The Universe Rant · 6:21pm Mar 9th, 2017
RB's Infamous Universe Rant
You keep using that word. I do not think it means what you think it means.
This is a projection of a spinning tesseract. Tesseracts have four dimensions. They do not not have four universes.
There's a certain pet peeve of mine that I'm somewhat infamous for, in certain circles. Today, I'm going to explain why it bothers me, and hopefully teach you all a thing or two in the process.
"It's okay," Sci-Twi said as she adjusted the device she had cobbled together from an old calculator and some pocket lint. "We can use this to hop into another dimension, one where we've already solved the problem. Easy-peasy."
"Gotta love the multiverse," Sunset replied, taking Twilight's hand. "Onwards and upwards?"
"Onwards and upwards."
And with a flash, they disappeared.
Can you tell me what was wrong with that passage? No? Then keep reading, because this is a rant for you.
Yes, you specifically. Because you are the problem, and you don't even know it yet.
Let's begin.
Alright, so imagine you and I are having a conversation. It's IRL, too, so you know it's hypothetical.
I say I'm going to eat an apple.
I then proceed to take out a pear.
I then eat the pear.
"That was a delicious apple," I say.
You ask why I've trapped you in this horrible hypothetical purgatory. I tell you I'm proving a point. I then proceed to kill both of us by ending the analogy.
How does it feel when I call a pear an apple? Are you confused? Maybe slightly annoyed? Good. Now, imagine if I were an apple farmer, standing in the middle of my apple orchard, writing a book about apples as I simultaneously compile my university lecture series on the various species of apple. And it's not a joke, and I'm not doing it for any reason; I've just casually insinuated that I, the resident PhD in Appleology, cannot tell the difference between an apple and a pear.¹
You'd call me mad, right? Maybe think I was having a stroke? At the very least, you'd accuse me of being a moron.
Good. That's the correct response.
So stop calling apples pears.
Because if you can't point out the mistake in the paragraph at the top of the page, then you've probably been doing that your entire life.
Here's the mistake:
We can use this to hop into another dimension, one where we've already solved the problem.
That word right there. Dimension.
What Sci-Twi's describing, right there? That's not a dimension.
That's a universe.
There's a goddamn difference.
Dimensions, in physics, are at a very basic level equatable to directions. For instance, we are three-dimensional beings. We can move forwards/backwards, left/right, or up/down. These correspond to the x, y, and z spatial axes.²
In mathematics, dimensions are a property of an object. This property is determined by the number of dimensions required to describe the object: a point requires zero dimensions, a line requires a length, a plane requires a length and a width, a cube requires length and a width and height, etc. This property can also be measured by the dimensions of the shapes that bound the object. A tesseract is bounded by cubes, which are bounded by squares, which are bounded by lines, which are bounded by points.
Note that, in both of these definitions, we have not made any mention of the multiverse, the many-worlds interpretation, Schrödinger's cat, or any other similar concepts.
Now, a universe is the sum collection of everything. All of time, all of space. Everything. We live in our universe.
The multiverse is the collection of all possible universes. All of every time, all of every space. Everything that can happen, has happened, could happen, will happen. All of it.
Note that, in both of the above described concepts, the word dimension has not been used once.
Because they aren't the same thing.
A universe and a dimension aren't the same thing.
You cannot travel to an alternate dimension, because there is no such thing as an alternate dimension.
The reason for the confusion, I suspect, is lazy sci-fi and comic book writers who couldn't be bothered to do their research. Although this dates back to a time before the internet, back when research meant going to a library and sitting down with a textbook rather than a quick Google search, so I can't really blame them too much. People who make the same mistake nowadays, however, have no excuse.
"Now RB," you may be furiously typing, "it may not be technically accurate to call a universe a dimension, but it's in the common vernacular! Language evolves. Get with the times, you old fart!"
Well, for one thing, technical terms don't evolve in the same way language does. But yes, okay, I get it. Most of us are never going to be speaking in a setting where this would actually be important. It's in the public vernacular. I'll fight it as hard as I can, but it's going to be a losing battle, and I'll look like an ass for it.
But let's go back to that paragraph from before.
"It's okay," Sci-Twi said as she adjusted the device she had cobbled together from an old calculator and some pocket lint. "We can use this to hop into another dimension, one where we've already solved the problem. Easy-peasy."
See, this is where it gets relevant to writing. Because Sci-Twi? She's a smart gal. And clearly she knows a fair bit about theoretical physics, seeing as she was able to cobble together a universe-hopper.
So she would know better. In fact, anyone smart enough to construct a device that does anything with universes would know better, much like any apple farmer would be able to tell the difference between an apple and a pear. Which means it's out of character.
And we all know how much people on this site hate it when characters act out of character.
