Have you ever wondered what it would be like to travel through space as if you are passing through a door? It takes a crazy amount of distance to pass through to travel through the magnificent cosmos, but what if you could warp space and time to let you pass through it? Well, if you have ever wondered or even are mildly curious about it, I shall introduce you to the profound worlds of wormholes.
Wormholes? What are they?
To start, what exactly are wormholes? Are they some kind of holes that worms travel through? Or something different? Well, the answer to the question is, they are not holes that worms travel through (although they can). In simple terms, they are an entity in space that warps space and time to allow them to bend those two for travel through space.
Wormholes are the solutions to Einstein field equations for gravity that act like a tunnel-like connection through spacetime, much like actual real tunnels created by worms in an apple. Scientists study the mathematical properties of spacetimes containing wormholes due to their unusual properties. The study of these strange geometries helps better distinguish the boundaries of behaviour permitted in the general theory of relativity. They could also, potentially, provide insights into effects related to quantum gravity.
In the simplest way, imagine you are holding a piece of paper that represents normal space. Think of traveling through space as traveling along the sheet of paper. Now mark a point at each end and bend the piece of paper in half, bringing those two points together but without letting them touch. If you were to travel in normal space (i.e. along the sheet of paper) the trip from one of your marks to the other would be longer than if there were a tunnel or a “wormhole” connecting the two points on the paper through the empty space between them.
In theory, a wormhole has two points connected by a “throat.” It provides the traveller could follow to get to a distant point. The path through a wormhole would be topologically distinct from other methods of travel the traveller could follow to get to the same destination.
Topologically distinct means that if an ant wished to crawl from one side of an apple to another, there are many possible paths on the surface connecting the starting point to the destination. These paths are not distinct topologically. Imagine that the ant instead crawls through a wormhole in the apple. A piece of string passing through the wormhole cannot be smoothly moved in such a way as to lie along one of the surface paths (or through another wormhole with the same end points but different route).
To picture a wormhole, imagine it as a tunnel that connects two points in spacetime. It could be a straight chute or more of a winding path. If a wormhole is traversable, it would act as a “shortcut” two points, that would, otherwise, be far apart. It could connect two points in a single universe or through different galaxies.
It is usually assumed that a wormhole in space-time, usually represents a shortcut, meaning that travelling through a wormhole, you could end up at a destination that would take lightyears to get to. This is usually found in science fiction.
Physics of Wormholes
Theoretical physics of wormholes, however, argues that there is no reason as to why the distance should be shorter. The distance could be a longer route, for all that we could know. To give an analogy, think of the long twisted holes worms sometimes leave in apples. The entrance and exit to the holes are much closer to each other on the surface than through the hole, that the worms bore through.
They can exist within any classical black hole solutions of Einstein’s equations.
When studying the mathematical solutions for black holes, the very first wormhole-like solutions were found. The solution lent itself an extension, whose geometric interpretation was that of two copies of the black hole. This was connected by a “throat,” known as the Einstein-Rosen bridge.
A throat is a dynamic object attached to the two holes that pinch off extremely quickly into a narrow link between them.
This was not the only solution calculated. They also found another solution that connected various types of other geometry on both parts of the black hole, behaving as “shortcuts” of spacetime. They found that this must mean that this solution could allow backward time travel! This theory implies back to the fact that if one could travel faster than light, they could communicate with the past. The time travel would lead to all sorts of paradoxical events.
The only problem? We have to now construct a wormhole that would allow for this to happen and I don’t know about you, but there haven’t been many wormholes showing up near my neighbourhood lately and they don’t seem very likely to show up any time sooner either. Another problem is also because they are not very stable either.
The only material which can be used to stabilize the wormhole is material that has negative energy density. No classical matter behaves this way, however, it is possible for quantum fluctuations in multiple fields to be able to.
Stephen Hawking theorized that while it may be possible for wormholes to be created, they can’t be used as time machines. Even if the exotic matter were to help stabilize them against its stabilities, he reasoned, inserting a new particle into it would quickly lose its stability, causing it to prevent its use. This is known as the Chronology Protection Conjecture, but there have been no such experiments done, to prove this (obviously).
Exotic matter is called “exotic” because it so little resembles all forms of known matter.
Not all hope is lost though. There have been calculations for another type of wormhole, called “transversal” wormholes. These wormholes exist in a wormhole spacetime, in which the wormhole is held open at least long enough for a signal or an object, like a spaceship, to pass through.
The interests in such wormhole solutions in general relativity were revived when Michael Morris and Kip Thorne of Caltech examined the general properties necessary for wormholes to stay open. They found that if a wormhole were to remain static and unchanging in time, it must have some kind of exotic matter in it.
Such exotic matter would have a negative energy density and a large negative pressure or tension. These would be larger in magnitude than the energy density.
All the forms of matter familiar to physicists and chemists have positive energy density (or, equivalently, positive mass), and pressures or tensions that are always less than the energy density in magnitude. No matter familiar is negative, as of now.
