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In my universe a 4th SPACIAL dimension exists around our 3 dimensions. I'm playing with ideas for a society that has access to a 4th spacial dimension and am currently thinking of what they would be able to construct. My thought process is this:

Say you are a 3D being and have a square 2D hotel in a 2D universe. You are thinking of adding an expansion but all available room near your hotel is occupied. So you build a whole new hotel and push it up one foot on top of your original hotel and install a way for the 2D people to move up and down between hotels. To them it would seem like they hadn't moved at all in 2D space and the hotel just changed around them.

Is it possible for multiple 3D buildings to occupy the same location in 3D space but be "stacked" in the 4th dimension? (Under the assumption a 4th spacial dimension exists around our 3D universe.)

Edit: Added emphasis on spacial because too many people think I am asking about a temporal dimension.

AJ D.
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9 Answers9

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Yes

It isn't any different to occupants of a 2D world asking whether - if there were 3 dimensions - could we stack objects on top of each other in a third dimension?

One thing to note, however, is that if the fourth spatial dimension exists then the buildings must have some size in the fourth dimension. As long as you space them accordingly along this spatial dimension - just as you would any of our three - then you can 'stack' the buildings in this way.

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Lio Elbammalf
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  • So in dealing with any further 4D construction, would it be accurate to imagine it one dimension lower (like my hotel analogy) and then extrapolate into the 4th dimension? Is it that analogous? – AJ D. Jul 17 '17 at 15:58
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    Yeah so you need your buildings arranged along the fourth dimension just as you would if your hotel was comprised of 2D floors but each floor was separated in the third dimension. – Lio Elbammalf Jul 17 '17 at 16:20
  • Re: "if the fourth spatial dimension exists then the buildings must have some size in the fourth dimension": Alternatively, the fourth dimension could be discrete; so whereas along our three spatial dimensions you can have something 1m away, 0.5m away, 0.25m away, 0.125m away, etc., this fourth dimension could have a fundamental unit and an item can only be "one slot over", "two slots over", etc. – ruakh Jul 17 '17 at 22:49
  • @ruakh Not if AJD wants it to work the same way as the three other spatial dimensions. – user253751 Jul 18 '17 at 00:40
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    @immibis: You don't say. – ruakh Jul 18 '17 at 00:45
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    Dont use any non allocated space in any dimension. It will segfault. – aloisdg Jul 18 '17 at 08:20
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    @aloisdg Or throw an exception, if it uses any flavor of managed God.NET. – Mermaker Jul 18 '17 at 17:37
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    This analogy already has real-world examples. Using time as the 4th dimension you have buildings stacked in the third dimension all over the place. – JBH Jul 18 '17 at 17:51
  • Well, you need a lot of concrete, because the wall between two stories in the fourth dimension means filling the 3D space completely. – Simon Richter Jul 18 '17 at 19:05
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    The mathematicians who live in a 2D world might be able to imagine "stacking" objects in a 3D space, but if they actually are 2D beings, how could they even exist in a 3D space? Think about this: What contains their guts in the 2D world? It's their skin (i.e., their perimeter), and the fact that there's no place else their guts can go. What happens to them when you suddenly release them from the constraints of their 2D plane and give them freedom to explore three dimensions? – Solomon Slow Jul 18 '17 at 19:05
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    @SimonRichter: That depends on how the senses work. If they have only 3D sight you don't need walls, just leave a gap. But on the other hand they need some way to "feel" the 4th dimension, or they would accidently kill themselves all the time. – Chris Jul 18 '17 at 21:08
  • @Chris We don't move a lot vertically, a person who can only see in their 2D view of the world may be able to move through a 3D world, oblivious of the upper floors, without accidentally moving upwards. Perhaps, similarly, it requires conscious effort to move in the fourth dimension. – Lio Elbammalf Jul 18 '17 at 23:51
  • @LioElbammalf: I agree with that. If they cannot move into the additional dimension that would be a boring story, so they need some sense for it or they need a tech gadget. My point was that if the privacy isn't affected, maybe you don't need walls. – Chris Jul 19 '17 at 08:09
  • @Chris Problem, if you just leave a gap between rooms in a 4th dimension there's nothing stopping things moving between those rooms. Wanna break in to a house? Just take a few steps in the w axis, walk in to the house, step back. Wanna confine heat? Better hope those pesky air molecules can't move in the fourth dimension then. – Kaithar Jul 19 '17 at 15:08
  • @jameslarge Not really a problem though, as the world already has the 4th dimension, and so there must be a 4th dimensional skin as well, just not one that can be perceived in 3 dimensional space. – AndyD273 Jul 19 '17 at 16:41
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    @AndyD273 that's the biggest problem for higher spacial dimensions really: it's an all or nothing proposition. Either everything exists with a size in the full dimensional set or you have to come up with an incredibly good reason why everything (after exclusions are specified) is confined to a single hyperplane. It's not that there aren't convincing reasons, like the 4D version of drops of water between two panes of glass, just that having such reasons cause as many problems as they solve. – Kaithar Jul 19 '17 at 19:00
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You are the master of your world, so yes. Some practical concerns:

