# How does space between ends of a wormhole work?

I am writing up a system of wormhole-based gates to allow "fast travel" in a far-future setting. My description is an extrapolation of the way I understand a flatlander's experience of the following illustration of an Ellis wormhole:

Right now, there are the following specific questions that I am not sure about whether my interpretation is correct:

1. Am I correct that there is a maximum "aperture" width at the throat of the wormhole? And that a ship that was too big yet forced itself through would essentially fill the entire throat up, thereby "looping around" in this non-Euclidean deformed space within the wormhole and bump into ITSELF, crushing itself?
2. Am I correct that objects of sufficient hardness (ie. lack of elasticity) would crack/pulverize when forced through a wormhole due to the curvature of the space?
3. If so, would they "resist" going into space with increased curvature before they do? As in, would a diamond inside a ship passing through a heavily curved wormhole (seem to) respond to some force that stopped it from moving further without cracking? Ie. the diamond would start moving towards the back of the ship as the curvature of space pushed back against it harder than it did against the softer materials of the ship.

For completeness' sake, here is the full description as I have it planned right now.

A network of gates spans the known parts of the galaxy. These gates come in various sizes, but are consistently ring-shaped. The rings consist of ancient, self-powering, self-repairing technology yet to be understood by modern civilizations. The area circumscribed by the ring holds a spherical field that appears very much like a soap bubble, with various colorful distortions slowly drifting and mingling. However, unlike a soap bubble, one cannot see through this field; instead the opaque bubble acts as a mirror, showing a reflection of the surrounding space.

What we know of them is that they come in pairs (the matching gate is always of identical size) and function like wormholes. The space between gates features high levels of geometric distortion, but is otherwise safe to traverse without any special equipment.

Because of this geometric distortion, there is a maximum to the size of the ships that can use a gate (which is smaller than the size of the gate sphere). Think of the gates as entrances to tunnels, with the width of the tunnel at the narrowest part being the limiting factor. Of course, within this distorted space there are no walls as such, the tunnel walls simply represent where space starts looping around on itself, and a ship that is too big risks bumping into or even crushing itself.

The geometric curvature of the space between the gates has been and still is an important field of study to ensure the safety of inter-gate travel. Conventional spaceships and most lifeforms are usually not in any danger using a gate, but materials with very high hardness (diamonds and harder) have spontaneously pulverized when transported through gates with relatively high curvature.

As a general rule, the minimum size of a gate is defined by the minimum width of the tunnel and the maximum amount of curvature; the bigger a gate is, the wider the tunnel can be at the same maximum curvature, or conversely, the bigger a gate is, the lower the curvature can be when not changing the tunnel aperture.

The bubbles are theorized to modulate the size and curvature of, and hold stable the wormholes connecting them. Perhaps the civilization that created these gates had ways of changing these parameters of existing gates, but as far as is currently known, gates are static in curvature and aperture width. Inactive and broken gates have been found, some of which had tiny regular wormholes - lacking the distinctive bubble - at their centre.

• @AndreiROM I think you may be confusing wormholes with black holes. Wormholes a) don't suck things in, b) definitely DO have another side, and c) don't break things down into atoms. Black holes do all those things. Oct 26, 2016 at 15:01
• I think you are making a mistake by creating your gates and then fitting them to a theory, rather than starting from a theory and extrapolating to an idea.
– Kys
Oct 26, 2016 at 15:14
• There are many theoretical models of wormhole. Can't figure which one is closest to op's description. If he is using described one, posting a name and making description match well would make this answerable. If he is making it up, then sorry. Oct 26, 2016 at 15:15
• @Kys I am basically using this common graphical explanation of a wormhole and extrapolating the effects a flatlander would experience in that, to our 3-dimensional world. Oct 26, 2016 at 15:52
• Here's a very interesting simulation video of a wormhole transverse: youtube.com/watch?v=SZDOKtT_QZE Oct 26, 2016 at 16:52

The wikipedia article already shows a modelled Ellis (traversable) wormhole:

I must admit I would have problems to use that thing. :)

But essentially wormholes only exist in dimensions one higher than the dimension in it was created. That means the entry is not a 2D hole, but a 3D sphere, you can enter it from each direction and move out from each direction. Essentially it also makes much more sense than Hollywood wormholes like Stargate:

Because using a plane as separator forces a progression from one side to the other which asks the question how something which passes the barrier is not seperated immediately (one part is suddenly a world away). A correct wormhole has no barrier, you can enter and leave it continously at will.

It has boundaries which cannot be violated, so if something is too big, it won't get through (at least not without collapsing the hole). The tunnel itself consists of at least a 5-dimensional entity (yes, literally hyperspace) so if you are inside the tunnel, effects are unknown, but light and matter should pass through and also time is felt normally.

Forget only the thing with the space-time curvature. There is no effect on materials, remember the thing has one dimension more than normal (5-dimensional containing 4D space-time), so it does not restrict anything which is transported. Both ends could be on completely different sets of time and location.

