I'm on a Long, Narrow Road: What is a Wormhole?
- Mar 20
- 6 min read
Updated: Mar 21
Yes, I'm back with another hole that could form in this vast universe: a wormhole. But let me say upfront, whether wormholes exist in space is still a matter of debate because they relate to both quantum physics and general relativity. So they could remain theoretical, but they could also truly exist in the depths of space. Most of us know a little about wormholes, especially those who have seen Christopher Nolan's masterpiece, Interstellar: entering from point X in the universe and exiting from point Y via the shortest route. You can think of wormholes as using side streets to reach your destination instead of going all the way to the end of the main road. Now let's delve deeper and I'll answer your questions like "what is a wormhole?", "how do wormholes form?", and "are wormholes real?" with all my knowledge. Buckle up, because you might be pulled in another direction during our first handshake!
Contents
What is a wormhole?
A wormhole is a hypothetical structure that connects two distant locations in space-time. Wormholes could theoretically connect incredibly vast distances, such as a billion light-years, or as small as a few meters, or even different points in time or alternate universes. What we can say with certainty is that the length of the tunnel must be less than the distance between the two locations, making the wormhole a kind of shortcut.
Are there wormholes in space?
Since wormholes are still considered a theoretical structure by us, it is not known for certain whether or not they exist in space.
Types of Wormholes
Researchers generally believe there are six basic types of wormholes:
Passable wormholes: A wormhole that allows passage from one point in the universe to another.
Impassable wormholes: These are wormholes through which nothing can pass due to instability or the disappearance of matter passing through them.
One-way wormholes: A wormhole with a one-way passage typically describes black holes.
Two-way wormholes: A wormhole that can be used for both directions.
Intra-universe wormholes: Wormholes that open to two different locations within the same universe.
Interdimensional wormholes: A wormhole connecting to another universe.
How do wormholes form?
Currently, there is no realistic physical model of wormhole formation. The fundamental challenge is the requirement for negative energy density, which cannot be produced in macroscopic quantities. However, some scientists believe that wormholes could be constructed from quantum foam, a subatomic matter that can exist throughout the cosmos and is billions of trillions of times smaller than an atomic nucleus. But today, we do not have the technology to manipulate or detect quantum foam. I will explain this in another blog post, but in short, quantum foam refers to a theoretical view of spacetime at extremely small scales, supposedly composed of numerous small, rapidly changing regions. According to this perspective, at the smallest scales, matter and antimatter particles are constantly created and annihilated, forming a dense field of virtual particles.
What is the Wormhole Theory?
Now let's take a closer look at the details of the wormhole theory, which has cumulatively developed up to the present day.
Schwarzschild Wormhole
The concept of Schwarzschild wormholes, introduced by Ludwig Flamm in 1916, is based on the Schwarzschild metric in general relativity, which describes an infinite black hole. These wormholes are, by current understanding, impassable. They are inherently unstable and unsuitable for practical applications such as interstellar travel. While the Schwarzschild metric allows for the existence of wormholes, they are considered impassable and are generally viewed as mathematical artifacts or coordinate transformations within the metric context.
Some studies have explored the possibility of traversable wormholes based on mild generalizations of Schwarzschild wormholes, but these remain theoretical and require conditions such as exotic matter or modifications in general relativity. Exotic matter is a term used by physicists to describe matter that has unusual or "exotic" properties that do not conform to the behavior of normal matter. For example, matter with negative mass or mirror matter. Dark matter can also sometimes be referred to as exotic matter. The properties of exotic matter depend on the field of physics being studied.
Einstein-Rosen Bridge
The Einstein-Rosen Bridge is a Schwarzschild wormhole rediscovered in 1935 by Einstein and Nathan Rosen. Their initial motivation was to develop a more comprehensive theory of gravity and electromagnetism free from singularities. To this end, Einstein and Rosen aimed to eliminate singularities by introducing a new variable that represents a smoothed version of the Schwarzschild metric, creating a bridge or tunnel between two points in spacetime. In short, it's a shortcut connecting two points in the universe that doesn't destroy matter.
