Ventifacts and Yardangs

@Chronocidal Already considered it. This is actually completely doable, and in general, portals can move through other portals with no paradox. It completely derails most naming schemes, though, and since it's a very rare occurrence in my story, I figured I'd avoid the chaos and just not mention it. :)

@AdrianoRepetti cyber101 had an answer below which suggested the same thing (though without the file analogy, which I quite like). My only concern with it is that name changes will still be required after each portal opens, from the perspective of the "copy" universe. Read through the comments on that answer to see what I mean, hopefully my back-and-forth with cyber got the point across

@Chronocidal I'm not sure what you mean by "punch a portal". If you mean it like "punch a hole in something," as I've said many times now, there are no loops. Any time you create a portal, it generates a copy universe. It never leads back to a universe already in existence.

@JustinThymetheSecond I have literally no idea what you're talking about. There's no causality issue here. It's just that from the moment in time when the portal opens, the two parallel universes start the same but are allowed to take different paths. There's no spawning or anything, it's just 2 copies of the same universe. You're not accessing new universes, you're cloning existing ones.

All worlds are perfectly duplicated at the moment a portal opens. That means that both are identical at that moment, including everything that happened before. They have identical histories, yes. Then they can have different futures from that point on.

@TitaniumTurtle I know the feeling. :) @ JustinThymetheSecond Hopefully there's a numeric system so people don't get emotionally invested. Nobody I know of cares what their country's 3-digit phone code is.

@JustinThymetheSecond No, it's not possible for any portals to link universes already in existence. Each new portal activation strictly doubles the current number of universes.

@user535733 "Whelp, sorry everyone. Looks like some idiot set up a new portal, and now this entire universe, the Earth and all the uncountable stars and infinite complexity, is now collectively called 'The Fighting Mongooses.' Look, I didn't make the rules."

@JohnO Definitely a good answer. This will probably go in a book one day, and even if it's a little unrealistic, I don't want to start any sentence with, "Back in Universe 36A_ver7;Toyota_claim803"

@Morfildur Yes, yes, black hole and all that. Everyone wants to be clever. Trust me, I put thought into this duplicator, and I asked the question the way I did because I was sure that flooding the Earth with infinite mass wasn't going to work. Won't stop half the people here suggesting it, though.

@Chronocidal No, specifically the cars moving through the duplicator have been driving in circles for hours, coming out of one side of the gateway and into the other, over and over, through several parallel universes, until they arrive at yours. In the case you're describing, they'd fall out of the portal and have to climb back up over and over again. Needless extra effort, no breaking energy conservation.

@Separatrix Not intrinsically. The limiting factor is really that using the duplicator isn't legal, and you probably won't be able to create more than a few tens of thousands of duplicates before the government catches on.

@Michael I don't want to get into how the duplicator works because it's complicated and prone to misinterpretation. But yes, it's only a gateway, so anything that comes out of it has to be able to move on its own power. That's why I assumed you'd want to use a car.

@Telastyn You know what's scary? The US alone is already producing so much CO2 that this wouldn't make a dent. It's comparable to hundreds of cars driving into volcanoes every second. I wasn't expecting this question to lead to my daily dose of climate dread, but here we are.

@AlexP All of the clones are created with his memories, including his plan which he came up with before he used the duplicator. So they all start perfectly on the same page. And all of them are well-trained and capable of leading, tactics, taking orders and dying, so I don't see why he'd have trouble filling all of those roles and creating a chain of command.

I had the US in mind, but if another country might be easier to infiltrate, then by all means. I'd just like to know the option that leads to maximum destruction.

If this type of movement is valid (and I'm not sure that it is), it doesn't require bilateral symmetry, and might be a reason why it wouldn't have evolved in the first place.

For instance, if you picture the worm turning itself inside out, moving its insides forward and pushing backward with its outside skin, that's a mode of movement that's available in 4D (in this case the 'insides' aren't the actual 4D interior of the worm, but rather just a 3D cross-section). Like in the animation from the Wikipedia page on hypercubes: en.wikipedia.org/wiki/Hypercube#Related_families_of_polytopes

In 3D, a sea-worm-like creature can wiggle in the plane perpendicular to its body to move forward, but it prefers to pick an axis in that plane, since that involves less movement. In 4D, I'm tempted to say that it still picks an axis, but it's not as clear. Infinite lines can move around each other in 4D without changing direction, unlike in 3D, so that might allow the worm movement options that involve what from our perspective looks like it's moving its body through itself.