Your guests are only three-dimensional and would like to stay that way. How do you get them from one "hyperfloor" to the next? Well, you put them in a "hyperelevator" and move the whole room across. Peasy, easy.

Are there alternate Earths under the other "hyperfloors"? You can answer that question both yes and no resulting in different problems. Yes can mean problems with the natives of those worlds. No means there is no gravity on those floors. And you will have to make things completely airtight, and either import or recycle oxygen. (Or both)

A related question is what is the view from the windows is like.

What do you do about power failure and fire safety? The "hyperelevators" are not running, the lights are off and the guests are panicking. Your move.

You need "hyperstairs". They will probably not look like ordinary stairs. The most reasonable look is a corridor that somehow starts on one hyperfloor and ends on another. Actually, you probably want something like that for water, waste and electricity too.

Just problematic is that power failure anyway? The "hyperstructure" of the hotel... is it something you build once and then it is stable, or is it something that is more like a force field that need continuous power to maintain? Your choice, but in the force field scenario you will need an UPS (Uninterruptible Power Supply) better than the Pentagon. I am talking Tesla Batteries and Diesel Generators and Cold Fusion Generators and exercise bikes with dynamos and ...

Finally, for marketing reasons you really need to find better words than "hyperwhatever".

Stig Hemmer
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    love the Hyperelevator - great stuff. – Fattie Jul 17 '17 at 12:40
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    I like this answer because it deals more with the practicality of it than with the sciency stuff. – Arturo Torres Sánchez Jul 17 '17 at 16:16
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    I wonder if one could build a "stairwell" that as well as shifting them along their normal three dimensions, could slide them along the fourth dimension as well. To them, they would see a lobby with like 3 stairwells, each stairwell takes them to the "above" five floors, but the five floors are different for each stairwell. Very practical and fire-safe. However, I make no claims about what someone halfway up the stairs would see when looking out. – Mooing Duck Jul 18 '17 at 00:56
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    I agree with @MooingDuck. For practical concerns, you better work out gravitational control, though. A better analogy than stacking two-dimensional planes is pushing slices together, since our gravitational vector is orthogonal to the 4th dimension. Imagine a two-dimensional world with gravity, something like this. Now imagine extending that into the third dimension. Now imagine various ramps and so forth between the "slices." You have your hyperhotel. – Wildcard Jul 18 '17 at 03:11
  • @Wildcard I have been trying to wrap my head around the gravity situation as well. My thought was that our 3D universe is actually a crinkley 4D hyper-torus. The "crinkles" are valleys in 4D space, which is perceived as gravity in our universe. See Riemann's Bookworms. But you are saying that gravity in 4D would be perpendicular to gravity in 3D. Could you explain this a little more? – AJ D. Jul 18 '17 at 13:39
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    Also consider that if there's a device able to rotate things through the 4th dimension, it's possible to effectively mirror people and objects. So someone who's right-handed could go through a 4D turntable and come out left-handed. From their POV it would appear as if the rest of the universe got mirrored. – Kyle Jul 18 '17 at 13:53
  • If the 4th dimension is small (say, a few mm or nm), yet 3 dimensional structures are stuck on layers in it (branes) and gravity crosses between them, then we'd have gravity. Native matter in the other branes might weakly interact, creating weak gravitational effects on sub-galactic scales. We push our matter into the other brane, and it retains its properties. Suspending the hotel so it doesn't fall into the rubbish heap at the other-brane Earth core will require work, but gravity won't be a problem. – Yakk Jul 18 '17 at 14:21
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    @Kyle there are some interesting and subtle problems with that, such as the structure of protein molecules, all explored very nicely in Roger Zelazny's Doorways in the Sand. – Wildcard Jul 18 '17 at 15:33
  • @AJD. That's not quite how general relativity works (though it's certainly often depicted that way), and wouldn't be compatible with your idea anyway - you're only considering the hyper-surface of the hyper-torus, which doesn't allow "stacking" - there's only one possible value for the fourth coördinate. If you extend this fourth dimension, you need to explain where the gravity goes - or rather, why it doesn't get lost in the extra dimension (remember the inverse cube law? If you take the string-theory approach (the other dimensions are very compact), how do you make them "bigger"? – Luaan Jul 18 '17 at 15:36
  • @Luaan just for clarification I wasn't saying our actual universe functions like the hyper-torus I was thinking of my fictional universe's layout and how that would work. Ive done research on higher dimensions, but only for the vectoral aspects of them. Could you link some reading material for the string theory approach? – AJ D. Jul 18 '17 at 15:48
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    @AJD. You can find good quick introductions all over the internet, just search for "compact dimension". I quite like Luboš Motl's approach (somewhat above the usual pop-science level), and he has a nice intro with a lot of surrounding context (still quite high-level, mind you) here - http://motls.blogspot.com/2010/11/extra-dimensions-lhc-and-real-world.html. He explains many consistent models of extra dimensions in our reality - you can take some inspiration there; they're probably all too limiting for your story, but that takes just one small hand-wave and a bit of care. – Luaan Jul 19 '17 at 07:21
  • Whether or not you need stairs to access the "compartments" along the W-axis would depend entirely on the direction of gravity in 4D space. – Draco18s no longer trusts SE Jul 20 '17 at 15:00
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Initially consider it as time.

