Two friends are discussing concepts for a new fantasy story:

A: There exists a magical mirror that leads to a mirrored universe. In this universe, people drive on the left side of the road, and you were a king who was adored by everyone! Unfortunately, you from that universe died in an accident, but that also means that you from this universe can enter it and take his place and live forever as king!

B: But A, haven't you pay attention in _______________ class? You cannot live in the mirror world forever because _______________

What is the problem?

  • 4
    $\begingroup$ Huh? Round here people already drive on the left side of the road. $\endgroup$ Commented Jun 21, 2019 at 19:16
  • $\begingroup$ @Randal'Thor seems like A hasn't paid attention to geography class either :) $\endgroup$
    – Chess960
    Commented Jun 21, 2019 at 19:31

2 Answers 2


You haven't been paying attention in

Organic chemistry

Because you forgot about

Chirality. Many molecules that are the building blocks of life, like amino acids and sugars, have non-superimposable mirror images - a "left-handed" and "right-handed" version. On earth, amino acids are "left-handed" versions of these molecules, and cannot be swapped for the "right-handed" version. Similarly, sugars are "right-handed", and the body is unable to process sugars that are "left-handed". When you go to the mirror universe, your body will be unable to process these molecules of different chirality, so you will be unable to survive indefinitely.

During your brief visit to the mirror world, though, you may be amused by the oranges that smell like lemons and the spearmint that smells like caraway. Don't take mirror ibuprofen for a headache, though, since it'll be totally inactive in your body!

  • $\begingroup$ I don't actually know - is this accurate? The issue arises in the context of a LH item in a RH overall body, so to speak - but if * everything * is reversed, would it be a problem? $\endgroup$
    – Stilez
    Commented Jun 22, 2019 at 4:11
  • $\begingroup$ @Stilez I don't think you become "flipped" upon traveling to the mirror world, which is where the mismatch arises. $\endgroup$ Commented Jun 24, 2019 at 2:14
  • $\begingroup$ I took my lead from the question, which described the entire universe as mirrored. If its mirrored at the level of chirality, then * all * chirality will be mirrored, hence the question whether an issue exists. (If chirality isnt mirrored, and only the macro level is mirrored, then individual molecules/proteins will stjll have the original handedness, so the situation you're describing won't exist by definition). $\endgroup$
    – Stilez
    Commented Jun 24, 2019 at 4:49

I think the problem is

I haven’t been paying attention in physics class because I’m right-handed and my mirror is left-handed.


Become ambidextrous?

I also have

Scars and other birthmarks that aren’t symmetric — a scar over my left eye becomes a scar over my mirror’s right eye.

  • $\begingroup$ Or you haven't been paying attention in English class, because all of the road signs would be mirrored and unreadable. $\endgroup$
    – Duck
    Commented Jun 21, 2019 at 19:02
  • $\begingroup$ "What makes the story interesting," says A. "Is that it would revolve around your struggle around living in the mirrored world, reading the signs, covering your scars, learning to write left handed and so on." "No," said B, "that's still impossible because ______" $\endgroup$
    – Chess960
    Commented Jun 21, 2019 at 19:04

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