My question regards mirroring, specifically what you would expect from a universe that was mirrored from the perspective of our own, regarding its interactions with our own. The mirroring works exactly, well like a mirror, so handedness is going to be switched it seems on many things.

The universe in question is identical in all other respects, but is mirrored. I suspect there would be significant changes, but these wouldn't affect the world itself somewhat like a anti-matter universe, but if the two worlds interacted, say through a portal or something it would affect their interactions potentially violently.

Certain things come to mind right away: many organic compounds have a handedness, and as thus you can't consume them (differing handedness is how some fake sugars work), however more importantly I fear having opposite handedness on the subatomic level might mean any interactions between the two worlds would be very violent. I need to know the effects of interactions between "mirrored" universes for a future question, but if any interactions between the universes resulted in some catastrophic effect that would rule out this specific scenario.

Other than the potential for destructive interaction, merely having people not be able to eat the other universes food doesn't bother me, only results which rule out travel between universes bother me. Ultimately I ask this question, because I simply don't know enough to say how opposite handedness (or whatever you expect with mirroring) would affect the interactions between otherwise nearly identical universes. An ideal answer tackles the subatomic aspects, and if the interactions aren't to destructive then it also tackles some other effects at higher levels like chemistry.

Clarification The only difference between this universe and our own is is that it is flipped back to front exactly like a mirror, as thus the only difference effects will occur when you travel between them.

  • $\begingroup$ I don't think this question can really be answered as there are many different forms of "handidness". Everything from humans favoured hands to the spin of sub atomic particles. In other words you need to be more specific as to exactly what is and is not mirrored in this universe. $\endgroup$
    – Tim B
    Aug 11, 2015 at 20:36
  • $\begingroup$ @TimB Ok I hope I cleared up exactly what I mean I mean everything is flipped essentially. $\endgroup$ Aug 12, 2015 at 2:50
  • $\begingroup$ This immediately came to mind. i.imgur.com/FLBiOZv.jpg $\endgroup$ Apr 4, 2016 at 19:06

3 Answers 3


Let me elaborate with some specific examples.

If you arrange copper, nickle, salt (sodium, chlorine) water (hydrogen, oxygen) according to plan and construct a device that produces electric current (dissimilar metals make a battery), make a coil of wire to form an electromagnet, coax more electrons out of the wire to fly across the magnet, which way will the path of the electrons bend?

If you reversed all, the directions when you built it: which way did you coil the wire, how are the components arranged on the bench, how did you label the ends; then the entire experiment will be a mirror image, including the resting path. Make a movie of the experiment, show it normal and show it mirrored, and both are correct in this universe.

So if you reverse left and right everywhere then nothing changes regarding gravity, electromagnetism, or the strong nuclear force. Only processes involving the weak "force" will make any difference.

So what's the point in your story? If everything is the same, why mention it? We presume it will be something people will notice. If you could travel with your apparatus, or at least a physical model that lets you say "this is left" along with the directions, and the electrons bent the wrong way, that would be consistent with the laws of physics if the charge of the electrons were reversed... oh, but the electromagnet would flip polarity also, so it still comes out the same!

You basically can't arbitrarily say some things are mirrored, since everything follows interrelated rules.

So you need to be more specific as to what is changed. If "everything" then it's nothing, which is pointless.

If you just pick things, without much knowledge of physics, you'll probably keep finding that it can't work.

So... look only at things that are conditions, not laws. Like, a planet with life based on mirror image molecules. But that doesn't need a different universe.

Your actual point is "everything the same... only notice a problem where they meet" and antimatter is a good way to go. Reversed time might amount to the identical thing if the time arrows line up across the portal.

  • $\begingroup$ Hmm looking back at this question one problem that had occurred to me right away, is that i'm not sure whether antimatter really is identical except for being opposite chirality. Honestly i'm not even sure how chirality flipping would even work given all the weird quantum stuff, hell I'd like someone to try to explain why 1/2 spin particles seemingly have non-euclidean geometry. $\endgroup$ Apr 4, 2016 at 11:09
  • $\begingroup$ Google The Reason for Antiparticles by Feynman. Other than the little book I have, I see there are videos! Feynman can explain the 1/2 spin thing too using the "belt trick". $\endgroup$
    – JDługosz
    Apr 4, 2016 at 14:05
  • $\begingroup$ Yes, anti-particles must exist and are exactly time-reversed. Reversing T is the same as reversing C and P. CPT symmetry is rock-bottom fundimental, like all directions being the same in space. $\endgroup$
    – JDługosz
    Apr 4, 2016 at 14:07
  • $\begingroup$ Huh well what does that mean when you're flipping spacial chirality but not temporal chirality. $\endgroup$ Apr 4, 2016 at 14:29
  • $\begingroup$ Spacial chirality only: 3rd and 4th paragraphs of the Answer. Except for the "weak" force, nothing is different. $\endgroup$
    – JDługosz
    Apr 4, 2016 at 15:12

The combined CPT parity is fundimental. If you reverse P, you also reverse the combined CT. You can do that by reversing C, in which case you have antimatter. Actually, their antimatter is regular matter, since the things that caused the universe to produce matter rather than equal parts will have been reversed.

Or you can reverse T. The flow of time is the other way, but you are caught up in the flow so how can you tell? How do you compare the directions in different universes?