However, in 1962, John Archibald Wheeler and Robert W. Fuller published a paper showing that such a wormhole, if it connected two parts of the same universe, would be unstable, and light entering from the outer region would be compressed too quickly to reach the other outer region. They demonstrated that due to the compression of light, it would be impossible to pass from one end to the other. Remember, if any matter traps light, matter cannot exist there.
Travelable Wormholes
Although Schwarzschild wormholes are not traversable in both directions, their existence inspired Kip Thorne to imagine traversable wormholes created by keeping the "throat" of a Schwarzschild wormhole open with exotic matter. Lorentzian traversable wormholes would theoretically allow travel from one region of the universe to another within the same universe, or from one universe to another.
In general relativity, the possibility of traversable wormholes was first demonstrated in a 1973 paper by Homer Ellis and independently in a 1973 paper by K.A. Bronnikov. Ellis showed that the Ellis drain hole, by analyzing its topology and geodesics, is geodesically complete, horizon-free, singularity-free, and completely traversable in both directions. In mathematics, topology deals with the properties of a geometric object that are preserved under continuous deformations such as stretching, bending, crumpling, and warping; that is, without holes closing, opening, tearing, gluing, or passing through itself. Geodesy, on the other hand, is the science of measuring and representing gravity and spatial orientation in 3D, which vary over time.
A wormhole is a solution manifold to Einstein's field equations for vacuum spacetime. In physics, a manifold represents a concept that allows us to deal with different geometries outside of linear space. Ellis's wormhole solution depends on two parameters: “m”, which fixes the strength of the gravitational field, and “n”, which determines the curvature of its spatial cross-sections. When m is set equal to 0, the wormhole's gravitational field disappears, and a gravity-free, completely geometric, passable wormhole emerges.
What is the wormhole equation?
In 2013, Leonard Susskind and Juan Maldacena proposed the most natural process for the formation of a spacetime wormhole with the equation ER = EPR. This equation suggests a deep link between spacetime wormholes (ER) and quantum entanglement (EPR). The pair suggest that a wormhole (Einstein-Rosen bridge or ER bridge) is equivalent to a pair of maximally entangled black holes.
Are Wormholes Real?
Now, let's address the question of whether wormholes are real. Whether wormholes exist or not is not definitively known; they remain theoretical structures.
What happens if we enter a wormhole?
Many ideas have been put forward about passing through a wormhole, the best known of which are:
Appearing in a different region of space-time
Arrival in a distant place in the universe or in an entirely different universe.
Temporal displacement leading to arrival in a different time zone
Disintegration due to unknown or extreme conditions inside the wormhole.
Spatial distortion that potentially alters the physical characteristics of the occupant or their surroundings.
If the wormhole is unstable or leads to a dangerous environment, it may collapse or disintegrate.
Encountering exotic matter or energy and experiencing physical or temporal disturbances.
Time dilation effects, which cause subjective time to differ from external time.
Wormholes and Time Travel: How Possible Is It?
Time travel through a wormhole is theoretically possible. According to Kip Thorne, if one end of a wormhole reaches a speed close to the speed of light, a time difference will be created between the entrance and exit of the wormhole. As a result, one end of the wormhole will lead to the past, and the other end to the future.
Technically, you can also time travel through a wormhole within the same universe. How? Let me explain it simply: First, let's call the two entry points of a wormhole X and Y. Let X be in the Solar System, and Y be at the edge of the Observable Universe. When you enter through X and exit through Y, you technically travel to the future because an object there might still exist when observed from the Solar System. However, when you exit through Y, that object might have disappeared, and a new galaxy might even have formed in its place. Furthermore, if X and Y open into different universes, then time travel via a wormhole is possible. This is because these two universes might exist at different times, or time might flow differently between them.
What is the difference between a wormhole and a black hole?
There are major differences between black holes and wormholes:
Wormholes | Black Holes |
Their existence is purely theoretical. | Their existence has been proven. |
They connect two points. | Whether it leads to a specific point is unknown. |
It is unknown whether they can occur naturally. | How they are formed is known. |
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