Friday, September 17, 2010

Other Universes And Why We Probably Aren't In Them

Family Guy is owned by FOX. Also, the
episode this is from was pretty good.
Parallel universes are a fun science fiction trope. Imagine a world similar to our own where things are very similar but different. Universes where someone else won that one big war, or dragons roam the Earth, or the Star Wars prequels kicked ass. And in these universes, there are various versions of yourself, identical, yet different.

Except that last part is illogical.

Before I continue, I want to make a few things clear. This hypothesis is based on cause and effect, probability, and biology. For all I know, fate is a real thing, and if some all powerful being wants The Daily Show With Jon Stewart to be a constant in the multiverse, then yes, Jon Stewart will exist in all continuities regardless of anything I'm about to say.

Given that we can neither prove nor disprove things such as fate and destiny, however, that is not being considered here and is a different debate altogether.

For the purpose of this argument, the definition of a dimensional alternate is "someone born with identical DNA". It doesn't matter if they mutate later or whatever; so long as they're born with DNA identical to someone in another universe, they're someone's alternate. This ignore's any spiritual or other technical ways one could arguably be an alternate.

Odds of Someone's Parents Meeting

There are so many factors involved here that I honestly don't know how to calculate it. I don't think anyone could. The odds of two specific people getting together in one universe are low enough, but in more than one universe with different histories?

Consider one of my examples where something is crazily different, and the Star Wars prequels KICKED ASS! But what if two people met and fell in love over the internet as a result of their mutual hatred for the prequels? In a universe where there was nothing to complain about, would they still get together, let alone know that the other person even exists?

It's a silly example, but consider any "how did you meet" story, and you can find points where you could have prevented them from meeting by changing just one little thing. Now consider a universe where America lost the Revolutionary war. Imagine how many "little things" that would change.

Again, this argument doesn't factor in fate, the force, cupid, etc, so don't comment with "true wuv" or, well.... I guess I'd just sit at the computer and look annoyed. Not much else I could do, really.

Odds of a Specific Person Being Born

Let's say that in spite of President Lincoln being a space dingo democrat in this other universe, one's parents still meet and have children. The odds of one's dimensional alternate being born remains low all the same.

Remember, for the sake of this discussion, one is not a dimensional alternate unless they have identicial DNA. I don't want to get too graphic here, but if you think about it, it's much more likely that the equivalent of a fraternal twin or a sibling would be born than a dimensional alternate with identical DNA. Whether the first X chromosome is identical would depend on when the baby was conceived, and the second X or Y chromosome would have a low probability of being identical regardless of when conception took place.

This is a problem with time travel as well. I know the universe was pretty easy going in Back To The Future, but I still think Marty should've shapeshifted some as he messed with continuity. Heck, he could've even wound up changing genders!


To the fan art machine!

Exponentially Complicated

When you consider the various reasons two people might not meet and the odds against a specific person being born, the odds of one person existing in multiple universes is pretty low. Thing is, that's just one generation. This applies to every single previous generation.

As such, not only are the odds of one specific person being born astronomically low, but the odds of their parents, grandparents, etc. were low, too. The odds of the family tree being multiversally constant becomes exponentially lower with each successive generation.

Actually, I shouldn't say every previous generation. It's really just up to the point where the universes were last identical. For another universe to be recognizable at all as parallel, it seems like it would have to identical up to a point in history.

Let's say Marty's reckless time travel resulted in the universe diverging into two separate universes, meaning the universes are identical up to sometime in the 1950's. Eventually, the ripple effect of the changes to Hill Valley would be far-reaching, but initially, that town would be the only place with significant changes. By the 1980s, the odds of the latest generation of Hill Valleyans being identical in both universes would be pretty low.


My conclusion is thus: Short of some outside force manipulating who is and isn't born in each universe, the odds of a single person existing in multiple universes where events were different prior to their birth are low to the point of essentially being non-existent.

As such, in a hypothetical universe where things are left to chance and, for example, America lost the revolutionary war, none of us would logically exist.

In spite of all this, the concept is fun enough that I am willing to ignore it, work around it, whatever I've gotta do to be able to write and enjoy parallel universe stories. Yes, there are logical flaws, but science doesn't run the show when it comes to fiction.


  1. On the nose. Parallel universes are fun, but logic has to go on the back shelf whenever they get used in a story. Seriously, it's the "stepping on an ant" thing raised to the power of 'lots'.

    Loving EGS, btw. I found it sometime around the "Grace's Party" storyline and have been a regular reader ever since.

  2. Your point is solid, but only applies to a certain subset of multiverse fiction. Specifically, those where a) there is not fate or any narrative causality at work, b) the branch point is explicitly before your birth, and c) there are a finite number of universes.

    Terry Pratchet's "Night Watch" had an excellent quote this discussion reminded me of:
    "Alright, he's been sent back in time, and we get that. But now he's taken on the role of his old mentor, and through a series of increasingly contrived coincidences, come to look very much like that mentor. Now you tell me - is that the historical imperetive, or is that narrative causality, or is that just plain weird?"

  3. "When you consider the various reasons two people might not meet and the odds against a specific person being born, the odds of one person existing in multiple universes is pretty low."

    I'll grant you that fact when it's time travel creating multiple universes, but most universe hoping sci-fi I've seen operate off of the theory that there is literally an infinite amount of universes making up every possibly combination of circumstances using our laws of physics. as such no matter how low the chances of you existing in a specific universe with how big the multie-verse is there will be an infinite number of your alternates living in worlds were say the social norm is to walk sideways. mathematically they may be "less" frequent then those universes were you don't' exist, but an infinite amount of alternates is still infinite.

    and from there you just rely on story convince to take them to a world with an alternate. n

    wow I think I just level up my nerd in that post :P

  4. The thing about odds is that they matter less and less the closer we get to infinity, and the base assumption for alternate universe fiction is an infinite number of alternate universes. Arthur C. Clarke's "The Other Tiger" has fun with some of the implications here.

    Hmm... There seems to be some ninjaing at work here. May as well build off it: the odds of ending up in a universe that contains one of your alternates are a bit of a problem, but narrative causality comes into play there.

    Gah, double ninjaed! At least I've got the Clarke reference.

  5. Interesting. I agree with venatus's point (that there is an infinite amount of alternates). Basically, the reason why you keep on meeting alternates is that your multiverse-exploring device actively tries to send you in universes where such occurrences are possible. If you don't exist in an universe, your device will actively try to prevent you from getting there.
    Makes one wonder how the device works.

    Incidentally, I've been working on a Multiverse project for close to a year by now. My basic conclusion is that one has to define what can "generate" a new universe to properly understand how rare or frequent alternates can be.

    In my system, the multiverse has a limited "meta-volume", and universes take "space" in this volume. Universes can be infinitely small (thus ensuring that there still is an infinite amount of universes), but small universes have a very short life expectancy - they get eaten by bigger universes. That event's called a Verse Necrosis (Verse = universe).
    On the opposite, you've got Verse Genesis, which is when an universe is "asked a question". What is or isn't a question depends largely on context, but the larger the universe, the more important the question must be (in most "stable" universes, questions usually involve over twelve human lives).
    When such a question arises, the universe splits in two or more universes (one per different answer to the question).