There was a building before the one you're in and a building after it. All you need to be able to do is move between those buildings.

Consider a co-ordinate system x,y,z,t. x and y are the ground level, z vertical and t your 4th.

Just as you move between your building and the one next to it, which shares your x,z,t co-ordinates, by moving in y, you can move in your 4th dimension between the buildings sharing your x,y,z co-ordinates by moving in t.

The only problem is moving in that 4th dimension when you only exist in 3.

There can be an indefinite number of stacked Flatland planes of existence, none of them are aware of the others, none of them can interact with the others or pass between them. They exist only in x and y, they have no z and no understanding of z.

But

There's always a but. Your society has a 4th spacial dimension, so they'll use it as a matter of course. Flatland has no access to the 3rd dimension so you can stack Flatland planes without a second thought and with no issues. Your society is going to have buildings that already exist and have length in this 4th dimension, you can't just casually stack them like 2D worlds in 3D, you'll have to put them alongside each other. You'll also have to work out terminology and decide whether like left and right, you can just go that way or whether like up and down, it has a force and you need to have something to support you in "flight".

Going back to the example of time as a 4th dimension, while we can't control our movement a building still has a length in time. A building may be 10metres x 5metres x 20metres x 100years, but they still exist and have a fixed length in that dimension.

  • Time has a "force", it always draws us forward (like gravity pulls us down)
  • We can't travel against the force without assistance (which we haven't developed yet)
Separatrix
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    This reminds me the "structured reality" of Vonnegut's Slaughterhouse 5 – L.Dutch Jul 17 '17 at 07:27
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    The question does specifically say a spatial dimension. Using time adds the problem of the buildings moving in time as they age - they don't necessarily move in the spatial dimension. – FreeElk Jul 17 '17 at 08:19
  • @FreeElk, I used time as an example that people can understand, very few people can imagine extra spacial dimensions, but the use of time as a replacement helps that understanding – Separatrix Jul 17 '17 at 08:23
  • Maybe its just a hang up I have but when I think about things beings separated in time I just wonder what happens when the two times join up - this isn't a problem you have in space unless your buildings are on wheels. – FreeElk Jul 17 '17 at 08:32
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    @FreeElk, usually someone turns up with a bulldozer ;) There are a few meters between buildings in x and y and a couple of months in time. The gaps are measured in whatever units you use to measure that dimension. – Separatrix Jul 17 '17 at 08:35
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    Using time as an example just makes it more confusing, because when you move through time, you still exist in the other times - i.e. if you travel back in time, you would run into yourself. This is not a problem with a spatial dimension, as no matter how you move through the 4th dimension you won't meet yourself. – Benubird Jul 17 '17 at 09:37
  • @Benubird, you have a point there, but I'm limited for options unless you have a suggestion? – Separatrix Jul 17 '17 at 09:39
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    The trouble is that as 3D beings it's very difficult for the average person to comprehend a direction which is at right angles to all three of the spatial dimensions we know. Hence using time, it's imperfect but at least you can wrap your brain around it. – Joseph Rogers Jul 17 '17 at 09:46
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    +1 for mentioning that if the beings already have access to a 4th dimension, then they're probably already using it. I guess there could be cost/technology barriers that discourage using the 4th dimension, though (we don't all live in skyscrapers, even though we're able to build "up") – A C Jul 17 '17 at 18:10
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    @JosephRogers I disagree, even if nobody can comprehend 4D, everyone can comprehend the Flatland analogy and use it to work out the mechanics. – user253751 Jul 18 '17 at 00:44
  • @Benubird "if you travel back in time, you would run into yourself. This is not a problem with a spatial dimension," I disagree. I can totally clap my hands. Which is one hand moving forward in a spatial dimension and the other moving backwards until they run into each other. – Mooing Duck Jul 18 '17 at 00:59
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    @MooingDuck, can you clap one hand? – Wildcard Jul 18 '17 at 03:07
  • Comprehending what it would look like to move in 4 dimensional space isn't terrible, for a starting point just close one eye and try to pick up a hair. The issue is that the flatland stack isn't a valid analogy any more than thinking of it as time is, both imply that stuff has a zero width in extra dimension. That's where the problem of being at right angles to the (x,y,z) comes in, you have to handle the appearance of something with a hypervolume of (1,1,1,1) being offset by 0.5 in the w axis. In reality it would have a uniform 50% "concentration". – Kaithar Jul 19 '17 at 19:21
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Really it depends. Let's consider the fourth dimension to be a spatial dimension perpendicular to all other three spatial dimensions. The main problem will be this: does gravitation extend into or along that fourth spatial dimension?

If gravitation is fourth dimension, and unless the stack of buildings isn't secured, the stacked buildings will fall down, in the direction of the fourth dimension, and crash into the buildings stacked in the other three spatial dimensions.

This might look like the buildings in three dimensional space inexplicably undergoing massive damage and deformation, apparently without a cause (as the stacks of buildings falling down in four dimensions won't be observable in three dimensions).

This suggests you should four dimensional gravitation out of it. In which case, stacking extra buildings in four dimensions may be fine.

