Yay! We figured out how to talk. Oh crap, you're boring. And we're stuck in a room.

December 2, 2007 1:13 AM

Could you and your identical twin from a parallel universe actually hold a back-and-forth conversation in a perfectly symmetric room, or would you just talk over each other for eternity? (Assume quantum theory is bullshit)

This question has plagued me for years. Please assume that "randomness" in physics is only an illusion, or, if you like, that the same random occurrences are recreated on the opposite side of the room.

So imagine two perfectly parallel universes. You and your twin are teleported into a perfectly symmetric room (down to the very particles of matter). So everything you see, your twin sees in the same way. You may assume any object exists in the room as long as it doesn't violate symmetry or non-randomness.

Could you ever have a conversation with yourself? I can't for the life of me think of a way. For example, you can't flip a coin since you'll both say "heads". I've heard a number of compelling arguments, but they've all turned out incorrect. Including a good one involving spin-the-bottle.

Please, tell me how to do this in case it happens to me. Oh, and tell my twin too.

posted by TimeTravelSpeed to science & nature (32 comments total)

Oh, and if you each flip a different coin, you'll both flip it the same way, and they'll both end up landing on the same side. (Assuming no randomness and symmetry)
posted by TimeTravelSpeed at 1:25 AM on December 2, 2007

Assume quantum theory is bullshit

Why?
posted by Blazecock Pileon at 1:32 AM on December 2, 2007

Begging the question?
posted by finite at 1:48 AM on December 2, 2007

FUHlagged as BBQ.
posted by Ambrosia Voyeur at 1:53 AM on December 2, 2007 [1 favorite]

Even if you could, you shouldn't, because it breaks the guidelines.
posted by grouse at 1:55 AM on December 2, 2007 [2 favorites]

Could you and your identical twin from a parallel universe actually hold a back-and-forth conversation in a perfectly symmetric room, or would you just talk over each other for eternity? (Assume quantum theory is bullshit)

This question has plagued me for years. Please assume that "randomness" in physics is only an illusion, or, if you like, that the same random occurrences are recreated on the opposite side of the room.

So imagine two perfectly parallel universes. You and your twin are teleported into a perfectly symmetric room (down to the very particles of matter). So everything you see, your twin sees in the same way. You may assume any object exists in the room as long as it doesn't violate symmetry or non-randomness.

Could you ever have a conversation with yourself? I can't for the life of me think of a way. For example, you can't flip a coin since you'll both say "heads". I've heard a number of compelling arguments, but they've all turned out incorrect. Including a good one involving spin-the-bottle.

Please, tell me how to do this in case it happens to me. Oh, and tell my twin too.
posted by equalpants at 1:59 AM on December 2, 2007 [8 favorites]

There's breaking the guidelines, and then there's Breaking the Guidelines. I'm pretty sure you're doing both here.
posted by jjg at 2:00 AM on December 2, 2007

(Sorry, couldn't resist! But just in case this doesn't get deleted, I'll actually answer the question, too...)

I'm gonna say no. If you're assuming that the twins have identical states when they appear, that the universe is deterministic, and that nothing can break the symmetry, then they'll have identical states forever. Whether or not you can have a "conversation" with someone who always says, hears, and thinks exactly the same thing as you depends on your definition of "conversation", I guess; I'd say no.
posted by equalpants at 2:02 AM on December 2, 2007

So everything you see, your twin sees in the same way.

Then how would you see each other?
posted by amyms at 2:04 AM on December 2, 2007

Yes. Okay, the first problem is that you will believe that the other person you are seeing is you basically. The person mirrors everything you do exactly, so you would think it were you. However, IF you were prepped before hand that the thing you see in there is someone completely different, then you can figure out how to talk. You know why? Because of free will. Because of the ability our brain has to randomize perfectly symmetrical experiences.

So, I thought about this, and what would _I_ do to my twin. Now remember, my twin is thinking exactly the same thoughts I am. Let's go through our thought train.

Both: Hello
Both: We have to break out of the sameness loop for just one moment and then we will have differing experiences, in effect splitting our past experiences, and allowing us to have independent souls
Both: So, to do so, you bend downwards, and I bend upwards.