    Since big universes need big questions to perform Verse Genesis, they usually ARE pretty similar for a few years after the split - most of the time, the Butterfly Effect needs a few decades to actually kick in.

    This system was eventually corrupted when people realized it was perfectly possible to hijack Verse Genesis and Verse Necrosis to create new universes, but there are only a handful of these so the rules are globally coherent.

  6. Then again, having parallel universes means (usually) that you have infinite tries to get the formula right with the correct small changes, so it all kinda works out in the end.

    Now the problem is figuring out how the worlds are ordered, IOW do similar worlds share a lower proximity than those with bigger differences? If the proximity is subjective, or if there is no concept of proximity to begin with and the whole thing depends on a key detail to begin with, that's a whole different ball game.

  7. Most parallel worlds are supposed to be part of an infinite variety of worlds. In infinity everything possible exists. So while the odds are minuscule they have to happen if you give it infinity time-space. And so most of the earths mentioned in comic books and tv and so on gives a false impression because you go to the boring earths were you were born but grew up differently, instead of the interesting one where the beetlemen rule and the gravitational constant is seven.

    Or crazier stuff than that. That's the thing about infinity, it all happens somewhere.

  8. Okay, but what about this:
    The universes that we can travel to are ones that branch off of ours (or ours branched off theirs; it doesn't make a difference) relatively recently. Branching would be defined as someone doing something (anything) different from what they did in our universe. Therefore, there hasn't been time for those huge changes to take place.

    Using one of your examples, if America lost the revolutionary war, it is a branch that happened much too long ago for us to reach a universe like that. Not that I entirely disagree with you, I just think that there are still ways to make it work.

    Your arguments still make most multiverse stories sucky science fiction and you super smart.

  9. Truthfully, I think your point is fairly valid for high enough degrees of divergence. But through random confluence of events you can conceivably arrive at "Key Points" where- by hysterically unlikely coincidence or else by past alterations of fairly insiginificant degree- such as a minor alteration in the flavor of tapioca pudding and the genetic dominance of four leafed clovers over three leafed breeds- you can have a superficially (and in all significant and important points) identical world with a widely differing history and minor details. While the divergence for genetic conditions might have its roots millions of years in the past, and the recipe for tapioca pudding might have branched off several hundred years ago, you can still have a more or less identical world that suddenly branches off... Now.
    But whatever. You can think of the multiverse as a tapestry in multiple directions, where each direction charts out a range of possibilities. Where certain events are more likely in a single universe branch off the multiverse, the "distance" travelled between them is both smaller and simpler to traverse. Therefore, when comparing a subset of disparate universes, the easiest and most accessible universes to travel to would be the ones where gross details- such as a person's existance- would be highly convergent or else with a very recent causal branch off, meaning the point of divergence between two compared universes would be fairly recent. In this fashion you could say that by convergence of odd effects to produce the same general results it would be more likely to hop universes to where you exist and Star wars 1 flopped, than to jump to one where you DON'T exist and Star Wars flopped. That I believe is the hidden variable and mechanic behind universe hopping as written by various sci fi writers. Think of it as potentialities, where your current state of existance is the one with the highest potentiality for your phase signature, whilst jumping to other universes with a similar potentiality is like walking up a gentle slope. On the other hand, accidentally hopping into a universe where you don't exist is kind of like accidentally falling to a cliff ledge three stories up- doesn't tend to happen without a high energy event, deliberate intent, or a really strange set of oddball occurances.
    A question, then, propsed by my best friend peering over my shoulder as I write this: If, in another nearby universe, where you exist and this blog entry does not, is that universe version of you less or more intelligent?

  10. Since others above covered it quite well, I will just reiterate the biggest reason this entire post is wrong:

    Obsidian Dice said:
    "Your point is solid, but only applies to a certain subset of multiverse fiction. Specifically, those where a) there is not fate or any narrative causality at work, b) the branch point is explicitly before your birth, and c) there are a finite number of universes."

    Thanks OD, for ninja'ing my point entirely, heh.

  11. Objection: While it is true that the chance of a particular person existing in multiple universes is infenitesimal, there are a near-infinite number of them! There are many, many more universes than there are combinations of DNA, which is itself 4^(k*100000), that is, four bases to the ppower of a number in the hundreds of thousands that I currently forget. This is because, if the parallel-univers theory is correct, then a new universe splits off every time any atom in the universe vibrates differently.

    So, it's entirely possible to find a universe where things are radically different, but you would still be the same. Heck, El Goonish Shive probably exists somewhere out there.

    Given this, then, is it so hard to believe that, in a universe with FTL travel, transporter beams, and replicators, it is possible to pick and choose your parallel universes?

    "All myths are real, all songs are true..."

  12. ... And I just noticed I was ninja'd umpteen times. So Yeah.

  13. The horrible quantum ninjas have struck so many times that I cannot possibly post something on topic without repeating some one. Bob was there too.

  14. Awesome post, but I wanna make a slight counterpoint to your Back to the Future comment.

    If anything, the story was largely cynical about how big an impact most people have. That the entire cast of characters were such middle of the road, minor middle class peeps (even after Marty's father became a decent Sci-Fi writer) that his simple meddling with a few people's lives really had no major effect outside his own circle.

    Really, his meddling was pretty the first one he was doing his best to "reset" the original continuum...and only served to give his daddy balls (which actually, within his little circle, made a large difference).

    The one time that a major change was made to the timeline, it had major elevating Biff to a local power, the entire landscape of Hill Valley was drastically changed (and who knows...outside of hill valley may have changed as well, it was just outside the scope of the story).

  15. The one that had me screaming the most was an episode of Sliders in which instead of so much oil being under the middle east, most of it was under the US.

    But people and civilization and so on, other than where all the oil was coming from, still happened roughly similarly. GAAAH!!! An earth with what amounts to a somewhat _DIFFERENT_ _GEOLOGICAL_ _HISTORY_, still managed to produce humans, and not only that, english speaking humans, etc etc? I repeat: the difference was far enough back that effectively geology was different, yet still you have (for the most part), standard human culture.

    Although, the flipside is in one of the episodes, one of the characters actually notices this issue and basically says "You know, all these worlds and there're still versions of us in them. That means There Is A Plan, so that's why I believe in god."

    Well, I guess at least it's nice that they _noticed_ the issue.

    (of course, if you want to get into the actual subject of alternate quantum branches, there's much more too it than "all possible worlds exist". The whole point is that you have a quantum amplitude field flowing over the space of all possible configurations and... actually, this would be a long discussion. :))

  16. Tough talk from a guy whose fiction itself revolves around parallel universes with a single constant (Tedd). Methinks the guy who turns guys into ladies doth protest too much.

  17. I'll own up to it right now: I'm the one responsible for the pan-dimensionality of The Daily Show With Jon Stewart. Believe it or not, it is the only thing preventing WWVI. Can't do anything about the next three, but I won't see the Reformed United States of the Americas go down like that.

