# Wormhole properties explained

• Writing: Input Wanted
• Michael27
The Shkadov thruster would be a good way to move a wormhole. In summary, the conversation discusses the concept of using wormholes as a plot device in a short story. The speaker acknowledges that wormholes require exotic matter or other means to stabilize them and presents various questions about their properties. They also mention the challenge of determining the position of a fixed wormhole and offer potential solutions such as using cosmic background radiation or fixing the distance between the two ends. The possibility of moving a wormhole using a Shkadov thruster is also mentioned.

#### Michael27

Hi
I am writing a short story about wormholes being used as a plot device.
I know wormholes have no stable solutions unless you put some form of exotic matter or other means of stabilizing the geometry. I assume that I have a wormhole of any size which is stable when other matter comes near it.
My questions are simple (but maybe not the answers):
• Does gravity affect a wormhole as in does a wormhole have mass?
• Is a wormhole fixed in space/time, example I have three wormholes (not connected) located in space time, do the relative distances/vectors change between the wormholes change because of the geometry differences of space/time at each location?
• Can it be moved by some means?
• If an object that is too large to enter the wormhole hit the wormhole what would happen to the object? Does the object break apart, just run past it, get a hole the size of the wormhole and only parts of the object will go through the wormhole?
Michael.

There are no confirmed scientific models to predict the behavior of wormholes. This makes your work as a sci-fi writer both easier and harder.
Easier, since you can set the answers of your questions according to the requirements of your planned plot. (Existing physics is a limit of course, but beyond that you are quite free.)
Harder, since once you established your universe you have to obey its rules, even if it ruins your plot later on... This is really hard, but also gives the most fun.

If you give us your own answers we might be able to point out flaws and requirements, but who would dare to set rules for the universe of somebody else?

I will try to explain how I see wormholes, or hope to use them in the plot:
• Is a wormhole fixed in space/time, example I have three wormholes (not connected) located in space time, do the relative distances/vectors change between the wormholes change because of the geometry differences of space/time at each location?
A wormhole is a fixed position in space time. This means that a wormhole would not be affected gravity or other forces. I ran into a problem here as determining the position becomes rather hard. Everything else is moving with some kind of vector through space but there is no absolute position, but by setting a wormhole to a fixed position in space time the wormhole will be hard to position.
• Can it be moved by some means?
Yes it should be able to move them but I don't know how.
As a wormhole is essentially an alteration of the geometry of spacetime, I need to find some way to make the mathematics work in spacetime.
I have two arguments:
1: Normally spacetime is affected by mass/gravity. A wormhole shapes the geometry in space. So it must show as mass, a very big mass as it bends space into a shape not normally considered.
2: Spacetime can have a geometry of its own. This can be a 'natural' geometry and therefore not caused by gravity. It simply is the straight path through spacetime.
How this can be accomplished is beyond me for now. I don't like to introduce exotic matter or some meta abilities that reach beyond spacetime. I don't have a good idea if the relocation of a wormhole would require energy and if so how much (only an order would suffice).

• If an object that is too large to enter the wormhole hit the wormhole what would happen to the object? Does the object break apart, just run past it, get a hole the size of the wormhole and only parts of the object will go through the wormhole?
When an object that is too large to enter the wormhole it will allow the particles that fit through and the rest to follow its normal path through space. This will make a very perfect round tunnel through the object. The wormhole is simply a path in spacetime but with the restriction that it will not fit anything as its geometry doesn't allow bigger objects to pass through.
Michael.

Michael27 said:
A wormhole is a fixed position in space time. This means that a wormhole would not be affected gravity or other forces. I ran into a problem here as determining the position becomes rather hard. Everything else is moving with some kind of vector through space but there is no absolute position, but by setting a wormhole to a fixed position in space time the wormhole will be hard to position
...

You can use the cosmic background radiation as stationary. That would be 630 km/s relative to the Milky Way. Alternatively you could use the Milky Way's center, The local group's center, or the Virgo super-cluster center. Might be simplest to put it in orbit around a star.

I assume a wormhole has two ends. One or the other could be fixed with respect to something. Or they could be averaged. Is there any reason why the two ends need to be balanced?

Rather than a fixed position you could set a fixed distance between the ends of the wormhole. As space expands the two holes would appear to fly towards each other.

Probably best to decide how the motion or position of the wormhole makes your story work. Then select the reason why that motion or position "needs to" have happened. Some of your characters understand the mechanics and the other ones trust her judgement.

Michael27 said:
Can it be moved by some means?
Yes it should be able to move them but I don't know how.
... I don't have a good idea if the relocation of a wormhole would require energy and if so how much (only an order would suffice).

.

Stars can be moved around with Shkadov thrusters.
For a star such as the Sun, with luminosity 3.85 × 1026 W and mass 1.99 × 1030 kg, the total thrust produced by reflecting half of the solar output would be 1.28 × 1018 N. After a period of one million years this would yield an imparted speed of 20 m/s, with a displacement from the original position of 0.03 light-years. After one billion years, the speed would be 20 km/s and the displacement 34,000 light-years, a little over a third of the estimated width of the Milky Way galaxy.
The main problem with Shkadov thrusters is that your characters usually die of boredom a few hundred thousand years before reaching the speed of a brisk walk. If you use an asymptotic giant branch star instead of the sun you can get 1000 times higher thrust. So walking speed in 10 generations or so. Shkadov thrusters are believable and do not violate any laws of physics. The wormhole is probably in orbit with the star so the thrusters have to move both.