_At this point, both twins will do exactly the same actions, either up or down_

Both: Oh crap, we did the same thing.
Both: Let us write out the digits of pi on this piece of paper
Both: Okay, what we do is that we will both pick up this stone. Then we walk in a circle clockwise

_Both walk, and end up on oposite sides of the room_

Both: Throw the stone up, and because of the different gravitational forces in the different parts of the room, the stones will land on different digits of pi. We will walk that amount of steps backwards. Then we will break this symmetry between us.
Me Nmbr 1: Yeah, we did it
Me Nmbr 2: Oh yeah we did it!
posted by markovich at 2:34 AM on December 2, 2007 [4 favorites]

Well, what if the twins are by nature prone to Devil's advocacy, they expect moments of profound irregularity, and they tend to talk to themselves anyway? You might end up with a person who is completely comfortable with yakking away at him/herself.
You didn't ask whether the conversation would be dull and painfully, eternally self referential. Hell might be other people, but hell with your parallel universe twin would be MetaHell. Talk about your tedious flameouts.
posted by maryh at 2:45 AM on December 2, 2007 [1 favorite]

You have described a glorified mirror.
posted by contraption at 3:12 AM on December 2, 2007 [3 favorites]

markovich: if everything is posited as symmetrical, I don't see how you can get different gravitational forces.
posted by creasy boy at 3:31 AM on December 2, 2007

If it is mirror like symmetry where left and right are reversed for your twin and you, it would be easy because you could just point to one wall and say that wall is north, then you have a point of reference from which to break the symmetry. For example you could say whoever is in the east will talk first.

If left and right are not reversed it is more difficult because you could never even point to the same wall. You couldn't write PI on a piece of paper together because you couldn't agree on where to start writing. This is the problem with spinning the bottle, you could not get an unsymmetrical bottle into the room if left and right are not reversed. (I'm sure there is a mathematical term for this kind of symmetry, chiral symmetry maybe).

In this case I'm not sure how you would break the symmetry, maybe using octonions or lie groups, but my math isn't close to being good enough to figuring this out.

I don't see how this breaks the guidelines, it is a pretty straightforward geometry problem and has a clear answer. Either there is a way to break the symmetry or not. I'm very curious to see if someone smarter than me can shine some light on this.
posted by afu at 3:44 AM on December 2, 2007

There will be different gravitational forces because if both are looking at each other, and then both move clockwise, they will move in opposite directions to opposite sides of the room. On opposite sides of the room, gravity will be different.
posted by markovich at 4:05 AM on December 2, 2007

afu: This falls pretty firmly into the made up "what if" science questions which are not allowed, especially since it is premised on several ideas contrary to fact.
posted by grouse at 5:26 AM on December 2, 2007 [1 favorite]

I agree with equalpants. I've always wondered a similar thing, (mine was how to cross a narrow bridge at the same time), but outside of "perfect symmetry". I've always just resolved it by assuming both of I would agree that whoever is closest to some object would go first. With your scenario I'm both the same distance from everything, and if the system is closed it's, as pants said, completely deterministic. However, if the system isn't completely closed, then you could agree that whoever sees the first star out the window, for example, goes first.

All in all, it would be a pretty boring conversation. I think you should just wrestle.
posted by monkeymadness at 5:37 AM on December 2, 2007

grouse: It's a geometry question, though maybe it's not worded the best. People ask about math questions here all the time. The question has a definite answer and that to me is the gold standard for if a question is should stay or not.
posted by afu at 5:37 AM on December 2, 2007

In a very complicated and detailed scenario that I invented, full of arbitrary rules that break some laws of physics but ignore others, and by following very specific guidelines that I am making up out of my own daydreams, can a certain scenario take place?

Dude, your thought experiment sounds like Dungeons and Dragons.

No, you can't stone a golem. Obviously.
posted by rokusan at 5:43 AM on December 2, 2007 [3 favorites]

Assume quantum theory is bullshit

Okay - one possibility would cause your other self to die some time after entering the room, in addition to being a few centermeters tall. Under conventional models of the universe, your other self would have to come from a universe that wouldn't jeopardize the integrity of our own. One such realm would be a -Ɲ continuum, which would be smaller and shorter-lived than ours. For you and your doppleganger to see your "selves", the space between the rooms would have to be magnified accordingly, with varying gravitational ratios. A drawback of the reduced scale of your counterpart's universe would be the shorter energy cycle. You² (or rather, You²-Ɲ) would have a lifespan equivalent to a housefly, at the longest.
posted by Smart Dalek at 5:48 AM on December 2, 2007

You know who else came up with crazy "what if" scenarios?
posted by afu at 5:53 AM on December 2, 2007

It's a geometry question, though maybe it's not worded the best.

