# Gravity assisted travel along a Cosmic string

VSL (variable speed of light) cosmologists have theorised that Cosmic strings could be used as FTL highways for information. This is based on the theory that the speed of light was infinite at the birth of the universe and as inflation began, topological defects called Cosmic strings formed which still exist in our time and these strings contain compressed space-time where the speed of light is the same as the early universe, theoretically infinite or at least much higher than it is in our time.

This FTL theory is not part of my question as it speaks for itself and whether a worldbuilder wants to have a variable speed of light in their story. But this theory lead me to wonder about below speed of light form of travel using the gravitation field of a Cosmic string.

I am wondering if a ship could travel along a string in a spiralling motion using the gravitational pull of the string to propel it along. If we use the principles of gravitational assists from celestial bodies and possibly Penrose process for blackholes, if the cosmic string is likely to only pull a ship in a funnel shape spiral towards the string singularity then dumping some mass towards the string to propel out, although this method seems complicated and depended on the ship carrying mass to dump.

Preferably they could ride in a constant spiral without complications but what is the likely result if a ship tried this method and what would be needed for the ship to ride along it using the gravitational force of the string? If it is even possible.

• Do you have the science/tech to protect from tidal forces? - that's possible the key to doing it safely. Feb 6, 2022 at 20:07
• @EveninginGethsemane They are advanced enough that tidal forces at certain range should be no problem, I assume that a ship could spiral along it at quite a large radius from the string, so the forces should not be too strong. Feb 6, 2022 at 20:45
• Would need a lot more details about the nature of the physics near a cosmic string. If the speed of light is varying in the area there is every chance that getting close would radically change the nature of matter. Your ship might de-rez like the losers in the game grid in Tron.
– Dan
Feb 7, 2022 at 3:15
• In case people have forgottten what that looked like, start from about 2 minutes in to this vid. youtube.com/watch?v=m4cgLL8JaVI
– Dan
Feb 7, 2022 at 3:19
• @AlanDavies OK, but that's not what you ask for in your question. Can you edit your question to better explain exactly what you're looking for? (Never trust that people will read comments, always edit your question to improve it.) And please remember that you're bound to asking a single question (see the Needs More Focus close reason description). Thanks!
– JBH
Feb 7, 2022 at 12:51

I am wondering if a ship could travel along a string in a spiralling motion using the gravitational pull of the string to propel it along.

No.

Along the length of a cosmic string, the gravitational field is symmetrical, so the net force is zero. Radially, the gravitational force drops off as 1/r, so you don't get closed elliptical orbits--instead, you complicated rosette orbits. You can spiral your way along a cosmic string, but the string itself will provide no motive force.

You could generate energy by dumping mass onto the string, and use that to propel the ship... but that will use up fuel mass just like a regular rocket (although with much higher energy production per unit mass than any conventional rocket fuel).

• Thanks. I was beginning to think that nobody on this site could answer questions on cosmic strings, or, that they didn't want to engage in something so theoretical. A simple wiki search says my theory is wrong, theoretically? but it is always worth probing further and seeing others view on the subject. Feb 10, 2022 at 15:59

## How to navigate a cosmic string ?

When I first read your question, I visualized your science fiction string as some kind of cosmic rope I'm able to climb, with FTL speeds. Intriguing idea, but I think this is because of the word "string", which is a 2d object, providing a direction in 3d space.

You want a gateway, or tube or whatever you imagine to be a vehicle, something to carry you from A to B. You travel through it, or along with it.

Cosmic strings are different. Imagine a thread, 1 proton thick that can vibrate in 11-dimensional space, with 5-7 of its dimensions folded. You'll get a world with more than 3 degrees of freedom, more than 3 spatial dimensions. When you would be able to follow it, the string could lead you anywhere.

Add only a fract(ion)al dimension and you'll get lost

Now suppose you'd have a flatlander. A 2d-being. Put the flatlander on a fern leaf, which is a 2d fractal, that is an object with a fractal dimension, say 2.1 dimensional. The flatlander will start to travel until he reaches the edge. Imagine being in a very large room, with very complicated wands. A labyrinth. Eventually, the flatlander will be able to walk around this world, but it will take some time.

From 3 dimensions to 4 (or 5)

Imagine as a human, what a 4th dimension of space would do to your navigation. The string could disappear, when you're attached to it you will be translated into a different 3d world instantly. You'd have to find a way to avoid that, when you want to use the string to travel anywhere. A cosmic string is similar to the flatlander labyrinth, only worse.. Scientists do not know whether time (our 4th dimension) plays a role in cosmic strings. That would even more complicate "traveling along" the string.

My conclusion would be: you may be able to travel fast along a cosmic string, its multiple dimensions allow you to take shortcuts. The pitfall will be: navigation. Knowing where you are.

There are many theories around cosmic strings, you'll like the part with cosmic strings having negative mass. The above took some assumptions from Abelian Higgs, that is: cosmic strings and super strings have many things in common..

https://en.wikipedia.org/wiki/Higgs_mechanism#Abelian_Higgs_model