  18. Drat you people for pre-emptively reading my mind!

    An alternate theory, of course, is that the multiverse is governed by Fixed Points In Time, with branches forming out of and merging at each point. Think of it as a Timey Wimey Multiverse Ball. Obviously, the Daily Show is one of these Fixed Points.

  19. As people have pointed out already, the main flaw of your theory is that it only says that the odds are very low.

    Ok, let's assume the odds are 1 in 10^600, or even worse. In a finite number of universes, those odds would have a meaning, but, if there are 10^600, it becomes almost certain, and with 10^600000, totally certain, multiple times.

    With a infinite number of iterations, everthing that IS possible, IS certain.

    So, if we consider a finite multiverse, you're right. yes, it'd be almost imposible. but if we consider a infinite number of universes? why not? There'd be both infinite number of universes with ADN duplicates of a particular person, and also infinite number without. simple as that.

    The paralel universe theory usually works under the concept of infinite universes, but rarely use it fully, tho. We're rarelly shown more than 2 or 3 verses. This leads to a perceived finite multiverse, where your theory stands ground. but let's not forget that's because of media limitation, or Writers Are Not Scientists.

  20. Several of the series I've seen with alternate universes (although by no means all, or even most) usually start with "nearby" parallel universes - the ones that are most similar, then start to diverge earlier in history as you go further "away". Sliders did this, as did Star Trek at least once (Worf bouncing between universes) (and poooossssiiibllyy Stargate, I'd have to see the SG-1 episode again, although Atlantis arguably did do this)

    As the Star Trek characters continually complain: Temporal mechanics is the worst subject to exist.

  21. I found it fairly self serving as to how you got around this concept in EGS. You added the "unless an outside force intervenes" clause, which was the case for Ellen. I'm not complaining or really even criticizing, just pointing it out.

  22. Consider for a moment that relative multiple dimensional distance is usually considered to be the sole defining factor in cost of energy to travel between Time Line A and Time Line B. The more similarities there are between the two time lines, the more probable it is that they are (in a multidemensional sense) "nearer" to each other than two time lines exceedingly far away from each other. As this is a thought experiment, I will Occam's Razor into place the idea that only the absolute distance between two time lines determines energy requirements rather than there being other systems being required.

    As others have said, infinite universes produce infinite variations of the "you/not you" paradox. While many latch onto the idea that "infinity is weird", my presupposition latches onto the notion that "YOU are weird". What all these multiverse hopping shows would indicate, then, is that personal consciousness is one of the fators that determines the clustering of a branch in the multiverse. As most of these shows tend to portray some variation of "psychic energy", this would actually be supported in most cannons with the implied statement that "psychic energy therefore branches the multiverse". Still, this is rather unsatisfying and leads me to how I've always thought about the problem:

    Time travel is relative. Rather than all universes being equidistant from one another, I would posit that universes are clustered RELATIVE TO WHO TRAVELS THROUGH THEM. The universes I will travel through will permute differently than the universes you travel through. Returning to the psychic energy notion, my psychic imprint would be the base line of travel and thus provide the commonality between all universes I would visit. If a group is traveling, they'd travel through the cluster group that requires the least amount of energy to plow through, which means all of them would be in it in some form or another.

    What this doesn't cover is why people would then arrive in universes where they WEREN'T in existence. At that point, it would be probable that they probably found the equivilent of a resonant frequency in their transmission profile, and were thus able to severly reduce most of the energy costs associated with going off their line. Or maybe there was a crack in space. But at that point, I would probably be forced to say "There is was a Purpose" if they otherwise tend to encounter the universes under discussion.

    None of this would hold sway in a fiction where encountering oneself was a rare ocurrence. Then, it would either be some argument based on harmonics/resonance or a truly random system producing an interesting result in the provided narrative (like picking up a phone RIGHT as a phone call to your number was JUST completed, thus bypassing the ring).

    --Dawson G

  23. Well, Vramos, feel the need to point out that mathematically speaking they've already proven that even in an infinite set, there can be different values of infinity, without either one having a limit.
    Take for instance, the set A{1,2,3...} and compare it to the set B{.5, 1, 1.5, 2,2.5...}.
    While each whole integer in set A has a correspondant in set B- remember, both sets stretch to infinity- This still leaves half of the numbers in set B unaccounted for- as a result, this mathematically means that for all intents and purposes, there are twice as many numbers in set B as there are in set A. Ergo if set B represents all POSSIBLE combinations, while set A represents the LIKELY ones, you still have unlikely ones left over.
    The point being that, even while the concept of infinite means yes, you likely have a perfect counterpart out there, the chances of you running across that counterpart randomly is so hysterically unlikely as to approach zero.
    Unless, as in my previous post to account for the circumstances fictional characters repeatedly find themselves in, there is a natural or artificial means of filtration, such as a divine power, the ability to choose, or the natural tendency of the least amount of circumstantial alteration in universe hopping(i.e. the closest analogs are the easiest to get to). Let's not talk about the umpteen gazillion factors that would make ANY life or recognizable structure/natural laws/ratios null and void- and probably destabilize you into quantum fuzz the moment your ill adapted "Our Universe" designed body popped up in it.
    I remember reading somewhere that in order for our universe's laws and ability to harbor living things to occur, there are something like 200 natural values ranging from half life decay and strong/weak force interactions to the proportional force of gravity and the laziness of electron orbits. Any one of those 200 values is slightly different, no life. Slightly more different- no stars, even no atoms.
    But yeah, if universe hopping happens, there's likely some sort of filter.

  24. You're right, but for the wrong reasons. As nearly everyone else here has said, the multiverse theory that allows for alternate realities holds that every possible variation exists. According to this theory, every time I flip a coin and get heads, two quantum universes result - the one I reside in with heads, an a new one where I got tails. If I roll a d20, I create 20 quantum universes.

    It's a reasonable assumption in such a scenario that whatever allows you to cross into other universes is a similarity to your own universe, such as your own existence, or "nearer" subtle variations such as recent events. And that's why I say your reasons are wrong.

    The reason I say your conclusion is correct is probably clear from my flippant reference to creating universes a moment ago. Matter and energy are constant within a universe, and yet I create an entire universe equal to my own by the mere flip of a coin. Furthermore, this strongly implies that there are multiple universes out there where coins always have landed heads, and still others where it spontaneously became consistent for years at a time, to where the concept of probability doesn't exist in those universes simply because of random chance. These absurd extrapolations not only could, but MUST exist in the quantum multiverse theory.

    Another plot hole is the notion that they always get back to their universe, even if it's through alternate means. Stargate SG1's "mirror" gateway was a great example of this. They tried to re-link based on what rank was on an officer's uniform. In infinite universes, there are an infinite number where that rank is the same. Your chance of finding one close enough to yours to not notice major changes are literally infinitesimal.

  25. Absolutely. I've been trying to articulate the same darned thing to people for years.

  26. I should note that this doesn't take into account the sheer number of alternate universes. Since universes diverge if so much as an electron is in a different place (according to the theory). Therefore, while it is very unlikely that the target exists in many universes, the ridiculous quantity of alternates simply means that the universe in which you are you but have laser eyes does exist. You just have to find it.