Hm, I'd need to think about both of those points. I'd argue, that yes, bilateral symmetry has an advantage even if you're limbless and crawling or swimming, since then you move straight when you wiggle side to side. The real question is, does that also happen in 4D?

I think we should ignore the lightning part of the argument - my understanding was that it was just to show that individual atoms vanishing do not produce sound (which, yeah, I kinda figured the wind would be more important, setting aside the point that it doesn't really make sense to talk about sound at the scale of air molecules anyway).

@JBH Could you explain your third footnote in more detail? What makes you think that it would punch a hole in their hand? When they ended the effect, a dime-sized area (2.5 cm^2) times 2 cm means 5 cm^3 of air would rush toward their hand at, let's say, 500 m/s, the mean speed of air. That's a momentum of just 3 g m/s. For reference, a paintball is about 3 g, it moves way faster than a meter per second, and it won't put a hole in someone's hand. I feel like it's easy to get carried away looking at just the wind speeds without thinking through how much air is really moving.

As for the cost, yeah, sorry, I drifted away a bit from your specific economics there. What I had in mind was a case where building the portals was the expensive part, but turning them on and off rapidly just cost a few cents of electricity. As opposed to your case, where it seems like each individual portal activation costs a lot of money, and thus turning a portal on and off is a huge expense.

I figured that the portal boundary was 2d despite the fact that it could only exist within a 3d intersection of spaces. The reason being that at any time, an atom has to be within one universe or the other, so the line between the two has to be 2d. Otherwise, you'd have some sort of weird gray area where the atom is in both or neither, and that causes its own problems.

But yeah, all these details were why I figured being able to re-activate dormant portals could cause issues. If you say that you can't, then you don't have to think about any of it. A portal is always in the same location as its original mirror-universe twin by definition, so you never have to worry about getting the position right.

Sure, that makes sense. Okay, I was confused about how you could have leeway in how perfectly the portals were lined up while simultaneously making it so that the portals could never change your position. This resulting-portal-is-the-intersection idea solves that pretty neatly.

Oh, interesting, that wasn't what I pictured at all. What about in the third dimension? Are these portals thin cylinders? I was imagining them as completely 2D circles, but obviously they'd never overlap unless they had at least some depth.

I see. Okay, that resolves most of my concerns. The last thing I was unsure about is how connected portals need to be in the same position in space. Does moving one cause the other to move even if the portal isn't open?

So okay, assuming that every universe gets doubled, then what happens in the following case: you open a portal, then close it, then open a different portal. Then you and your copy on the other side of the second portal both dial into the first portal. Does the one who finished dialing first get it and the other one doesn't work? Or does each copy end up dialing their copy of that universe? Either could be self-consistent - I'm just wondering which you had in mind.

(you know, in the version where you can reopen the portals)

I'm saying it's not just the ones you're connected to, but also the ones that were connected at some point and have closed their portals to you.

The reason is that otherwise, you could make infinite energy or money. Just copy yourself, hand yourself a dollar, then close the portal and repeat (hand your copy 2, then 4, etc.). Since the closed portals don't duplicate, the money grows exponentially but the number of people you split with grows linearly.

But anyway, yeah, the loopholes. So, keep in mind that I still haven't found anything in your system that definitely breaks, but some of it seems like it could be problematic. The main one is this: while you didn't say it explicitly in your summary, I have to assume that when you open a portal, you copy every universe that your universe has ever interacted with, including those that have temporarily closed their portals to you.

The main differences would be 1) risk (if something happened to the portal while you were in another world there would be no way back) and 2) portal uniqueness (there can only be one portal connecting any two worlds). So the latter means that you couldn't, for instance, pass through a portal at the airport, fly to another city in a parallel earth where the rate is cheaper, and then pass through a portal back to your earth once you arrive.

My idea had one significant difference from Vakus's version, though: in my version, you couldn't reopen portals that had closed. There was no "address" system - once a portal closed, no matter how you reopened it, it would just clone your current world, rather than bringing back the world that used to be on the other side. It's more limiting and depressing I guess, but it ties up a lot of loopholes which I think could be problems in Vakus's version.

So I figured I should say what my angle is, being the person who indirectly brought this topic back from the dead. Basically, I independently came up with essentially this exact idea, and found Vakus's post, and wanted to get the discussion going on it again because it felt like the question hadn't been explored that well before.