But even in original fiction, this is immersion shattering if you actually know anything about the subject. Which, if I've done my job right, means I've just ruined about a quarter of all sci-fi for you forever.
You're welcome.
1. Excepting Pyrus pyrifolia (the Asian pear), which closely resembles an apple.
2. As an aside, the fourth spatial dimension is not time. Time is the temporal dimension. The concept of time as the fourth dimension is somewhat outdated in modern physics, especially when considering models that predict more than three spatial dimensions. The fourth spatial axis is labeled as w, and represents the directions ana and kata.
I've always been fascinated with the theory of the Multiverse. But I have a question that pertains to this subject; Quantum Immortality.
I'm assuming you're familiar with it. If not, I'd recommend looking it up, because it's reeeally interesting.
What if, in one universe, I have a loaded gun pointed to my head. Every time I pull the trigger there's a chance I'll shoot myself. I've pulled the trigger 3,000 times, with no firing.
But, this doesn't make sense. According to the natural degradation of resources, I have to die. If not from the bullet then from natural causes (probably from sitting on my ass so long I develop some serious problems). Unless my body is made up from nothing but particles that don't have their polar opposite. So, in a sense, it's Quantum Mortality(with a hint of danger ).
Other than that, I agree. Except instead of the analogy between an apple and a pair; I'd say something along the lines of comparing a tennis ball to a rocket ship. The difference is unparalleled. They're not even remotely similar besides having a couple elements in common.
Also, what story is that? It reminds me of the show Sliders (oh my god I LOVED it ,too) so I'd also love to read it.
4459795 You are correct about the overall mortality, assuming there are no universes where you inexplicably become ageless through some unknown means. However, the thing to keep in mind is that quantum immortality is a thought experiment, and your overall mortality falls outside its scope. The idea is that it's Schrödinger's cat from the cat's perspective, wherein we only care if they are killed by the poison or not. Yes, it will die eventually, but in the isolated case of the box, considering only the poison, the cat that survives each time is quantum immortal. Likewise, with the gun to your head, the thought experiment only considers death by gunshot.
I suppose I had fruit on the brain when I wrote this; I was probably hungry.
Unfortunately, the paragraph was made up as an example; it is not (currently) a story.
However...
You might want to keep an eye on this guy. He's got a novel in the works you might enjoy, once it comes out.
4459992
Oh, okay.
Thank-you.
Good point, never thought about it like that.
Then again, the Quantum world makes little sense.
Directions weren't clear enough, I turned a potato into a hamster (originally I wrote it backwards, but that's horrifying). But anyways, that's interesting. I wonder if there's a universe dedicated to nothing but Schrodinger's Cats in both states.
Hell, that's even more disturbing. I love kitties.
ForgetthatIsaidthat.
Rainbow Dash loved danger. Really, she just loved excitement, but nothing could be more exciting than being in danger and successfully escaping it. Therefore, when given a chance to get in danger, Rainbow would take it, get in danger, get herself out of danger again, and hoard the surplus excitement as jealously as a dragon. She had gotten rich off of this investment scheme and would do anything to continue it.
Even pay attention to the blackboard, at least for a few minutes.
"So obviously we're barred from this other dimension by normal means," said Twilight, going into waaay too much detail about this supposedly dangerous (i.e. cool, exciting, not at all related to lengthy physics lectures) mission. "The only way for a pony to get to a different dimension is to use a thaumic active orthotic field disruptor to --"
"Wait," Dash interrupted. "Don't you mean a different universe?"
Twilight glared a moment at the interruption. "No, Dash, this is a different dimension. Anyway, to get there we have to perturb our orthotic fields by --"
"But you said it's a whole world that's like ours except everything's different! That sure sounds like a different universe. I thought a different dimension was like when it's really easy to prank ground ponies because they never look up, or that mare you showed me on Youtube folding weird shapes out of paper."
Twilight's glare was shifting to more of a beam. Dash's interruption was deeply misled, sure, but she seemed to be engaging with the underlying ideas surprisingly seriously. And now that meant Twilight got to explain more! "No, Dash, this is a different dimension. I mean, technically, it's a different neighborhood of locally Euclidean dimensions within the hyperdimensional hypermanifold that our universe consists of, but that's kind of a mouthful and just calling it a 'neighborhood' is even more misleading, so I'm using 'dimension' as shorthoof."
"But... it... that's not what a dimension is! You're talking about going to another version of Ponyville where everypony's evil and day is night and the weatherpony is a lame dork with a grey mane! Everypony knows that's what's called an 'alternate universe', it's in every comic book!"
Twilight went back to a glare. She had forgotten what a large gradient Dash's incomprehension could put on her beam-glare spectrum. "Comics are not exactly precise with their use of physics terms, Dash. An alternate universe would be a completely disjunct set of, of everything! It would be definitionally impossible to get there from here!"
