Types of wormholes

Based on the solutions obtained from the equations of General Relativity, there are two types of wormholes:

1.     The Schwarzschild Wormhole

The first type of solution would be present in the Schwarzschild metric having an eternal black hole, but it was found that this type of wormhole would collapse and destabilize too quickly for anything to cross through from one end to the other. The characteristics of this type of wormhole are very complicated to understand and therefore, I feel, are beyond the scope of this blog. 

2.     The Traversable Wormhole

Wormholes which could actually be crossed are known as Traversable Wormholes. These can connect and thus allow travel from one part of the universe to another or connect two universes. These can be created by holding the “throat” of a Schwarzschild wormhole open with exotic matter. Exotic matter is matter that has negative energy density.

The impossibility of faster-than-light relative speed only applies locally. Wormholes allow superluminal (faster-than-light) travel by ensuring that the speed of light is not exceeded locally at any time. While traveling through a wormhole, subluminal (slower-than-light) speeds are used. If two points are connected by a wormhole, the time taken to traverse it would be less than the time it would take a light beam to make the journey if it took a path through the space outside the wormhole. However, a light beam traveling through the wormhole would always beat the traveler. As an analogy, running around to the opposite side of a mountain at maximum speed may take longer than walking through a tunnel crossing it.

It is these wormholes that feature in sci-fi movies.

Introducing Wormholes

M

y last two posts were all about black holes and the so-called “applications” they may have. One of the central applications of a black hole is a Wormhole. Several physicists around the globe challenge the existence of wormholes simply because, at present, there exists no observational evidence, i.e. they have never been detected. However, some valid solutions of the equations of General Relativity do point to their existence. Hence, wormholes are often called the “Metaphors for teaching General Relativity”. You may ask, “How are black holes and wormholes related?” Well, wormholes are simply two-ended black holes.

The term wormhole was coined by John Wheeler in 1957.

Introduction

The meaning of the word wormhole is very literal. It has its origin in worms digging tunnels in the ground to traverse from one place to another. In physics, a wormhole is a hypothetical feature of space-time that is, essentially, a “short-cut” through space-time. Whenever a massive object, such as a star, blows apart in a cataclysmic explosion called a supernova, it gives rise to a black hole. If this black hole does NOT have a singularity that narrows to a point but instead has considerable space around the singularity, it is called a wormhole. This black hole would fall through to another location, which may be anywhere in the universe or in an alternate universe.

                                 

What one needs to understand is that wormholes simply exist in theory. No black hole has been observed to contain a “wide” singularity. And obviously, we can hardly hope to ever venture even close to a black hole to observe it. Therefore wormholes are purely hypothetical till date. As mentioned earlier, certain solutions of equations of general relativity do contain wormholes. Here again, we know nothing about their stability. Nevertheless, wormholes continue to be supported by theoretical astrophysics and are an object of fascination for many scientists.