While an Ellis wormhole does not show sign of gravitation because it was specifically constructed to do so, some other wormholes may not be so unforgiving. What a traveller may experience with the curved space-time in the transition zone which creates the dizzying effect is very strong gravitation. So once you get too near to other wormholes than the Ellis case, you will be sucked in literally. Depending on the size and dimensions it could lead to deadly spaghettification or only strong acceleration. The main problem of wormhole traversal will then to get out of the wormhole again.

• Thank you for linking me to the Ellis wormhole, it appears like my understanding is based on that model (whether correct or not). Ellis wormhole You are right, the entry would be a 3D sphere (as noted in my question). Am I wrong that if looking at the above graphic, there is a limited width at the narrowest part, one where a ship that is too wide would loop around the width of the tunnel and crush itself? Or are you saying that as well? What are you saying about the curvature? The way I see it, the inside of the tunnel would be non-Euclidean ie. curved. Oct 26, 2016 at 16:17
• It seems that I have given off the impression that the gates are two-dimensional. I initially did not include their description in my question because it seemed irrelevant, but here it is: "[The gates] come in various sizes, but are consistently ring-shaped. The area circumscribed by the ring holds a spherical field that appears very much like a soap bubble, with various colorful distortions slowly drifting and mingling." This "barrier" bubble is actually a forcefield that modulates the size and curvature of the wormhole, without it the wormhole would be tiny or completely collapse. Oct 26, 2016 at 16:40
• Actually, that last edit adds something incorrect. According to the wikipedia article; "The Ellis wormhole is the special case of the Ellis drainhole in which the 'ether' is not flowing and there is no gravity." There is no such thing as being sucked into an Ellis wormhole. Oct 26, 2016 at 16:47
• @Vaesper Oops, correct. Oct 26, 2016 at 16:56
• I believe the intent is that: the flexibility of your traveler/spaceship isn't at issue because from a 3D/4D perspective they are not being distorted. It's a bit like, if you have a 2D (3D with time) paper and send it through the mail in our 3D(4D) world, the journey it undergoes doesn't alter it in a way that it can measure from its own perspective. Oct 27, 2016 at 17:03

From the comments on the excellent summary answer by Thorsten S., it appears you still have specific questions: I’ll address just that, without going over the rest again.

It’s generally OK to work in a flatland analogy so you can visualize it and make physical models, as with your picture.

There is some question about whether the items in the space perceive the same curvature and distortion that you see from your hyperspace model. The answer is that it doesn’t have to be the same.

Start with a rubber sheet model of a plane. Draw your X-Y grid on it, and this becomes your metric. Roll up the sheet and the citizens won’t know or care. Stretch and distort the sheet, and it looks funny to you; but the metric is what controls the experience for those on the inside. Mr. A.Square’s rulers will stretch by the same amount, and he only cares about the passing tickmarks, not how they are seen by you. Picture looking at the plane through a funhouse mirror: it does not affect the plane itself.

Now if you made holes in the plane such that some gridlines were cut, they would notice that on the inside. If you distort the topology of the metric such that it’s not Euclidian, they would notice.

In the case of a wormhole, you have a topological feature which restricts how you can draw your metric. Approaching the bridge, you have a choice of having abrupt boundries where gridlines just end, or a hyperbolic geometry where parallel lines get squeezed together (the case you illustrate).

Yes an object can be too large to pass and will wrap around so that the right edge bumps into its own left; you could reach out and take our own hand.

Because of parallel lines converge (or diverge coming out) a ship will be squeezed and stretched as the ship’s sides, initally taking parallel tracks, are forced together. A large ship must travel slowly enough to deal with the resulting stresses, and perhaps be built with joints to absorb this!

• Excellent answer, it meshes with my mental model and even lead me to some new interesting thoughts. A possible solution for large ships which want to traverse relatively small wormholes - since the bigger the ratio of "object size"/"wormhole size" the more distortion an object will experience - is to have stretchable regions in the hull. One could envision armor plating in the form of scales that in normal space fit over eachother, but in a wormhole the "skin" holding the scales together stretches to accomodate the curvature. Also, only small diamonds could fit through without cracking. Oct 29, 2016 at 10:06
• A few (minor) things I am not sure on though. First of all, yes, it's true that one could theoretically stretch a rubber flatland in such a way that the metric is not distorted (uniform stretching in 1 or both dimensions, for example). Stretching and distorting it a la a funhouse mirror does constitute non-Euclidean geometry, though, if I am not wrong. Oct 29, 2016 at 10:07
• The alternative you gave of cutting gridlines; do you mean "stitching together" a wormhole-like structure from discontinuous pieces of locally Euclidean space? If we are visualizing it in 2D, this would be 2 flat pieces of paper with circular holes, connected by a toilet roll. Then, at the borders between paper and toilet roll, one would have a ring (in 3D: a sphere) of space with a huge negative curvature. Then again, you could make the holes and the toilet roll square and go through any non-corner area without problems. Seems a bit beyond the "reasonably believable" though. Oct 29, 2016 at 10:07
• Cutting gridlines: I mean this appears as a hard edge where space ends. Oct 29, 2016 at 19:17
• I was talking about the "Approaching the bridge, you have a choice of having abrupt boundries where gridlines just end" part, I mixed it up with the other one because I didn't realise you were not referring to the same phenomenon. Oct 29, 2016 at 19:53