Reflecting on a clever idea

The other day I went with a friend to see a movie in a fairly large movie theatre. Just as my friend and I were getting up to leave we happened to see, mounted high up on the back wall, just below the projection booth, a big bright display that was streaming text messages in red LED lights. And all the text was backwards, reversed left to right. We could make out a message that was saying something like “Thank you for using the reflection message system” (I can’t remember the exact words).

After about ten seconds I suddenly realized what I was looking at, and why it was there, and that I was seeing something incredibly clever. I asked my friend if she could figure out what it was for. To my surprise she could not, so I told her. Shortly after that I met up with some other friends – really smart friends – and told them what we had seen, and asked them if they could figure out why it was there. And they couldn’t either.

So today I posed the same question to an entire room full of really smart computer science graduate students. To my amazement not one of them could figure out the purpose of the thing I was describing, no matter how long I gave them to work it out.

So I guess I must have been in some sort of unusual space in my head, that I was able to realize right away what I was seeing in that movie theatre. Or, far more likely, I just got lucky.

Can you figure it out?

4 thoughts on “Reflecting on a clever idea”

  1. Editor’s note: Sally got the answer right away (of course – she’s a genius), but I’m hiding her answer temporarily just to see if anybody else gets it. -Ken

  2. I’m not sure if this is really what it’s for, but you could put captions on the display and give people pieces of glass or plexiglass (probably attached to the seats with a hinge) so that they could superimpose the reflection of the text on the movie. If you were focused on the movie, the text might be a little blurry, though.

  3. until i reread the post and saw that the LEDs were hung in the back of the theater (and not outside in the lobby for example) i had a variety of sublime to ridiculous postulates.

    my favorite (and equally sublime as ridiculous) was that the display was a clear view into the mind’s eye of the sign itself.


    anyway, my guess is it’s a key part of a closed caption device.

    a brief google search revealed this:

  4. When the movie has finally finished playing, the red lights reflect off of the screen in front of you, showing the text in the correct orientation.

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