Lio Elbammalf
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a4android
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    Gravity only applies on the axis inline with the force, it doesn't apply on the other perpendicular axes. The 4th dimension may have its own force, but it won't be gravity. – Separatrix Jul 17 '17 at 14:05
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    Stacked in the "other three" spatial dimensions? That's not how it works, you don't get to choose a dimension. – user253751 Jul 18 '17 at 00:45
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    @Separatrix what does "the axis inline with the force" mean? – user253751 Jul 18 '17 at 00:45
  • @Separatrix, so what do you do when your 3-dimensional guests walk "down" your 4-dimensional emergency exit ramp back to their normal 3-dimensional plane, but momentum keeps them moving just a little bit too far? Whatever else you have, you would definitely need some fine-tuned control of gravity, or some extremely clever engineering work. – Wildcard Jul 18 '17 at 03:06
  • @Separatrix if gravitation acts in all three 'normal' spatial dimensions, then why should it not act in the fourth dimension? It's easier to assume that it does than that it doesn't. – a4android Jul 18 '17 at 04:01
  • @immibis If the fourth dimension is perpendicular to all three spatial dimensions, then there will be stacks of buildings in the fourth dimension relative to them along each of the three dimensions. – a4android Jul 18 '17 at 04:04
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    @a4android, gravity acts along the z (vertical) axis, x,y and '4th' are all perpendicular to this. There's no reason why gravity should act any differently in 4th than it does relative to x and y i.e. it acts only in z. Flatland has no gravity because it has no z. – Separatrix Jul 18 '17 at 09:32
  • @Separatrix Flatland has no gravity because its author didn't think of adding it. If it had curvature there would be Flatland gravitation. It is the lack of gravitational potential along x,y that it seems gravity doesn't act. Gravity will be present on all 4 dimensions. The issue is whether there is gravitational potential. If the '4th' has, things can fall '4th'wards. – a4android Jul 18 '17 at 09:48
  • @a4android, I think we'll end up arguing at cross purposes here, but yes. I say only in z because in a gravitational field it's conventional to align z with gravity and hence be able to ignore it in all other axes. – Separatrix Jul 18 '17 at 09:54
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    @Separatrix That's a reasonable way of looking at things in three dimensional space. The difference is I am prepared to entertain the idea that gravitational field effectively acts along the 4th dimension. Your approach is equally reasonable. It's the deplorable lack of 4d structures that prevents us from testing our ideas. It's all the fault of the universe! – a4android Jul 18 '17 at 09:59
  • @a4android If gravity acted in the fourth dimension, the inverse cube law wouldn't work for it. The same problem applies to electromagnetism etc. You need some mechanism that keeps everything in "our" 3D (sub-)space the same, while allowing an extra spatial dimension we do not perceive. It's trickier than it sounds, and there's quite a bit of sci-fi that has seriously investigated this in the past. Can you rotate a human along the extra dimension? If so, you could turn him inside out (possibly without killing him). And how would gravity interact with him then? – Luaan Jul 18 '17 at 15:43
