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What do you get when you photocopy a mirror - and *why* ?? (
by RiderOfGiraffes to math science puzzle on March 29, 2019 | 7 comments

I'm finding, repeatedly, that people don't seem to understand the question I'm asking, and I genuinely don't know how to ask it differently. I'm beginning to wonder if this is a difference/distinction that people don't see, and perhaps can't understand.

Try to answer the question without referring to how the photocopier/scanner works, and only refer to what it does.

If you can see the difference, I'd welcome suggestions as to how better to ask the question.


If this is intended as a philosophical question, then it might help to frame it as such. Otherwise you're asking a question about to very physical objects that have very concrete properties that would interact in predictable, if unexpected ways in this scenario. (I think you'd get a view of the inside of the photocopier, if there is enough light reflected for that, depending on the angle of the cameras inside the machine, or just a smear of the sensor bar moving across)

What does a photocopier do that's fundamentally different than "take a certain type of photo, then print it"? Are you wanting to introduce a type of paradox? Is there a greater point here that might be served by a different example?

This feels like something that you found profound at some point?


I can see that you're trying to find the question, and I appreciate your response. Even so, you're still not getting to the question I'm trying to ask, but you have given me a few ideas.

So let me try asking it a different way.


Suppose that I have here a device which, when a leaflet, pamphlet, printout, or other "image" is laid on it, will produce a piece of paper with a copy of the appearance of the object given.

From that alone, without knowing anything about how it works, can you deduce what will be produced when you put a mirror on it?


Is that clearer?


I think it is a little clearer.

Is this partially about if a mirror actually has an appearance of it's own?


... (thinks) ... no, I don't think so.


I don't have time to write out all the reasoning I could try to apply to this right now. I might try to come back to it this evening.

I will say that, as a person that has written software to build systems, that understanding some of the underlying details of how something works has often been helpful in understanding why things do what they do. All abstractions leak, as it were, and there's a cost when they do.

I suspect that getting to the right answer by just reasoning, without actually breaking down how the scanning mechanism works, is potentially building on faulty assumptions, but I don't have the time to work the details on that now.

Something that may be unrelated, but comes to mind: Many people, myself included, scan documents by using a cell phone camera, which would change the result here, by changing how the scanner works. But perhaps that would show up in the way the question is phrased.

Definitely that sort of brain tickler that is probably more interesting to think about than it might have any right to be.


Thinking about the problems you sometimes face by using a camera as a scanner can be a useful way into this question/problem.


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