Perhaps you would like to reword it before the deletion hammer falls? Because I am having a really hard time seeing this as a geometry question.

You know who else came up with crazy "what if" scenarios?

I guess you should be looking for the next Einstein on BBQ instead of AskMe.
posted by grouse at 5:58 AM on December 2, 2007 [1 favorite]

Maybe I'm missing something, but this strikes me as a really easy question to answer. If you start two identical (down to the molecular/quantum level) machines in identical (down to the molecular/quantum level) environments, they'd run identically (given a deterministic universe).

The only ways to break the unity would be to (a) vary some detail between the machines. Either make some part(s) of one machine different from their counterparts in the other, or vary their environments. Even tiny variations should be enough to change behavior (unless those variations happen in sub-systems and have exactly the same effects is the higher systems that matter).

Or (b) you can assume that people are not machines, by which you can grant each person some sort of supernatural aspect, like a soul, which is, by definition, unique.

By the way, I think there's a cleaner way of expressing your problem. Don't bring the twins into the same room. Instead, put them in two different -- but completely identical -- rooms. That way, the twins can be in exactly the same positions, relative to objects in their rooms.

Put a loud speaker and mic in each room so that they can talk to each other. Given my assumptions, above, they will always say the same thing at the same time.
posted by grumblebee at 6:20 AM on December 2, 2007

It's not just a geometry question. That's why you can't just point to one corner and call that north; both would point in the same direction (i.e. in different corners) at the same time. A deterministic universe is assumed, including determination of the human mind, and the two people have identical psychology, identical neurons, and find themselves in the identical situation.
posted by creasy boy at 6:22 AM on December 2, 2007

And yeah, this question is against the guidelines and sounds like what BBQ is intended for.
posted by creasy boy at 6:23 AM on December 2, 2007

On opposite sides of the room, gravity will be different.

The question presupposes absolute symmetry. That's a good part of what makes it hypothetical.
posted by creasy boy at 6:25 AM on December 2, 2007

In a very complicated and detailed scenario that I invented, full of arbitrary rules that break some laws of physics but ignore others, and by following very specific guidelines that I am making up out of my own daydreams, can a certain scenario take place?

I disagree. Some questions involve fictions that -- because they are fictions -- could have infinite outcomes. An example: "if 'King Lear' had a sequel, what would happen in it?" Such a question is unanswerable, except with chatfilter.

On the other hand, it's reasonable to ask, "If there was no gravity on Earth, what would happen if I released a ping-pong ball from my hand?" There IS gravity on Earth and there can't NOT be gravity on Earth. So this question's scenario could never happen. Still, the question is answerable.

TimeTravelSpeed's question is more complicated, but similar in that he has crafted a fictional -- but bounded -- scenario.

There are many questions on AskMe that are set in fictional worlds, but we don't notice this, because the fictions are banal. For example, "My girlfriend loves big band music. What would make her happy on her birthday?" Her birthday hasn't happened yet, but the question asks us to craft a fictional world in which it has. It's a bounded world, so that's pretty easy to do. No one says, "Dude, her birthday isn't until next week. By then, ANYTHING could have happened. Your girlfriend could be dead!"
posted by grumblebee at 6:32 AM on December 2, 2007 [1 favorite]

Grumblebee, there is a difference between a situation that hasn't happened yet (anticipating facts) and one that cannot happen (a question contrary to fact). This question is the latter, which is more like "My girlfriend loves big band music and was born on 8 August. What if she were born on 8 September instead; do you think she would still love big band music?"
posted by grouse at 6:42 AM on December 2, 2007 [3 favorites]

Well, we really should be discussing these concerns here.
posted by grumblebee at 6:45 AM on December 2, 2007

The symmetry is assumed between the two opposing worlds, and not within a world.
posted by markovich at 6:55 AM on December 2, 2007

markovich: I believe the question actually is assuming symmetry within a world (see the poster's first comment). I think the bit about two parallel universes is just there to imply that the twins have identical mental states when they enter the room.
posted by equalpants at 7:15 AM on December 2, 2007

This actually happened to me once. I and my twin started off talking over each other, and it was very frustrating. We started running around the room shouting and bouncing off of the walls. A little chaos theory later, and we had enough differences to have a chat, but it turns out that conversations with your transdimensional twin are awkward.
posted by ROU_Xenophobe at 7:24 AM on December 2, 2007 [1 favorite]