How far can space time be warped, twisted, and pulled?

Question

In the story I'm writing, an ancient civilization once roamed the local group, traveling from galaxy to galaxy with ease. Thousands of millennia after their disappearance, humanity stumbles across the last remaining ruin of their "network across the stars": an inter-dimensional mega structure known simply as "the bridge".

Placed between the Milky Way and Andromeda, the bridge is made of 2 main parts. On both ends of the bridge (one orbiting around Proxima Centauri, the other around a Black hole/stellar trinary system named Resurrect), there is a massive ring shaped structure known as a gate. When the bridge is opened, both gates will consume the energy of their host star in order to open up a black hole at their centers.

These black holes would then stretch through a dimensional subspace, known as scale space, in order to reach a tube-shaped relay station known as "The Nexus". Here both singularities are stretched into a ring shape and placed right on top of each other; creating a tunnel which turns the two black holes into one giant wormhole. From there, a ship could simply travel through one gate, pass through the Nexus, and emerge on the other side unscathed in a matter of minutes.

However, in order to make it as realistic as possible^‡, I was wondering if the bridge could actually work. Specifically:

• whether two areas of space time could be stabilized and connected together
• whether space time could be manipulated to accelerate and decelerate a spacecraft through gravity (so it wouldn't have to do a burn to stabilize its orbit once it reaches the other gate)
• If a wormhole like this would be safe enough to traverse. i.e., they wouldn't wind up spaghettified, incinerated, suddenly and abruptly vanished into thin air. and/or accidentally erased from existence.

‡(I need to use poetic licence on scale space, it ties in deeply to the book's main story)

Answer 1

This sounds like a complicated and overpowered version of an Einstein-Rosen bridge. Details about which can be found here. There are simpler and less overpowering ways to conceptually do what you want.

An Ellis wormhole with Gauss-Bonnett gravity, which for your purposes you locate in scale space, is recommended as it will give wormhole travel without the fear of spaghettification. It also does away with exotic matter being needed to keep the wormhole open.

The concept of stretching two black holes to form a giant wormhole is too full of unknowns to know whether it's conceptual feasible or not. It could pass the test of simply being a piece of scientific patter that sounds sciencey enough to provide all the rationalization your average reader needs to accept the concept. But if the two original black holes were rotating their combination, into a single black hole, might form a large Kerr black hole which might traversable.

There are two problems with black holes. One, once you've formed one how to get rid of it. Two, black holes are so 1980s science fiction. Basically stay away from black holes and go for wormholes pure and simple.

Answer 2

You're talking about a stable worm-hole, which is a great trope of space travel in sci-fi.

It can be found in Deep Space 9, the video game Mass Effect (which features ancient repurposed technology), and Stargate.

Your question is: How far can space time be warped, twisted, and pulled? And the rest of the questions have to do with probability of that given the science we know. Given that, the answer is no, but, framed the way you have, it can work, but the scientists don't really know WHY because it's borrowed from a much more advanced civilization.

Answer 3

As part of the fictional universe you’re presuming that it is possible. That is, it may be the real case that the topology of spacetime is strictly concerved, meaning it’s impossible to create any kind of wormhole that's seen by the bulk of the universe. Any singularity is hidden behind an event horizon, and short of creating a black hole first you simply can’t break space.

So answer 0 is that you “make it so” for your story’s universe. Now it’s just a matter of how much you want to explain it.

Just like magic, you run into less trouble if the audience is not given details of what’s under the hood. Anything you say may be shown to be wrong and well-known to future readers. Coming up with a complete self-consistent different universe is beyond our ability.

So «whether two areas of space time could be stabilized and connected together» is yes by narrative imparative.

«whether space time could be manipulated to accelerate and decelerate a spacecraft through gravity» a gravity drive is a different issue. A reactionless drive is strongly against fundimental principles of physics. But if you are bending spacetime, you can make a dip just ahead of the ship and fall towards it.

The technology is different though. Building a gateway is an external process that produces the gate’s ends. Warping space in front of the ship requires portable gear that operates on an area outside of the mechanism!

Why do you need gravity drives to jump through a wormhole? Any normal motion will do. You can install a cable car or magnetic rings or a moving sidewalk like you see at airports.

«safe enough to traverse» yes, if the splice points are spheres you simply need to make it big enough so you don’t feel tides from moving through the distorted region at the edges.

Current real scientific papers on wormholes indicate that it requires negative energy to hold it open. Basically take what’s “understood” about current physics and lampshade it with the technology of the advanced civilization or deliberate changes or extensions to the physics of your story’s universe.