[ST Ref: PT-B1-C5-A_220725: ‘Planetoid Trilogy’, ‘Star Island’, Chapter Five: “Another Paris Meeting”.]

#### Additional thoughts on Wormholes:

**SP:** I understand, Barrie, that you have had some additional thoughts on our last Wormholes post. Hence this post: ‘Wormholes revisited’.

**BC:** Yes, that’s correct, Ian. I was perhaps too reluctant to comment on a topic which is still very unclear.

**SP:** Unclear?

**BC:** Yes. Wormholes have been proposed from an interpretation of the general theory of relativity; a special solution of the Einstein field equations. But as far as I am aware there is no observational nor experimental evidence for their actual existence in the Universe. Wikipedia has an interesting entry on the topic of ‘Wormhole‘.

**SP:** So, because astronomers haven’t seen any and physicists haven’t reproduced them, you are skeptical?

**BC:** Exactly. But I’m neither of those professions and so I am reluctant to comment.

**SP:** So, why do you have additional thoughts on the subject?

**BC:** Well, since our last post on wormholes, I couldn’t get the topic out of my mind. Our last discussion lacked something.

**SP:** Hm, what did it lack?

**BC:** Some speculative thoughts. Specifically, a mind experiment.

**SP:** We lack evidence so you want to resort to speculation. Isn’t that rather pre-modern science? (smiles)

**BC:** I guess it is. But I prefer to think of it as more ‘science fiction author’.

**SP:** OK, so what is your mind experiment?

**BC:** Well, as I see it there are three possibilities.

**SP:** Only three?

**BC:** In terms of my mind experiment, yes.

**SP:** And they are?

**BC:** The first possibility is that wormholes do not exist and can’t exist, and that is why no one has found evidence for them. In this scenario, the maths is just that, maths. After all a mathematical model of something in the Universe is only ever a model. It is never the actual physical reality of that something, just our representation of one or more characteristics of it, presented in terms of mathematics.

**SP:** Hmm, some scientists may quibble with you on that.

**BC:** Yes, and in this particular case of wormholes, in all probability they would be right and I would be wrong. The specialists in this field are the experts, not me. I am expressing a layman’s speculative opinion, nothing more. However, it is my understanding that the experts are not in agreement over this matter.

**SP:** OK, what are the other two possibilities that you see for the existence or otherwise of wormholes?

**BC:** The second is that they do exist out in the Universe but they are difficult to see and we have just not found them yet. This could be because we do not yet know what to look for, or where to look for them. or that they are too small to see or are relatively invisible.

**SP:** And the third possibility?

**BC:** They exist, but are not in the arena of astronomers but in that of the particle physicist. They are subatomic in scale.

**SP:** Like in string theory?

**BC:** Hmm, maybe. But I am not a fan of string theory. Intuitively I don’t like string theory.

**SP:** But aren’t these fields of astrophysics and quantum mechanics inherently non-intuitive?

**BC:** Yes, and that is precisely why I was reluctant to talk about these three wormhole possibilities last time. After all, as a layman, what do I really know about this subject? Very, very, little. Consequently, I am talking now only as a science fiction author, not as an engineer, even though I am an engineer. And I am certainly **not** an astrophysicist **nor** a quantum physicist. If anyone reading this post can shed expert light on this topic, I invite them to comment with their insight.

**SP:** Yes, we invite comments from readers on this, and, indeed, any of our posts. But Barrie, you spoke of a thought experiment. So far you have only suggested three possibilities for the existence or otherwise of wormholes.

**BC:** Quite right. Well, the three possibilities are the set up for the thought experiment.

**SP:** Oh, and the thought experiment is what?

**BC:** Let us propose that wormholes do exist. Further, let us propose that one day someone finds or reproduces one.

**SP:** Yes?

**BC: **Depending upon where and how the wormhole is discovered, there now exits one single example of one. Having found one, scientist will now know how to go about finding more. After all if one exists, by virtue of the laws of physics of our Universe, there must be others.

SP: Couldn’t there be just one unique instance?

BC: Statistically, given the immense size of the Universe, this is extremely unlikely, to put it mildly.

SP: And if there are more?

BC: Well, if the conditions are easy for them to exist, they may be so common as to be common on Earth.

SP: But we don’t see them here.

BC: Right, although that may be because we have not created the right conditions for them to exist here.

SP: Or they don’t exist anywhere.

BC: Or they don’t exist anywhere.

SP: Are we any further ahead with your thought experiment so far?

BC: That depends upon the conditions existing where and when the first example is found, if it is found. Consider the common bar magnet. Without magnetic material, we would be blissfully unaware of magnetism. Faraday would not have been able to do his experiments and propose the existence of magnetic and electric fields. And Maxwell would have had no reason to devise his mathematical equations describing the action of electric and magnetic fields and their interactions. As a direct consequence, our modern world would not exist today.

SP: Is there, do you suppose, a material that exhibits wormhole like characteristics?

BC: Probably not. But there may be a combination of materials, when arranged in a very specific way, within a relatively complex experiment, that might. Who knows until it happens, either by design, or as the accidental consequence of some other complex experiment.

SP: Is this your thought experiment?

BC: It will do for the moment.

SP: Thank you, Barrie, it’s been interesting.

BC: Thank you, Ian, for being interested.

#### Acknowledgement to Wikipedia

Thank you to Wikipedia for the excellent articles that we have referenced in our post, above.