  27. I just wanted to say that I love this comic, and the other people who read it. You're all so interesting and funny. :D

  28. My only thought, and I'll keep it brief, is that... Well, I guess it depends on if were talking about a /limited/ amount of parallel universes, or an /infinite/ number of them. As in, for each possible outcome.

    In such a case, there would be Many of you. Just much less you then not you.
    More infinite not you then infinite you. IT TOTALLY MAKES SENSE, SHUTUP. I DIDN'T DECEND INTO BABBLING NONSENSE.

    On an interesting point, in the last 15 minutes destiny has come up 3-4 times for me.
    Strange, eh?

  29. :/ Blogger ate my comment, bad blogger, bad!

    I'll shorten what I said then:

    There is nothing wrong with
    "Ellen who is not Elliot, but has the same parents as Elliot" here.

    The multiverse pretty much guarantees every possibility does exist, but not every possibility is stable. The odds of actually finding a "nearly the same" universe is actually better than finding one that is completely broken to our way of thinking. To explain this, open up any program that lets you "zoom in" on a fractal, and follow one line for as long for several minutes (or just youtube one.) Consider the travelling down the line as the flow of time, the farther you go, the more possibilities branch out, but the farther away they get from your current position. So if you were to travel to a parallel universe all of these are "close by" as they branch off "you" as the common denominator. In the case of that Ellen, the common denominator is Tedd, not Elliot.

    In the universe with Kaoli and Ellen, that universe is is based off Kaoli's perspective, not Ellen. Ellen just gets "tuned in" to it. This also throws a few other interesting cards into the deal, dreams are also parallel universes that can be "tuned into" as well as time travel. That universe neither Elliot nor Nioi can exist, since the implication is that Nioi replaces Elliot in her universe. (Maybe the Lord Tedd-Shade Tail-Nioi universe doesn't have an Elliot at all.) Maybe because Elliot didn't exist he became Lord Tedd. Maybe the original Grace didn't die in that universe. The implication here being that Neither Shade Tail nor Grace are an "alternate" to EGS's main universe Grace.

    Maybe what we've known all along is that Elliot or Ellen are necessary for Tedd not to be Lord Tedd.

    My original comment had BTTF stuff in it but I think blogger doesn't like novel lenght comments.

  30. Infinite multiverse theory aside, as that's been done to death, I'll address why people always seem to find a universe so similar to their own and never seem to find one that's radically different. After all, even if there are infinite number of universes, there are more where things are redically different or absurd than there are where things are reasonably consistent up to a certain point.

    The idea here is that a new universe splits off for every possible quantum state an atom or molecule can occupy when it is measured. It is important to note that the measurement is required, thus limiting the number of possible universes to a smaller infinity. At that point, it is reasonable to assume that universes can be said to exist in a space of sorts and that each universe can be represented graphically and furthermore, since it is rediculously unlikey that they will somehow follow the exact same path from then on for every single quantum state measurement ever, it can be said that two universes will, in general, move apart from each other. So the 'distance' between them tends to increase over time.

    Now that's an interesting concept, this 'distance'. It could be represented as physical higher-dimensional distance, but it also represents how different one universe is from another. Either way, the most important way to represent it is that universes farther away require more energy to get to. Even if it requires less energy than walking to cross universes, it is reasonable, given the current understanding of physics and assuming it holds in higher dimensions, to say that the farther away a universe is, the more energy it takes to get there. I think it is likely that it will take a ludicrously huge amount of energy to accomplish this and so you are most likely to generate the minimum amount of energy needed to get to the closest universe, which would not be substantially different than your own and the difference would have happened right before you left. In fact, the difference could be so miniscule, you wouldn't even notice it was different. Aside from these universes, you are more likely to be able to get to a universe that split off not long ago as opposed to one that split off a billion years ago.

    Now, parallel universes. Earlier I said that it was highly unlikely that a universe would follow their parent universe's path at every point, however in a realm of infinite universes, such of them must exist. These special universes would be termed parallel universes because their lines ran alongside your own. They still aren't exempt from the idea that universes tend to move away from each other (an interesting form of entropy if universes weren't infinite in number), but for the moment they have been running nicely alongside yours. These universes are easier to get to because they will be closer to your own and will probably match in several of the important technical variables which determine a universe-crossing, whatever they are. Therefore they will be easier to get to than many other universes. And the ones in which you do exist are likely to be the easiest to arrive in.

    So, in conclusion, because of the energy required, you are most likely to end up, if not will always end up, in a parallel universe or a universe with a very recent split-time (with how recent being proportional to the amount of energy you have). If you have a ludicrous amount of energy then you can get to farther away universes, and if you have an infinite amount then you can go anywhere.

    Of course, if you have spiral power you just force the universes to come to you and destroy themselves when they realize they aren't worthy of you, letting you pick and choose the exact universe you want to visit.

  31. There's a lot to read through, but one in particular caught my eye:

    Matthew M. Murray - My comic is purposefully horrible when it comes to anything resembling genuine science, the last paragraph says I like it anyway, and the caption for the Family Guy multiverse episode said it was good.

    Point being, I'm not putting down when its done in fiction. I'm arguing that it doesn't make logical sense from the standpoint of reality, and I'd say the same thing any given day of the week regarding my own work.

    I wouldn't really call that "big talk" unless I was genuinely putting down other works of fiction. I poke some fun at Star Trek in the comic, but I love the mirror universe episodes and regularly help promote the franchise (as though they need my help), so I don't feel too bad about that ^^;

  32. Assume a three-axis model of time. The first axis is the classic "past-future" axis. The second represents "branches" - Here is where the United States lost the revolutionary war, and so forth.

    The third axis, however, measures -divergence-. So, even though a "branch" where the United States lots the revolutionary war is very distant on the second axis, you will, statistically, have sub-branches that are improbably close to ours.

    Therefor, as long as you travel heavily along the second axis, and stay "close to home" on the third axis, you'll get exactly these sort of utterly implausible variations.

    Presumably the people who travel along the third axis tend to die to unfortunate situations like "Earth is actually a hard vacuum", and this explains why you usually only see travel along the second axis :)

  33. madrussian90's comment contained an interesting line (at least from my PoV): "Any one of those 200 values is slightly different, no life. Slightly more different- no stars, even no atoms. 
But yeah, if universe hopping happens, there's likely some sort of filter."