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    @Luaan I think you inverse square law. But you have raised a good point. It fixing the problem may be easier. Assume 3D space has the same physical properties of gravity & electromagnetism, then adjust the gravitational constant & possibly values for charge. Allow the extra gravity & EM forces to propagate in the '4th'. That's off the head reasoning & probably wrong. Anyway it's thought gravity is a weak force because it leaks out of the brane where our spacetime is located. – a4android Jul 19 '17 at 01:41
  • @a4android The problem with tweaking the constants is that they don't affect the falloff. What you'd need is to replace the gravitational constant with another function, which happens to coincide with the gravitational constant in all our current observation. One possibility is that the fourth spatial dimension isn't infinite - it doesn't expand with the universe. Even better if it's extremely small (e.g. as some serious theories suggested, it might only extend a Planck length or so), and can be locally expanded. Even better if you can actually make it consistent with e.g. dark matter :P – Luaan Jul 19 '17 at 07:26
  • @Luaan For this question it was reasonable to assume the 4th spatial dimension was similar to the other three. String theory compacts all other dimensions. My ideas were first thoughts & easily wrongheaded. A non-expanding 4th dimension could have interesting properties. Locally that shouldn't be a problem, but cosmologically things could get funny. – a4android Jul 19 '17 at 11:27
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A good use for 4D would be to house a 3D prison. In 4D space you can achieve a vantage point where you can see all 3D points simultaneously, with no occulusion from walls. Similar to how if you stand in 3D above a 2D sheet of paper you can see the whole thing, irregardless of how many lines are on the paper that would block the view of 2D beings on that paper. While a 3D being might not be able to achieve such a 4D vantage point, they might be able to create a camera of sorts that can.

As for hotels, as hotel rooms are independent of one another (ie you don't need to see the contents of one from another) all you need in 3D space is reception, an elevator and a single hotel room. The button in the elevator room transfers the elevator to a different 4D plane to face a different room. In any 3D instance this makes your hotel very small, no need for separate floors, but it can support infinite rooms. I'm trying to figure out if the elevator room could simply rotate in 4D space to face different rooms instead of translating, might be safer or more energy efficient.

Weyland Yutani
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    This is assuming that light casually leaves 3D space so you can see it across all four dimensions, meaning that from our perspective, all objects rapidly lose heat and energy, and even in a vacuum light is lost from a source. I think it would be a bit of a plot hole for that to be the case. – Harmless Jul 17 '17 at 21:24
  • This also assumes that there is relatively no energy cost in moving between planes. It might actually be cheaper to build many rooms than the energy requirements to move between planes. Granted, using something like an elevator paradigm there isn't much difference. But using something like a portal paradigm, the person moves from the lobby (filled with portals) and steps into a different universe. – Phil M Jul 18 '17 at 00:19
  • Even better for the prison - you don't need to have any paths out of the rooms in 3D until you actually need to interact with the prisoner. Then just do a bit of four-rotation, and get access to that particular room temporarily. Good luck trying to dig your way out of that with a spoon! :P – Luaan Jul 18 '17 at 15:47
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No

Unless you just handwave everything, there is no physical sense to viewing any spatial dimension "different" from any other, or to be able to travel "through" an additional dimension.

