What is the solution to the wild and unsolved problem proposed by Greg?

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Discussion Overview

The discussion revolves around a riddle posed by a participant named Greg, which involves a sequence of entering and exiting through various points. Participants explore different interpretations and potential answers, including concepts from physics, biology, and everyday objects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that the riddle could refer to airport security checkpoints.
  • Others propose that it might describe a lumped element in an alternating current circuit, where the "starts" and "ends" are equivalent.
  • One participant suggests that air is the answer, entering through the mouth and exiting through the nose.
  • Another proposes water flowing through a Y-shaped conduit.
  • A Mach-Zehnder interferometer is mentioned as a fitting answer, with a detailed explanation of its operation provided by a participant.
  • Some participants debate whether the beams of light in the interferometer remain unchanged or become different upon recombination.
  • One participant humorously suggests that the answer could be pants, referencing a previous comment.
  • Another participant considers the heart as a possible answer, describing the flow of blood through its chambers and arteries.
  • There is also mention of the excretory system as a potential interpretation, though one participant expresses uncertainty about this idea.

Areas of Agreement / Disagreement

Participants express a variety of interpretations and potential answers, with no clear consensus emerging. Multiple competing views remain throughout the discussion.

Contextual Notes

The riddle's ambiguity leads to differing interpretations, and some participants note that the question itself may not have a definitive solution.

Greg Bernhardt
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Enter through one, exit through two, then enter through two, exit through one.
What is being enter/exited?
 
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What is being enter/exited?
Airport security checkpoints?
 
1 and 2

2 and 1
 
A lumped element in a alternative current circuit :)
1 and 2 are its "starts" and "ends", which are equivalent in an alternative current circuit...
 
my answer is air. air enter in our mouth (which is one) and can exit through our nose (which has two holes [sorry for the bad terminology] and opposite as well.
 
Water in a conduct with form of Y?
 
A Mach-Zender interferometer. I don't know if it is the answer you're looking for, but it fits perfectly.

Njorl
 
What about elevator? Enter "though" first floor, exit through "second", then vice-versa and go home... eh? :wink:
also could be a train: enter at station A through the left door, exit at station B through right door, then from B to A in a different manner...

however, a capacitor in AC circuit fits more...
 
Originally posted by Njorl
A Mach-Zender interferometer. I don't know if it is the answer you're looking for, but it fits perfectly.

Njorl
what is A Mach-Zender interferometer?
 
  • #10
In a Mach-Zehnder (I spelled it wrong initially) interferometer, a single beam of light enters, is split into two beams which travel identical pathlengths through an electro-optically active material, such as lithium niobate or gallium arsenide, then recombined. While the beams are separate, one of them is subject to a slight perturbation. This usually takes the form of an applied electric field. The index of refraction that one beam experiences is slightly alterred, making it experience a slightly different path length. With the correct bias, you can induce a pi/2 phase shift in one arm of the interferrometer. This allows you to modulate the throughput signal from 0-100% at very high speeds (>100 GHz).

Edit - Just wanted to add, I worked on a rib-waveguide version of this. When I read the riddle, I thought of it immediately. We made it by combining elements we already designed - a 1 to 2 splitter and a 2 to 1 combiner - one entrance two exits, two entrances one exit.

Njorl
 
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  • #11
dare i to argue that the first beam of light is different from the end product when the two separated beam combined?
 
  • #12
Originally posted by loop quantum gravity
dare i to argue that the first beam of light is different from the end product when the two separated beam combined?

In the "on" state, the beam would ideally be unalterred. Besides, when a child walks into school in the morning and leaves in the afternoon, is it the same child?

I'm sure there is a better answer. I just can't think of it because I have my MZI on the brain.

Njorl
 
  • #13
Originally posted by Njorl
In the "on" state, the beam would ideally be unalterred. Besides, when a child walks into school in the morning and leaves in the afternoon, is it the same child?

I'm sure there is a better answer. I just can't think of it because I have my MZI on the brain.

Njorl
but you said: " While the beams are separate, one of them is subject to a slight perturbation."- therefore i assume the beam is separated to two beams which is encouters to something that changes something in it therefore when they combine they are different from each other.
 
  • #14
A heart?

Enter through one right atrium, exit through two pulmonary arteries, enter through two pulmonary veins, exit through one aorta?

(It would work better if I could say, enter through one vena cava, but there are 2 of those.)
 
  • #15
don't think is the blood in the heart, since blood from the right atrium, exit through 1 pulmonary trunk, then enter 2 pulmonary arteries.

i was thinking about excretory system too, but too lazy... the question is kinda ambiguous.
 
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  • #16
Excellent brain teaser -- much better than all those ones that can be googled.

But are you sure the answer isn't pants (Achy47's second answer)?
 
  • #17
One of these days Greg is going to make up something totally wild, with no solution in mind, just to see if we can solve it anyway.

Njorl
 
  • #18
Originally posted by Njorl
One of these days Greg is going to make up something totally wild, with no solution in mind, just to see if we can solve it anyway.

Njorl

haha the answer is pants! Achy47 had the idea but never really came out to say it! .5 points for him!
 

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