    I once read that slightly different values for the constants prevented life from appearing (basically, life is a miracle), but slightly *more* different constants would actually prevent the universe itself to keep existing for too long (because, even if it isn’t necessarily as obvious as with life, having a 13.10^9 years old universe such as ours is a miracle in and of itself - most universes probably end much sooner than that). A stronger gravity constant would provoke a Big Crunch, for instance.
    It may sound silly, but can you reach an universe that has stopped existing altogether?
    Let’s suppose each universe has an unique address (let's say, an address formatted like (1; 4) or (2; 4) - you could therefore arrange the universes on an orthonormal map), would an universe's death “free” this address (so that a new universe could appear in its place), or would that precise address become Lost Forever?
    The first hypothesis (address liberation) is pretty creepy because it basically means that everything (*everything*) eventually gets erased. Just takes a looot of time in some cases.
    The second hypothesis (address conservation) is different altogether - considering how unlikely it is for an universe to last in the 10^10 years, most addresses would probably be dead as we speak. If multiverse traveling were to be invented, it’d involve being able to reach a “valid” address (in other words, multiverse traveling could be summed up as traveling from one point to another on the multiverse map - you miss the destination, you can’t even “get back” because you basically end up outside of any universe and probably stop existing altogether). Thus meaning that safe multiverse traveling would involve “mapping” the multiverse, and probably reducing traveling distances (we don’t send astronauts on Pluto, but we are thinking of sending them on Mars).
    If you think about what’s been said before in this thread, “closeness” in the multiverse map probably induces “closeness” from a content PoV, inducing that most multiverse travelers actively try to reach universes similar to theirs. Running into an alternate in this condition is probably more justifiable.

  34. And I got ninja-ed by mantic-angel about addresses. *flails*

  35. Just a few points.

    1) madrussian90 got it wrong; his sets A and B have the exact same number of elements. This can be proven by creating a 1:1 mapping of elements of A to elements of B. They both stretch to infinity, so you can do this easily; you'll just use up elements of A faster than elements of B, but there is an infinite amount of them, so you won't run out, ever. This kind of infinity is called "countable" (see

    2) There are indeed two flavours of infinity: countable and uncountable, with the latter being demonstrably larger than the former. Real numbers are uncountable; natural numbers are countable. Between any two real numbers there is an uncountable amount of more real numbers. Yeah, that's a lot. See

    3) The point can be made that it may in fact be impossible, not merely unlikely, for an "alternate you" to exist in an alternate universe. However, I seem to recall that it's considered to be theoretically possible (albeit _extremeley_ unlikely) for matter to materialise spontaneously; also, you could argue that as long as there are roughly humanoid creatures around, it would be possible (though unlikely) for e.g. cosmic radiation to cause DNA to rearrange itself _just so_ near the time of conception so that an alternate "you" would be born. If a) such occurrences are possible and merely unlikely and b) every possibility necessarily exists in an alternate universe, then there is nothing logically wrong with alternate versions of yourself being present in different altenate universes.

    Just having a continuum of alternate universes is not enough in itself; for example, the cardinality of the set is still uncountably infinite. Therefore even an uncountably infinite amount of alternate universes can "skip" particular ones.

    4) It'd be interesting to know whether the number of possible outcomes of every process in our universe is countable (though still infinite) or uncountable. For example, has it been proven that space is a continuum? What about time? If matter can only occupy discrete positions and time consists of discrete moments, then the number of possible states for our universe is countable (because energy is discrete as well, iirc). This then would mean that, assuming a finite amount of matter, the number of all possible states up to a point in time (at least the ones consistent with physics) _could_ be finite.

    If that were the case, a finite number of alternate universes could cover all possibilities.

  36. Alternate versions of ourselves with changesrom the distant past are pretty unlikely (Very much so), but that still leaves a different option, New alternate dimensions can always come into existence, splitting off from our own - so what if the world was destroyed three minutes after your birth and everyone flew off into space? What if a certain war was lost, the economy went bad, anarchy reigned, ANYTHING could happen in just the ____ years between the moment you were born and the moment you became old enough to know what dimensional travel WAS, which would create a seemingly whole new world.

    That means there are various alternate dimensions that split off AFTER we were born, in which alternate versions of ourselves WOULD exist.

    I do agree with the fraternal thing - outside of ones that came after our birth, chances of us being born the same are slim... even a second different in conception can create something new. However, there are probably more than one dimension where your parents met (it wouldn't really be an alternate version of you, physically, but it might be that universe's version of you.)

    Oh, and then you can go into sci-fi/fantasy territory - two dimensions that are bound closely to each other, and mirror each other, so that - even amidst thousands of differences - little random things, like people, tend to be the same between them. I think that last one might be possible.

  37. The thing is, most commenters on the are taking one of two tactics: pointing out that A.) since the multiverse has every possible possibility, there are an infinite number of worlds that are out there and *do* have the same DNA in different circumstances, and/or B.) making up a system whereby the chance of running into a similar world is increased.

    The reason that neither of these really affect the subject of Dan's article is a simple one: the vast majority of shows/books/whatnot that feature traveling between universes have it done *randomly*. You can't point yourself at a specific universe among the infinity out there, and there's nothing naturally pointing you. Alternately, when they do point, they're pointing for something other than "similar people, different circumstances".

    If you want to write your own alternate-dimensions story, one where the loophole's closed, feel free to use whatever method you want. But the stuff that Dan's talking about doesn't.

  38. Consider this:

    In a system of infinite parallel universes, the chances of hitting any specific variation are tiny. The more thoroughly you describe the target universe, the more ridiculous it is that you could possibly have ended up there.

    In fact, I would go so far as to say that for any given universe, the odds of travelling there and not encountering something so wildly improbable as to defy all logic are themselves infinitesimal. There are just too many variables, and they all vary too widely. In other words, it is nearly certain that no matter where you go, you're going to find something when you get there that makes no logical sense. These odds decrease the more similar the target universe is to your own, but of course finding a target universe that resembles your own in most significant ways is also improbable—unless you're travelling along axes of proximity, in which case, all those improbable similarities start making sense again.

    Given that, why not duplicates? They're as likely as anything else.

  39. I’d like to consider what happens when you put these arguments up to actual scientific work in multiverse theory rather than what’s been done in science fiction. As I understand it, the best multiverse practitioners have been able to do is come up with two non-contradictory ideas which can be jiggered enough that the numbers agree with one poorly understood facet of cosmology. That is to say, we have a starting point. Until some theory correctly predicts something that hadn’t been observed yet, that theory is of dubious value. In any case, a conservative estimate would put the probability of life arising in Universes that could have different laws of nature at around 1 in 10^50. This means that if life is probable, and there are only about 1000 Universes with life, there must have initially been around 10^54 Universes or there is some special reason for the numbers we see like the charge on the electron. Rebecca-kalista makes a good point in that most of the non-life Universes would ‘die,’ but unfortunately, only about half of them would crunch back into a point and kill off space. The other half of the ‘dead’ Universes would continue to expand until it would be impossible to find two electrons closer together than many light-years apart. By most definitions, that Universe is effectively dead, but contains a larger volume our Universe. Larger than any life-containing Universe created at the same time ours was, in fact. In any case, my point is that if we want to match up science fiction with science fact, (a treacherous undertaking to be sure) we need some mechanism that prevents us from finding dead Universes. We would also need something that stops us from arriving in the space between galaxies, between stars, between planets, inside planets, in the middle of the ocean, or anyplace we couldn’t survive. If such a mechanism exists, the odds don’t matter unless 10^51 Universes is OK but not a googol plex. You would get where you want to go because if something wasn’t keeping you in the kind of parallel Universe you want to write about, the odds of you surviving the trip are negligible. In short, if you can live in a parallel Universe, it’s very difficult to make the case for what can’t be there. This logic works whether the number of alternate Universes is infinite or finite.

