When an event is labelled as a “play/ experience/ installation/ horror story”, it’s hard not to be intrigued. Trickier still when its organizers dare (rather than invite) you to take part. The event in question is The Mirror Trap, a one-person online show that took place in June as part of the Edinburgh Science Festival.

Adapted for the online space during the pandemic, the show is written and performed by Simon Watt, a science communicator who runs the stand-up comedy show The Ugly Animal Preservation Society and who has co-presented TV science documentaries including Inside Nature’s Giants. The premise is that Paul Gato, a quantum physicist, “has mysteriously disappeared, leaving behind a diary filled with ramblings and Feynman diagrams”, and that you have been invited to take part in his final experiment.

I’ve never been good at handling horror stories, but my curiosity overcame my apprehension and I joined online from my bedroom on the evening of 30 June. I was instructed to bring along headphones, a washable whiteboard marker and a mirror large enough to see my whole face.

When I followed the Zoom link, I was greeted with the familiar box saying that “the host will start the webinar soon”. I didn’t realize that I had been subconsciously expecting some kind of preamble until I and other audience members were plunged straight into the experience.

The only other character (besides you) in the show is Gato himself. You can’t see him (his camera is turned off) but, in any case, you aren’t going to be looking at the screen. Instead, he shows some Feynman diagrams and then tells you to pick up your marker and draw them on your own mirror. As he starts talking about the significance of the diagrams, he weaves in his personal backstory. But this is far from a dry physics tutorial – the idea of the show is that participants begin to experience optical illusions as they look in the mirror.

It is hard to add more without giving the game away, but suffice to say that the show is an immersive exploration of the spookiness of quantum mechanics and its various interpretations. While this is not untrodden ground in fiction, I found the show truly original in the way it paired physics with psychology.

One parallel that the play drew between the two sciences is the idea that we do not perceive reality as it is. We cannot properly comprehend bizarre quantum effects, as we are not adapted to perceive things on that scale. Similarly, illusions demonstrate that our senses are not infallible even on our own scale.

The show is minimalist and atmospheric. Watt delivers the narrative convincingly, with only an eerie background hum accompanying him. It’s an example of a Shepard tone, which sounds like it is descending in pitch infinitely, even though it is not. This again ties in with the fallibility of our senses, and also with the theme of infinities, which recurs elsewhere.

I didn’t time the show, but I would guess it lasted about 20–25 minutes. Watt then hosted a discussion with physicist Jenni Smillie and psychologist Kate Storrs (the experts are different in each post-show discussion), with the audience invited to ask questions. This is an integral and thought-provoking part of the experience. It is probably also necessary for many people as a way of “resurfacing” after any illusions they have experienced.

I’m glad to say The Mirror Trap didn’t trigger any disturbing visions for me (as I had been warned it might), but I found myself still pondering the meaning of the story days later.

I therefore spoke with Watt to find out more. Warning: this interview contains mild spoilers.

What inspired you to write this play?

Several years ago I heard about the strange-face-in-the-mirror experiment, where people see strange things when they look in a mirror for a long time. It reminded me of folklore and stories, from Alice Through the Looking Glass to the film Candyman. I later came across the “quantum suicide hypothesis” in the book The Never-Ending Days of Being Dead: Dispatches from the Front Line of Science by Marcus Chown, and I saw the film Kill List, in which one of the characters scratches an emblem in a mirror, and it gets horrific from there. 

I was also interested in how Feynman diagrams have this aesthetic quality to them, and they have a meaning reflecting deep forces of the universe. When you remove context, I think they look similar to occult symbols. These things rolled around into something, and my friend Alex Wood who is a fantastic playwright helped me refine it.

What were the challenges of incorporating an illusion that the audience participates in?

It has to be sufficiently long that the illusions take effect. They get stronger and the audience gets used to it, but it cannot be so long that people lose patience with staring at their reflection. Especially as the visual illusions could be at their most pronounced in the first minute or the 15th minute. It meant that the crescendo had to be in the story rather than in the special effects.

Genre-wise, the play is closest to horror. Did you set out to write a horror story, or was that choice dictated by the themes you were writing about?

A quote that has always stuck with me is “form is never more than an extension of content”. I make lots of things and some things feel like a sculpture, or documentary, or comedy. Hearing about a thought experiment where you kill yourself in lots of different universes is a horrific idea. Seeing monsters in the mirror also fits the horror genre. I mainly work in public engagement, and I think we have got very good at making science fun, which is great for young audiences, but people are more than just fun. There’s a whole rich tapestry of other colours we could be painting with. “Frightening” is one of them.

The play explores the interpretations of quantum mechanics, in particular the multiverse theory. Are you drawn to that one?

Not in the sense that I believe it’s correct or incorrect. I’m not qualified to make that judgement. I find the multiverse interpretation most fascinating because of how it led from Schrödinger’s cat to the quantum suicide thought experiment. I don’t think the other interpretations have led to anything weird like that. The other interpretations – that something happens and it collapses – are more vague. They don’t offer a compelling story. But I find them all interesting because they are not provable. I also find it interesting that these thought experiments were originally conceived to show absurdity, not to show that the idea was correct.

Your physicist consultant Harry Cliff said that nothing in the play is incorrect, but that he doesn’t agree with it. Did he elaborate on why or in what way?

He doesn’t like the multiverse theory because it’s an untestable thing. He finds the other arguments more compelling, partly by virtue of being more boring. The multiverse theory is a good story, but there’s a phrase that “science is the destruction of a beautiful idea by an ugly fact”. So therefore he’ll assume the ugly one for now.

The one-loop Feynman diagram is featured in the show. Why did you choose it?

It will probably seem arbitrary, but the main reasons are that I think it looks good, I like the symmetries it has, and the fact that it is a closed loop.

The show can trigger illusions and hallucinations in audience members. What has been the strangest reaction so far?

Normally about 10% of people see very little, about 10% see extreme things, and most people fall somewhere in between. 

The weirdest thing someone has told me after the show was that they saw the mirror bleeding. Lots of people have seen monsters, and at least two have seen someone appear behind them. It goes to show there’s a real phenomenon behind myths and legends.

It is left up to each audience member to decide what they think happens at the end of the play. Do you have a fixed idea of what happens?

I think that all of the possibilities happen. If the multiverse theory is correct, then all of them would be true. But it’s also an individual thing. In the same way that what everyone sees in the mirror is true for them, the ending that they believe is also true for them.

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In the play, the scientist seems to be driven mad by thinking about the interpretations of quantum mechanics. Is there a sense that it might be dangerous to try too hard to comprehend these bizarre phenomena?

That isn’t something I intended. The “scientist crippled by knowledge” is a common trope, but I try to avoid it because I don’t think most scientists are like that. A scientist could find out the theory of everything, and say “oh that’s interesting”, and then move on. I don’t think there’s very much knowledge that actually has a massive impact on personal philosophies.

I was talking with a friend who thinks it will change everything if we find aliens. I think it will change nothing, that we’ll say “oh there are aliens, oh cool” and then tomorrow’s news will come. The dark side of the play is the personal story – the content is about physics and psychology, but the story is about grief.

• The next two performances of The Mirror Trap are scheduled to take place in October, during the Swansea and Norwich science festivals (dates to be confirmed). The Mirror Trap is an ongoing project and Watt is always looking for people to collaborate with. If you’re interested in getting involved, you can contact him via his website