"You said when you went back to high school that that was an alternate universe."
"That was magic! The mirror is magic so it doesn't count."
Dash stubbornly failing to be enlightened. "How is it different? I thought we were using magic to go beat up the evil ponies in the crappy evil universe!"
Twilight's glare darkened ominously to a glower. Dash's storm of misconceptions was starting to fly as fast as her. "It isn't -- okay, first of all, they're not 'evil', they have an inverted morality matrix because the whole region is reflected across the axis of..."
Twilight closed her eyes and massaged her snout with a hoof. She couldn't win with this approach. If Dash was going to understand, it had to be in laymare's terms. "Okay, imagine, like, you need to go to Canterlot. You fly west-by-northwest for a certain distance, right?"
"In about thirty seconds!" Dash stood and opened her wings proudly. "Why, you need me to go there? Maybe get some weapons from the royal armory for the dangerous journey?"
"Absolutely not! We aren't even trying to fight, it's just a scouting mission,and anyway you wouldn't be authorized, to do so on my behalf I'd need to fill out..." Twilight took a deep breath. Focus. Explain the machine, then the mission, then leave. "Imagine you had magic wings, that could take you in a direction you can't even comprehend. Things are different, just like moving to Canterlot, but since you haven't gone north or south or east or whatever, so it's also still Ponyville. It's just... changed."
"Oh, okay. So what's an alternate universe?"
Twilight felt her beam hesitantly returning as her explanations finally sunk in. "An alternate universe would be if, say, there was another Ponyville, but it's not next to ours or eckwards of ours or anawards of ours or on another planet. It's not even 'somewhere else', because there's no 'where' connecting it to us, not even the weird kind we're going to use to get to another dimension. But with enough magic, I could get there, but not by 'traveling' there even in a magical way. I'd just stop being part of this universe and start being part of that one."
"Ooookay, I think I get it now." Rainbow tapped her chin with a hoof thoughtfully. "Which was it when we were all superheroes in Spike's comic book?"
"Well, it could have been a pocket dimension... but it had its own fundamental axioms that weren't from our world, like a different universe... I'd probably have to study the -- why does it matter!?!"
"If it doesn't matter, why do you care so much?"
"I -- I'm not -- can we get back to the mission already?"
"If you stop yammering about physics!"
"FINE. GET IN THE MACHINE."
Evil Twilight cackled evilishly, a habit of hers Twilight was rapidly growing bored of. "Foolish mare!" she cried. "Will you not fight? You weak ponies deserve our domination so fully that I am shocked you can exist without it!"
Another wave of evil magic coursed through Twilight's battered body, a sensation not unlike being shocked or exercising with Rainbow. "Twilight!" called Rainbow from the cage she was trapped in, swinging from the ceiling. "You have to fight!"
"No!" Twilight screamed through the agony. "Dash, they're doing the right thing by their standards, and I could never hurt a pony for that!"
"She literally introduced herself to us as 'Evil Twilight Sparkle, Evil Queen of Ponyville and All Equestria'," replied Dash. "I was captured by Evil Rainbow Dash and Evil Fluttershy." The latter of the two had been faster. Dash still wasn't sure whether to be embarrassed about that on her evil-own behalf.
"I, OOOWWWWW, can still, OH CELESTIA WHY, find a diplomatic solution!"
Evil Twilight cackled again. "Even at the hour of your defeat, you bicker! How delicious it is." Her cackle somehow grew yet more ominous as she finally ceased the attack and approached Twilight. "I cannot wait to watch all of you despair like this when we invade your universe!"
Twilight finally shut her up with a blast from her horn. "We will never fall to the likes of you, monster!"
Okay I was just trying to cheekily point out how this whole confusion derives from how "Flatland"-style adjacent dimensions allow the same kinds of alternate-whichever stories as the many-worlds interpretation of quantum mechanics even though they're very different concepts, so you shouldn't worry too much as long as you're consistent with your terminology, but things got out of hand a little WHOOPS
5089761
Pardon me if this comes across as rude, but if you're saying that I'm incorrect then I would much prefer you just say that and point me at relevant sources as to why that is. Even after reading your (quite funny) diatribe twice over, I'm really not sure what you're trying to explain.
5089774
I'm sorry! I think I let that get away from me with the assumption that my sheer wall-of-text-ness would indicate that I found the premise of this post worth considering. I stumbled here all the way from Estee's blog post about you reading One Extraordinary Time and read this post and found it amusing, and then it got my brain firing about a counterexample scenario, and then that became its own thing. I'm a little worried that in the process it came across as sniping or something, which is not at all how I meant it.