  40. Perhaps the assumption should be that your soul would exist in each of these parallel universes, and the actual dna doesn't matter.

    That opens up the possiblity of your alternate self being male, female, a plant, older, younger, immortal, having different parents etc.

    Of course the biggest flaw with this idea is that we can't prove scientifically that souls exist.

  41. First of all, blogger, stop eating my posts! No soup for you!

    Now to the main point. A lot of folks are out there poking holes in Dan's theory/opinion of alternate selves without keeping it in context, as mentioned again by Dan himself.

    I think what Dan was getting at was how the whole thing is handled in fiction is so tenuous as to threaten his suspension of disbelief. By and large the Deux Ex Machina behind such "Mirror Universes" is abysmally poor, proving his Star Trek and super smartness statement.

    I'm also a Metaversalist ( ) and have had extensive discussions such as this with my fellow Metaversalists and others, both of scientific and non-scientific bent, so I've heard a lot of this before today.

    I feel, since we are talking about fiction, the fairest way to prove the feasibility of an alternate "you" in another multiverse in fiction, is to compare it to fiction where it is handled with more presence of mind than, say the "Mirror, Mirror" episode of ST:TOS.

    The first and older of these is the "Chronicles of Amber" by Roger Zelazny ( ). In this fiction, by and large the only people able to universe-hop are either unique in the universe (there not being a direct copy of them) or those who have "walked The Pattern" there is a Pattern that exists in the one "true" universe, and all the rest of creation is called "Shadow" Universe hopping there is simply one of the Amberites walking down the road and picturing small changes, so it is a directed travel, and The Pattern assures it makes sense. Arguably there are a finite number of universes in this fiction but it appears to be limited only by the imagination of the traveler, so it may be a "countably infinite" number.

    Another place it is done well is in the roleplaying game GURPS' "Infinite Worlds" supplements ( ). In this world the players are by and large from a universe they call "Homeline" and travel between universes follows the "similar is easier" model set forth by other bloggers in this thread. Encountering alternate versions of people, including yourself, is possible but rare enough for a person to encounter alternate versions of yourself or people you know might only happen a handful of times in your lifetime, which statistically still is not too rare when you think of the scope of infinity.

    Both of these works of fiction are in the same category as Dan, since they are aware of how sucky most fiction handles this and are super smart.

    There actually are a couple-three card games that handle time travel well, the most recent of which is, ironically the "Back to the Future" card game ( ) but to quote Kelly Bundy, "The mind wobbles!"

  42. Dan - thanks for your reply. No offense meant, as I think your comic is one of the genuinely best-written out there. That post was me being snarky for comic effect, and I guess it kinda failed in that area. But it does kinda ring hollow when one whose overarcing plot involves something he himself then proceeds to tear down. But don't listen to me: I'm a fan, and we're notoriously unreliable and wishy-washy. lol

  43. It seems most are willing to accept the premise that the quantum-splitting theory of multiple universes allows for all possible universes (which isn't infinite, since there can be only a finite number of possible quantum states the universe could be in since the big bang). And there exists some where the Revolutionary War was lost by the colonists but we're all still here. But the problem is that the odds are so low that even if such a timeline exists, the odds of finding it randomly when traveling to other universes or timelines is still vanishingly small.

    One possible theory that addresses that is the notion of energy states. Suppose that we define the difference in energy states of two different universes at a particular moment in time as the amount of energy it would take to change one universe into the other somehow. Hard core physics people will object to this, but its a colloquialism for simplicity purposes. In that case, we could theorize that for *some* kinds of dimensional travel (say, the timer in Sliders) the tendency is to locate and travel to universes with similar energy states. Traveling to a timeline with a radically different energy state would be more "difficult" because it would be a transition across a much larger "energy barrier."

    But if that's the case then why don't dimensional travels tend to find other universes in which everything else is *exactly* the same, not just mostly the same? Well, two things. First, maybe not. What matters is not just you and everyone you know, but the whole universe. Maybe (because the multiverse only contains all possibilities *consistent with the laws of physics*) all of the universes in which the rebels lost the Revolutionary War but we're all still *exactly* here are universes in which the external forces necessary to "push" the world into that state caused a lot of changes elsewhere in the world that we can't see. Maybe in those universes we're all still here, but the random events necessary to accomplish that are such that all the bacteria on earth are different. Maybe its a lot easier to get close, but not perfect, when such a change happens.

    Second, maybe the method of time travel *forces* some minimum distance to be traveled. Suppose the Sliders timer "pushed" you some distance in "multiverse-space." In that case, the one thing you can be sure of is that you won't land on a universe identical to the one you left. It has to be one with some minimum amount of distance from the one you just left, so there has to be at least some changes. This might explain some aspects of the timer. It had a "lock" which ensured the sliders arrived close to their origin point in space. In literal terms that's meaningless due to the fact the universe has no absolute coordinates, but when you think about it in terms of arriving close to the same relative position relative to the energy state of the universe around you, it makes more sense, and suggests the timer is aware of how the universe can change around them and tries to prevent overly radical jumps both in space *and* in energy state.

    This theory leaves at least two different ways to travel to alternate timelines. One: jump there. If you jump there, the theory says that you'll find yourself in a universe with a similar current state even if there are changes in the past. The harder you jump, the more "different" a universe you could find yourself in though. Two: causally travel there. Meaning: go back in time to the moment of some critical change, and then "flow" with the universe from that moment on, possibly at high speed, but without trying to "jump" between timelines (like HG Wells' time machine). In that case, because you're now following cause and effect, you could find yourself in a radically different timeline and universe than the one you left. Many alternate timeline stories might be explained with a hybrid of these two kinds of travel.

  44. If you want to read a good set of Novels about parallel universes, I recommend Piers Anthony's Mode series. It brings in the concept of reality anchors being both a place and a person simultaneously. Its also a very good read.

  45. An alternative theory is the time-traveling squad, also known as time-cops. They keep fixing those little details so the timeline kinda remains constant.

  46. I have a theory that specifically relates to time travel creating these other universes. Sort of like the marvel comics other universes but slightly different. Ok so starting off the Bermuda triangle is the doorway to the time vortex. Now that that's covered say you went back in time and changed something. Now another reality has been created. The original still exists but is just another universe. The way back is to go back again and stop yourself from doing whatever you did. It doesn't have to be like that circumstance to create another universe because a new one is created every time anyone has any choice. So there are an infinite amount of parallel universes. This also rings me to the theory of a whole universe sitting on an atom. This could be where these parallel universes are. Think if every atom in our entire universe was another tiny universe then it could possibly cover every choice ever made. Also I don't think a parallel you is based off of having the same DNA I believe you have a connection to someone in this other realm that is very close to your DNA but can have alterations. Perhaps this person has a smaller nose or faster metabolism or different gender and so on. Anywho that is my rant

  47. You know Dan, you're absolutely right. I considered these things before and use them in my stories; then I tossed them aside and used doubles in other stories.
    Bassically, it depends in the story you want to tell, you can be realistic or not. Either way I love the Ellens and the Tesses of the Multiverse

  48. Most people seem to have addressed the infinite worlds = infinite worlds that are just like ours but with minor differences, so I'll focus on the other major argument.

