I see Norman has commented… He was the first to surface a picture of the ad. : )

    It seems not many people have been talking about this one. I did a bit more research, and have come up with the following:

    – I agree with “not Binet” –The backslash like character is most likely a ‘set minus’ character (unicode U+2216). In that case, set theory might be in play on this equation. The only connection I could find between the enigmatic ‘Binet equation’ and set theory was around the Riemann-zeta function (http://www.math.uiuc.edu/~aadixit2/zeta_updated.pdf). Interestingly enough, zeta functions use an uppercase zeta (the captial Z)… Not sure if that has any bearing on this, though. I haven’t seen many set theory equations that take this form.

    – Wolfram|Alpha interprets the “Z\YC” as possibly meaning “Z over yottacoulomb (YC)”… It is possible that the YC is a reference to the measurement of distance travelled by an amp over one second.

    – More thoughts on my Wolfram|Math post: http://community.wolframalpha.com/viewtopic.php?f=20&t=6772#p9288

    The mystery behind WHO put the equation up is solved, but the actual purpose of the equation is not.

  4. This problem has consumed me for the last 24 hrs. I’m not mathematically inclined enough to know this, but I’ve been trying my best to figure it out. Here’s what I have so far.

    Given the Binet reference and the \ character, this has to do with some form of matrix algebra and number sets.

    tq-gj : This could be a mathematical determinant for a 2×2 matrix containing t,g,q,j (read top left to bottom right)
    * : if the * is part of tq-gj, it may indicate a conjugate transpose of said matrix.
    Z : Z in blackboard bold is identified as the set if integers {…,-2,-1,0,1,2,…}
    \ : Indicates a set difference
    C : C in blacboard bold is identified as the set of all complex numbers
    Y : Y could be a set of random numbers (no proof)
    *Z : *Z with Z being in blackboard bold could be the set of all hyperintegers

    Z\YC could indicate the set difference between all integers and some multiplicatve matrix of a complex number set and random number set. throw the * in here (hyperintegers) and its even more confusing.

    As of now, this rabbit hole has taken me into other avenues of abstract algebra and ring theory.. phew.

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  6. This probably doesn’t lead anywhere, but if you take the ASCII values of these characters and look at the three least significant bits of each, you get a number series that starts with 4-1-5… which is the area code of San Francisco… maybe it’s a phone number? 🙂

  7. t 116 74
    q 113 71
    – 45 2D
    g 103 67
    j 106 6A
    * 42 2A
    Z 90 5A
    \ 92 5C
    Y 89 59
    C 67 43

    (415) 762-0297

    • That result requires switching between the final octet and digit somewhat arbitrarily.

      If you stick with only octets (in which case there’d be no way of getting that “9”), then the number would be 415-722-2413. That seems to be a private number (“Hello, this is Sharon. Leave a message at the beep.”)

      If you switch to the final digit, then you’re no longer dealing with the 415 area code, and the area code for 635-362-0297 isn’t in service.


    • What? No, you switched to the decimal halfway through. Should be 415-722-2413.

  8. …and that makes it high quality crap since Binet could not have known about ASCII codes which didn’t come in to existence until a neat century after he died.

  9. Has any tried calling that number???

  10. I get 415 722 2413 (5?)

    char, dec, hex, last 3 bits
    t, 116, 0x74, 4
    q, 113, 0x71, 1
    -, 045, 0x2d, 5
    g, 103, 0x67, 7
    j, 106, 0x6a, 2
    *, 042, 0x2a, 2
    Z, 090, 0x5a, 2
    \, 092, 0x5c, 4
    Y, 089, 0x59, 1
    C, 067, 0x43, 3
    =, 061, 0x3d, 5

  11. 2 months since the last comment…

    Riding the BART today and the poster is still there. Been trying, with the help of a friend, to work this out…

    … we have not got very far.

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