So someone who is transported there via a wormhole that lets a body move unchanged between them:

  1. Will be made of antimatter relative to the surrounding material. Oops.
  2. The mouth will discharge in the local time direction, so it is not obseevable that it's the other way around.

In the latter case, how can the law change but still allow a wormhole to connect the two spaces? You could not come through intact I would think. All the molecules would be messed up. If you did manage it, you would perceive that either the right-hand-rule is changed or all the particles innyour body have had their charges reversed.

Try looking at precession of a gyroscope... that doesn't make sense to reverse since it follows from Newton's laws which don't have directions mentioned in the laws.

  • $\begingroup$ I never said the direction of time was affected, so I'm not exactly sure what you're saying about that. As for antimatter, is it really only different from normal matter in its spin? The only actual difference between universes is things are flipped back to front like a mirror. $\endgroup$ Aug 11, 2015 at 19:56
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    $\begingroup$ @VakusDrake You were looking at fundamental subatomic properties. JD points out one of them, pointing out that if you change one by entering your mirror world, you have to change one of the others to maintain "life as we know it." Reversing the direction of the time axis is one such way you can resolve that pattern. Changing matter to antimatter is another. $\endgroup$
    – Cort Ammon
    Aug 11, 2015 at 20:57
  • $\begingroup$ "the only actual difference" being that it doesn't follow the rules you get if you crunch the numbers? That means you changed those rules too, so it's not "only one difference". And you have to make it all work again. $\endgroup$
    – JDługosz
    Aug 11, 2015 at 21:50
  • $\begingroup$ Re spin of antimatter: Antimatter, pair production, and annihilation must exist due to spacetime symmetry. The anti particle is the same as a time-reversed particle, and any conserved properties will be opposite so they sum to zero. In the case where spin direction matters (e.g. neutrinos), it will also be opposite. For electrons etc. they are produced as mirror images, but the spin of each one can change as it goes through the world. Note that the opposite charge means it will respond to electromagnitism in the opposite direction, all else being equal. $\endgroup$
    – JDługosz
    Aug 11, 2015 at 21:51
  • $\begingroup$ I think in order to understand what I wrote and not get derailed, you need to read up on "CPT symmetry". The P refers to mirror image, and that is in the family group with C (charge) and T (time). If you flip one, you flip another to make the result come out the same. $\endgroup$
    – JDługosz
    Aug 11, 2015 at 21:52

I'd say anything would be pretty much the same.

At a chemistry level, let's say in "normal world" you have "Sugar R", which is ok, and "Sugar L", which is toxic. In reverse world, everyone would go for "Sugar L", because your own molecules would also be the other way around, so you could consume it [citation needed]. Now, if you were a traveler from the "normal" world, you would keep away for their "normal sugar (R)" and go consume the toxic (for them) one, which is the appropiate for it.

At an artistic level could be some differences. Pick a painting, mirror it. Some won't change much. Some will be horrible. So the art (use of perspective and such) could change. How much does art influence the world? Well, that's up to you. I'd say moderately. It could also be argued that mirrored brains made of mirrored molecules would perceive the mirrored version as more artistically pleasing so... who knows?

But yeah, apart from some quirks here and there (because of butterfly effect of little instances where the perspective DID matter), I'd say the world would be pretty much the same...

Source: The Legend of Zelda: Twilight Princess.

Its Wii version is a mirrored version of the Gamecube version because Link is left handed and people are most likely to be right handed and that's relevant when using a Wiimote and god forbid we only mirror the character f**k we are mirroring THE ENTIRE WORLD and deal with it, walkthoughs. (Should be noted that, as stated before, some zones look/feel weird in the Wii version because they were designed to be seen and navigated the other way around)

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    $\begingroup$ Yes the mirrored world would be exactly the same as ours to the people in it, however i'm looking more for the effects in terms of what happens when the two worlds intersect. $\endgroup$ Apr 4, 2016 at 13:24
  • $\begingroup$ Well, it depends. If you put the GameCube version in the Wii it has a compatibility mode so it runs ok, but the Wii disc doesn't even fit in the GameCube... in a less "literal" way, I guess the consequences would range from "absolutely nothing" to "instant universal obliteration". Since there are no consequences I can think of, I see it as one of those sci-fi thing that's up to the writer. What would make the story more interesting? $\endgroup$
    – xDaizu
    Apr 4, 2016 at 14:25
  • $\begingroup$ Well there's certainly chemistry implication, you couldn't eat food from the other world, but there would probably also be implications in terms of the interactions at the subatomic level but I don't know what. $\endgroup$ Apr 4, 2016 at 14:27
  • $\begingroup$ You can't eat food from the other world if their mirrored version in our world is toxic. I mean, I'm sure there are plenty of "food molecules" that are either symmetric or both versions are edible, so you can stuff yourself of that in the mirrored world. You wouldn't starve :) $\endgroup$
    – xDaizu
    Apr 4, 2016 at 14:32
  • $\begingroup$ Yeah certain artificial sugars rely on having different handedness, and as a result we can't process them. A substantial amount of chemistry has handedness and would be inedible. Worse is the fact that handedness is really important in some stuff in quantum physics and stuff and while I don't know how it would react it would probably not be good. $\endgroup$ Apr 4, 2016 at 14:38

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