    All the universes originally started out as one universe. Every time a "choice" occurred (a "choice" being any event that could have gone in a different way, be it by chance or decision), the universe splits into two. Eventually there are an infinite number of universes. Now if you were to interact with a random one, chances are there would be nothing in common. However, as you mentioned, if you focus in on a recently diverged universe, you get the desired alternates scenario. All "alternate me's" scenarios work as long as they diverged sometime during my life and were by and large identical up to that point.

    However, if you'll notice, there is normally no interaction between any universes, even recently diverged universes, besides the act of splitting. So here's the important question: how does one find and interact with a desired alternate reality? The answer is, you create it. As is inferred on the show Fringe (an excellently thought-out version of alternate realities), the major difference between the two universes is an act of interaction between the two, which serves as a diverging point, and from that point on, the two realities are intertwined and further interaction becomes easier. By interacting between the two realities, this would in itself cause the change that splits the two.

    To put it mechanically, a device that tries to view another reality would want to view one that was just created. The most recent event that could occur either way is the viewer itself working. So in one universe, the viewer doesn't work, and in the other, the viewer looks into the former. An alternate process (sorry for the pun) would be if the scientists perform an event that relies on quantum physics that can go either way, and link it to the viewer.


  49. @Andras
    Um Don't remember the month of publication but my argument for differing values of infinity was taken more or less straight from what I read a while back in Discovery magazine. And if each number in a set has an exact correspondant in another set, but the second set has numbers that do NOT have correspondants in the first, that pretty much by logic and by definition states that the second is a larger set, for all that both are infinite. When you can assign a definite ratio, you have a basis by which to compare them. Just a 1 divided by 0 and .5 divided by zero are both infinite results, that doesn't change the fact the 1 is greater than .5, and therefore the resultant infinity from 1/0 is twice the size at all measurable points as .5/0
    Just my $.02

  50. Your theory only works if there is a set number of universes and that they all started the divergence before you where born. I'm sure others have said this but if a divergent time line happens at every choice that is made then there are an infinite amount of universe and both an infinite amount of universes where you exist and don't. Like sliders only some worlds had different versions of them.

    Example. lets say your born so right now that's one universe with you. but it splits and your parents give you up for adoption in one world but not there are 2 parallel worlds you live in. then the one where your put up for adoption your adopted by a bunch of different people as more parallels are formed...etc. S

  51. Sure that's all true, unless there are an infinite amount of other universes, so there would be an equally infinite (in other words, infinite) chance of there being another you in one of those universes.

    If someone said this already or disproved it or something beforehand, I haven't read this long list of comments at all, so sorry if that's true.
    EGS rocks by the way.

  52. ...and then I find out someone said the same thing, right above my original comment. Go me.

  53. I thought the idea was that an alternate universe exists if there is the slightest deviation in the outcome of an event (on any scale), relative to our timeline. It would seem to me that this makes for an exponentially expanding set of alternate universes. Wouldn't that create a greater possibility of multiple alternate universes with the same decisions being made up to the point of me writing this comment?

    While said universes may exist, I imagine the chances of finding one is very small. I couldn't fathom the mathematical engine that would be needed for such a task, not to mention the technology to view it or go there and return to the correct universe.

    What if that set of universes only begins to fill out after we possess the technology? What if the greater cosmic fabric begins to tear itself apart as the set fills out, borrowing energy/matter to make each continuum? What if the universe begins to unravel/rewind as a single moment at the beginning of time consumes the entire expanse of space/time?

    Or we could simply die of boredom as we begin to understand the patterns of all the decisions that could be made because we were able to review the alternate continuums. Either way, it would be catastrophic.

    All of that happened because we made an engine that let us look at alternate universes.

    Maybe it would be better if we just left that technology alone.

    *head explodes*

  54. "Who says there are bajillions and bajillions of universes?" Ed demanded.

    Dan shifted his weight so his elbow didn't make the bar creak so. "Actually, I believe it was the dragons. They're the ones who believe in the universal tree."

    "Tree?" Val spoke up. He was the Norse mythology fan. "You mean like Ygdrasil?"

    "Yeah, I suppose." Dan offered him a beer, which was accepted. "They say the universes ain't random. They tend to bunch together, like snarled threads, or the limbs of a tree, and the branches grow into ever more closely related smaller branches. And you can't go into the universes on your same branch, so there's no chance of running into yourself."

    "I'm gonna need more beer," Ed stated.

    "Well, you can get your own. I bought last time."

  55. I didn't really read all the comments since there are a lot of them and they are long, but I'd like to point out two things.

    1. The odds of an alternate of yourself existing in a parallel reality may be astronomically small, but if there are an infinite number of parallel realities, the existence of such an alternate is pretty much guaranteed.

    2. If you're using Back to the Future as an example of how parallel realities might work, you must be getting a little confused. Back to the Future doesn't use parallel realities; it uses something more like ripples of paradox spreading up and down the timeline.

    Also, I'd slightly broaden the definition of alternate to merely require that both your parents have the same DNA and you have the same number of older siblings... or something. I dunno, but the point is it should allow a true opposite gender alternate.

  56. If you were to use identical DNA as a benchmark, it is interesting to consider that there is a possibility (extremely low, but...) of different parents concieveing the same child, particularly in environments where there is little in the way travel.

    Also, it depends on how universes are filed. It might just so happen that it happens to be easier to move to a universe that split off more recently and thus after you were born, or it may just be that similar universes just hang out in together.

    When it comes to defining my alternate, I would take memetics as well as genetics into account. Were I to stumble into a universe where the short, quirky pun-spouting, science worshiping gamer position is held by someone who deviates strongly gene-wise, it'd be another me just the same.

    One thing people need to remember (it's a trap I fall into myself) is that if something is infinite it doesn't necessarily contain everyhting. Maybe all alternate universes are pretty much identical, maybe when you leave this one you end up in a universe exactly the same as this, where your alternate just that second left to go explore the multiverse... and so you chalk it up as a failed experiment. Every single time.

  57. Yeah, I'm glad stuff I've done is based in a system where something other than DNA links dimensional counterparts.

    Especially since I'm less than enthusiastic about the every-possible-event-creates-more-worlds thing.

  58. Owen said:
    "One thing people need to remember (it's a trap I fall into myself) is that if something is infinite it doesn't necessarily contain everyhting. Maybe all alternate universes are pretty much identical, maybe when you leave this one you end up in a universe exactly the same as this, where your alternate just that second left to go explore the multiverse... and so you chalk it up as a failed experiment. Every single time."

    It's quite true that an infinite set doesn't necessarily contain everything, but when you consider the way an infinite set of parallel realities is (typically) constructed, it's easy to see that it is, in fact, a universal set (ie, it contains everything).

    In case it's not as typical as I'm led to believe, the way to construct this set of parallel realities is to start at the beginning with a single reality; then, whenever there is more than one possible outcome in one reality, replace that reality with as many realities as there are possible outcomes. (It's entirely possible that this set is not infinite; even if it isn't, though, it clearly contains all possibilities.)