Flatland is a great example. If you take a Flatland style piece of paper (2D) and a second piece of paper, and put them on top of each other, you do not get 3D space. Topological, you are still locally 2D with some weird effects like being able to "tunnel through" between the sheets of paper by making holes and glueing the edges together, or forming a donut out of a single sheet by glueing opposite edges, or being able to flip beings by glueing a band of paper in the Moebius configuration.

You can do a little experiment: Take a sheet of paper (15x15cm in size) and draw a 10x10cm square on each with a pen. Make it one of those pens which "bleed through" the paper, and thin paper. So it seems like the drawing is really "inside" the paper, just like a Flatlander would be. Now stack many of them, until they build a 10cm high tower. You now have a 10cm high tower of 2D sheets, but what you do not, in no fashion whatsoever, have, is a 10x10x10cm 3D cube.

Thinking the other way round, no 2D Flatlander could ever "lift off" its universe to travel through 3D space, in the same sense that you could never lift off a pencil drawing from its sheet of paper. The operation would just not be defined in any useful mathematical or physical sense.

Our (real) 3D is fundamentally different from a hypothetical 2D stacked upon each other. Even if you take our greatest microscope, at no time does anything fundamentally behave in a 2D way.

A more mathematical way to see how this does not make sense is to see that all dimensions (to be called dimensions in any way making physical sense) would have to be continuous. The stacking 3rd dimension would be discrete and thus people would probably not even call it "space".

All of this scales up seamlessly to 4D.

Bending

What you absolutely could do would be to bend 3D space in creative ways. This is 100% compatible with our real world, as far as we know. This is what happens in the Flatland example, of course - stacking two sheets of 2D paper on top and glueing them is just an easier to imagine way of having a single 2D space in the first place and bending that one into a stacked configuration.

But you cannot have a (physically working) 4D space somehow "embedding" a 3D space and having meaningful travel for the 3D objects.

Multiverse

Your stacking version could also just be a multiverse as we are thinking about today. Those are perfectly happy (and basically required to be) stacking/discrete. But don't call them 4D please, either.

But...

...you can also just forget everything above, you have artistic freedom. It would just grate hugely on everybody who has a passing intuition about these things, spoiling suspension of disbelief absolutely. The broad masses won't probably notice anything, I guess. ;)

AnoE
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As you said it can be visualized as going from a 2D world to a 3D world : everything needs a depth in the new dimension.
To stay with the 2D/3D analogy, your squares have to become cuboids. As you can stack many slim cuboids in a cube, you can stack many 3D hotels in a 4D hotel as long as they have a very limited depth in the 4th dimension.

Note that one tricky thing is to help peoples turn along the new dimension in order to get from a 3D hotel to another... There is a game demonstrating the concept, Miegakure, I believe their videos makes the possibilities quitte clear.

Nestor Demeure
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    If you could flesh this out a bit more it would look more like an answer. As it is now is more of a comment and might be deleted as such. – L.Dutch Jul 18 '17 at 09:41
  • Wekcome to Worldbuilding SE, NestorDemeure, I agree with L.Dutch your answer needs more substance and should address the question. Answers should ahve facts, information, and reasons to support explanations. Have fun here! – a4android Jul 18 '17 at 09:54
  • I agree with you, given more reputation I would have just posted the link in a comment. I added matter to my answer in order to improve it. – Nestor Demeure Jul 18 '17 at 10:23
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Imagine putting multiple flat squares on top of each other. You end up with multiple squares in the same 2D space by stacking them in the third dimension. What you are proposing is identical but going from the third to fourth dimension. The limitation you face is that perception or travel in a fourth spatial dimension is not currently possible.

So, in answer to your question: is it geometrically possible? Yes. Is it physically useful? No.

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I have a problem with the answer(s) in this question, even though being an answer I thought of aswell

I'm no expert but quickly I think "yea! you can have a building in one spot, then another in the same spot but in a different time period, and have a 'transportation' device to move between them"

Buut

If we place a building in a spot, then by accessing the 4th dimension we put another building in the same spot but 5s later, what happens once the first object meets the other? Will they crash? An object will suddenly appear where the first was.

You could have buildings be separate more time, like 50 years from one another, but still. I think eventually the buildings ahead of time would have to be destroyed before hand. Placing buildings in the past would cause the same issues. It wouldn't be handy to have whole buildings I guess but rather solo rooms, easily destroyed before the 'crash'

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    Hi, yeah that is a problem but this looks like a comment on other answers rather than an answer to the question. The question does specify an extra spatial dimension. – FreeElk Jul 19 '17 at 19:02