One possible source of exotic matter known to theoretical physics lies in the behaviour of certain vacuum states in quantum field theory. The possibility is the focus of most current theoretical research involving wormholes.
It seems to be difficult to put the quantum effects to open wormholes much larger than the characteristic length linked with quantum gravity, known as Planck length. Not only would it be useless for transporting spaceships, but it would also need quantum gravity to describe the hole if the wormhole was not much larger than this.
In very simple terms, quantum gravity is a field in theoretical physics that aims to describe gravity according to quantum mechanics.
In a research analysis of the behaviour of quantized fields in a wormhole spacetime, conducted by L.H. Ford and T.A. Roman, Brett E. Taylor, William A. Hiscock and Paul R. Anderson and others, it was shown unlikely that quantum field effects could hold open a macroscopic wormhole.
On the other hand, using approximate expressions for the quantized scalar field but having to make several assumptions concerning the unknown parameters of quantum gravity in their work, David Hochberg, A.D. Popov and Sergey V. Sushkov found a wormhole solution.
Currently, it seems unlikely that a macroscopic wormhole could exist in nature, however, there is still sufficient uncertainty in the argument, to allow theoretical physics to continue studying this intriguing aspect of spacetime. These are the hypothetical entities that show up in Einstein’s theory of gravity or the general theory of relativity.
Types of Wormholes
There are two main types of wormholes that have peaked the interests of physicists. They are called Lorentzian wormholes (general relativity) and Euclidean wormholes (particle physics).
Lorentzian wormholes are the ones that we so often see in science fiction. They serve as shortcuts through space and time. These kinds of wormholes are mainly studied by physicists, experts in Einstein gravity. If they were to exist in real life, these wormholes would more or less be similar to wormholes in Star Trek: Deep Space 9. There is good and bad news that comes from this solution.
The good news is that after about 10 years of research and an endless amount of hard work, we cannot prove that these wormholes don’t exist. On the other hand, the bad news is that these are very strange objects. If they do exist, they need a lot of negative energy to hold them open and keep them from collapsing on itself.
Negative mass is weird, but it is NOT anti-matter. It’s a region in space where the energy of the universe is less than that of an ordinary vacuum.
As of now, we can get small amounts of negative energy in a laboratory, the Casimir effect, however, getting it in large amounts is extremely difficult. On top of that, to supply enough negative energy to hold open a decent-sized Lorenztian wormhole seems to be hopeless, considering our current technologies. This does not mean it won’t be possible sometime in the future, just right now, our technologies are not advanced enough yet.
If Lorentzian wormholes do exist, we can easily turn them into classical time machines.
The other kind, Euclidean wormholes, are even stranger. They live in an “imaginary time” and are naturally a virtual quantum mechanical process. These kinds of wormholes are of main interest to theoretical physicists or quantum field theorists.
Imaginary Time is a mathematical representation of time that appears in some outlook to special relativity and quantum mechanics.
Physicists cannot give these wormholes a classical interpretation, in terms of a well behaved classical gravitational field. Unfortunately, we have to know a lot about quantum mechanics to even begin to appreciate even their basic properties.
Originally called white holes and since then changed to Einstein-Rosen bridges, theoretical physicists since the 1930s have hypothesized the existence of such shortcuts through spacetime.
Think of a white hole as the reverse of a black hole. They emit energy but do not allow anything to enter.
Wormholes are one of the most fascinating theories of the physics of the universe. Even if they seem to be something purely out of science fiction, that doesn’t mean they have to remain that way. Imagine sometime in the future, scientists announce that they have found a wormhole. How cool would that be? Imagine you could just go through a wormhole and you’d be millions of light-years away from home at your will and you could return whenever you wanted. Or maybe another, more advanced civilization than us, have already uncovered these secrets. Maybe they are on their way to us. There are a million possibilities that may be true so remember to always look up and wonder. Spend a few minutes looking at the heavens above and admire them. There are a billion possibilities out there and we are just reaching the tip of the iceberg.
- Wormholes are entities in space that warp space and time to allow them to bend those two for travel through space. They are the solutions to Einstein field equations for gravity.
- A wormhole is connected by two points connected by a “throat.” Although we mostly imagine wormholes as shortcuts, theoretical physics argues that there is no reason why they should serve as a shortcut.
- Wormholes need negative energy or exotic matter to stay open. A possible source of the exotic matter lies in the behaviour of certain vacuum states in quantum field theory.
- There have been multiple research done to study this. Studies have shown to have found two types of wormholes, Lorentzian and Euclidean.
- In simple terms, a Lorentzian wormhole kind of behaves like any wormhole in science fiction.
- In simple terms, a Euclidean wormhole lives in an “imaginary time” and is naturally a virtual quantum mechanical process.
About the Author
Hey readers! If you have made it this far, then I would like to thank you for reading my article! Hopefully, you learned something new from this article! I am super passionate about learning about new things, specifically more about space, astronomy and anything to do with space. If you want to read more articles from me follow me on Medium and connect with me on LinkedIn!