That said, I think you're also getting that impression because, uh, I think I do disagree with you. I mean, I generally agree with your points; "other dimensions" are not the same as "other universes" in any way, shape, or form, consistency is important, and the many-worlds interpretation of quantum mechanics is definitely about alternate universes and has nothing to do with dimensions. Maybe most importantly, "alternate universe" is what people usually would mean to say if they knew what they were talking about.
But I do have an objection, or at least a footnote, that I should be more straightforward about, and it does go back to Flatland. Flatland is set in a two-dimensional world that is embedded within a three-dimensional world. If a flatlander could travel through the third dimension in space, they could visit alternate worlds that are functionally other universes, but exist within an alternate dimension of space; the same concept can generalize to higher dimensions (I'm not saying it does, in our universe; I don't know enough about theories of physics involving higher dimensions to say, and it sounds like maybe you do). C.S. Lewis's The Dark Tower uses a similar premise, where time has a second orthogonal direction allowing one to travel "andwards" and "eckwards" as well as forward and back; this allows visiting divergent timelines. I agree that this explanation doesn't really make sense with modern physics (to my understanding), and (more importantly for fantastic storytelling) I also agree that referring to such an alternate world as "another dimension" is grammatically suspect at best. However, there is a tradition here of using the concept of higher-dimensional geometry to explain the existence of other worlds, rather than using anything involving quantum mechanics. In a story using such a premise, "alternate universe" would be wrong and "alternate dimension" would be better (though "another plane of existence" or "alternate timeline" would be better still).
The other part of the objection is that I'm not sure it matters too much for most stories. Usually writers want to portray another world so they can show an evil Twilight who has a weirdly goatee-like tuft to her coat and rules Ponyville with an iron hoof, and the terminology is just technobabble to justify this. I recently watched Into the Spider-verse, which uses the many-worlds explanation, and I don't think the plot would have to change one iota if it used the alternate timeline explanation instead. I mean, I agree that it would probably be the worse choice in this case, but it would serve the function of the plot and there are understandable reasons (if not rooted in modern physics) why it exists as a trope. Since most stories of this kind aren't really about the mechanism at all, I don't think I can state a definite preference for one in general. (You seem to think that many-worlds is always preferable because it's more scientifically valid, but personally I don't feel the need to worry about that in outright fantasy stories -- not because I think fantasy writers should just throw anything in, but because there's no wave function collapse that allows magic to exist.)
Still, you're totally right that calling it "another dimension" is a profound misstatement of what a dimension is. I've never even really considered that and it's actually pretty grating. And certainly we agree that the terminology should be consistent. I just wanted to play around with the idea by looking for counterexamples, and in particular I think it's amusing that FiM has the right kind of kitchen-sink worldbuilding for the two concepts to both actually, independently exist.
Sorry to hit you with a second somewhat contrarian wall of text in one day. Usually when I get to the point of blabbing about stuff this much it's an active conversation and not an old post no one's expecting activity on.
Out of curiosity, what would you recommend for "pocket dimension"? That's usually a pretty distinct concept from alternate universes and such, and rooted in space-folding weirdness, but as you say it's certainly not a "dimension" the way the three axes of a space are.
5089921
Oh, no worries! I was just a little confused.
The first point you bring up is quite interesting, actually. I'd never considered it before (I'll read Flatland eventually, I swear). As you say, I don't think that's how it would work in our reality (I've had no luck finding any published literature on the idea, either), and I suspect any variations between such planes would be a lot less clearly delineated than anything predicted by the many-worlds interpretation, but the concept certainly makes for interesting science fiction fodder. Thanks for expanding my frame of reference!
As for point two: yes, you're absolutely correct. The actual mechanism is totally unimportant for 99.9% of stories, and this is 100% just a big nitpick. But it's a prevalent enough misconception that I felt it was worth it to address.
That and it irks me.
As for pocket dimensions, pocket universes might be an actual thing, and mathematically speaking there's a geometry called the Bag of Gold proposed by Wheeler that could maybe fill this kind of role. As we're talking about a separate portion of universe-like space, I think calling it some variation of a universe would be perfectly applicable. You could also just use a higher-dimensional hypershape like a tesseract for this sort of thing, as its internal area would be defined in more dimensions and thus have a predictably greater volume internally than it would appear to externally in three dimensions, but then you're limited by actual space constraints.
5090033
I have pocket universes on the mind because I read "Blink" and some related fics recently, and this line is used to horrifying effect as the premise of "Rapid Blink".
It's very short, and it's in the public domain and therefore easy to find. On the other hand, it's actually mostly a not-that-incisive parody of Victorian gender roles. But there are lots of cool details, like how being constrained to the 2D universe means everything is seen head-on (so e.g. a line segment looking at you is invisible).