    On an unrelated note, could we get the comments to accept the BLOCKQUOTE tag? It's very useful for quoting other people, and it's not at all dangerous (all it does is indent the text a bit).

  59. So there are several different theories regarding different universes. One that I find the most plausible is one where our universe is in fact a infinite multiverse in that it goes on forever with an infinite amount of galaxies solar systems and planets and thus if it is in fact infinite then there must be an infinite number of planets exactly like earth and if there is an infinite number of earths then every possible thing that could ever happen on earth well there is a variation of that in the infinite multiverse theory

  60. It was mentioned that various "clustering" theories only work if you ignore that travel is usually "random". Except... if you look at, say, Slider's, they're very explicitly AIMING for "home", so it makes sense that they'd find things that are clustered near to that. What's more, "Has an atmosphere, has humans" is some pretty impressive accuracy :)

    Most fiction has the travel uncontrolled, but not necessarily random. Just like if I close my eyes, spin for a while, then throw a stone. I probably can't control where it will land very well, but if I do this in the United States, then the stone is unlikely to end up in Australia. Just because it's uncontrolled and even "random", doesn't mean it's exploring the ENTIRE set of alternate universes.

    I do also like the Fringe-based theory that travel has to be amongst divergences created BY that travel :)

  61. I find it ironic you think this when your comic clear does have alternate universe versions of people.

  62. Parallel universes are impossible because they would destroy themselves. If there was even the slightest possibility that they would, e.g. come back in time and and destroy the world, they would. Therefore either parallel universes and time-travel don't exist, or time-travel doesn't exist.

  63. Are we taking into account that there might be infinitely many universes?

    I have a...hypothesis, that involves something of a "Map of the multiverse." Assuming that the multiverse is potentially endless, that would mean that, despite the odds, it's practically guaranteed that there are alternate versions of a given individual.

    @ Edward: Just because we haven't developed the means to travel through time doesn't mean another universe has. So don't discount parallel universes as an impossibility. Not only have parallel universes have reportedly been proven mathematically to exist by Einstein, but some credible scientists, including but not limited to Stephen Hawking and Michiu Kaku are lending their credence to a theory that the Big Bang was started when two universes collided with each other, and began to merge together.

    1. Your statement about Einstein is sadly false. I wish that rumor were true. Hawking and Kaku have both speculated about this possibility, but their musings are actually "conjecture" at this point, and not theories. In order to become "theory" a claim must be testable, and falsifiable. Current science does not give use the means to determine whether there is anything outside of the "Universe". It is currently equally likely that 1. There is only one universe 2. There are a finite number of universes 3. There are an infinite number of universes 4. The first three don't make sense because our current perspective of what a universe is... is actually incorrect. All four of these are "equally likely" simply because there is no scientific evidence in support or against any of these claims. That's why science is so fascinating though; maybe one day soon, we will be able to test some of these big questions.

  64. Or just accept that for each N universes, using the pigionhole principal there has to be At Least two in which the dimensinal X factors coincide. Using the Star Trek example as a set, it is possible that the cause of the dimensinal transferrance acted as a naturally occuring set equalizer, causing the direct coincidence between The varying dimensions and bypassing all the other, infinite numbers of universes where the dimensinal factors Did Not coincide; creating the illusion that all paralell universes contain the same people between them.

    - Yay Quantum-

  65. Oh man there is no way for me to read all these comments.

    But like so many others I am going to rant away about this anyway.

    Basically what I want to point out is that quantum theory does sort of involve a certain *distance* between the different universes, and we are closer to ones which are less divergent so it makes sense that we would have easier access to them, if there really is any way to interact with other quantum possibilities. (Roughly speaking such interaction definitely happens. Having it happen on a large scale, between fairly distant universes, is the difficulty.)

    Besides that, there is just not much science telling us how chaotic our lives are, and it makes perfect sense to leave it up to individual author to decide how much the butterfly effect really changes peoples' lives. A lot of stuff seems random but is really inevitable, like maybe a random encounter in the elevator leads to getting a certain job, but really you would have heard about that job from one person or another anyway. Some differences get magnified over time, but others, like what you had for breakfast a year ago, may simply fade into making no difference whatsoever.

  66. I disagree. A dimensional alternate does not have to have "identical DNA" and identical circumstances surrounding their birth in order to exist. Different parents, different time of birth, and different factors in their lives could potentially lead to a person LIKE the original, but not identical in DNA or demeanor, or even appearance and or gender.

    A dimensional alternate doesn't HAVE to be totally intertwined with what happens to their alternate universe counterpart, and vice versa, although with all the infinite universes out there, it's impossible to say that there ISN'T a way for alternate timelines of the same reality to exist, either.

    Ultimately it's all based on interpretation, as it's a science that we can't explore in practical ways... Yet.

  67. i will only say one thing:
    given that there is a set of all universes, the odds of whether a universe exists where any arbitrary set of conditions applies to it is irrelevant if it is greater than 0.
    TD;DR: There exists a universe where i have the force, am the king of France, and Nanase is my wife. (it is only because of this fact i can sleep at night :P )

  68. This depends upon whether there are other universes at all, and how many other universes there are. Probability and infinity work together in very strange ways. If there are an infinite number of universes, not only would a parallel universe similar in every way certainly exist, but an infinite number of these would exist. In fact, if there were an infinite number of universes, then every possible universe would exists, and there would be an infinite number of each of these universes. However, if our universe is the only one, or there is a finite number of universes, it is impossible to highly unlikely that any universe even remotely like ours would exist.

  69. Now, as so many people have said before me, this is only valid in a multi-verse of finite universes. HOWEVER! A finite number of universes is required for anything to exist. Because if, as so many have said, an infinite number of universes means that every possibility exists somewhere, then somewhere there is a madman who has destroyed all possible universes. This has, obviously, not happened. Therefore, the number of universes must be finite. Therefore, your point is completely valid ina Ny existing multiverse.

    1. Even if there aren't infinite universes, there could still be so many that it would be almost a mathematical certainty of finding alternate versions of ourselves in some of them. So his argument is still invalid.

      Also, I'm pretty sure you're incorrect in your logic about why there can't be infinite universe. Otherwise I'm pretty sure all those physicists would have figured it out and the many-worlds interpretation would have been put to rest in short order.

      I'm not a physicist so my logic could be totally wrong here, but I don't think an infinite number of universes mean every possible permutation has to have happened. It just means an infinite number of permutations have to have happened. Which I don't think are the same thing. After all, you can have an infinite set of only prime numbers — but that set does not contain *all* numbers. In the same way, a set of infinite universes might only contain universes where a madman did not destroy the multiverse.

  70. So, for it to be reasonable (at least in fiction) for a random universe jump to find my double in an infinite number of universes: there is a god and that is ME! BWAHAHAHAHAHAHAHAHAHAHAHAHAH!

  71. Looks like at least a dozen people have covered what's wrong with your logic already, so I'm just going to facepalm.


  72. Identical DNA? I just need to say 2 words: Lord Ted. :-p