by Noah Levin
Witnessing a monumental change in history is equal parts frightening and fascinating. Hannah and I were among the privileged few to have front-row seats to the biggest revelation humanity would uncover in our lifetimes. The world’s greatest minds are still grappling with what it means, but I already know the answer they are reluctant to accept.
“You’re serious? You think that we’re living in a simulation?” Hannah asked.
“What else could possibly explain it? We both saw the double-slit interference bands disappear with our own eyes. How could something like that change if we’re not in a simulation?” I replied.
It was a bizarre and very specific thing that changed, something that one would only have observed by doing certain classic physics experiments at the exact right moment.
Hannah did not agree. “I saw the same thing that you did and I have no idea why it happened, but I just don’t see why it means we’re in a simulation.”
“Let’s recount what occurred. First, the problem: quantum physics is weird as hell and particle-wave duality is the weirdest of all. Sometimes light acts like a wave and other times it acts like a particle. This is what we were looking at, right? So we started by shining a laser through some very narrow and very close slits. And what did we see?” I asked.
“Come on, I was in class with you. We don’t need to go through this step-by-step.”
“No, we do, so you can understand why it means we’re living in a simulation. We saw a particular interference pattern caused by constructive and destructive interference when we first shined the laser through the slits. What was it?”
“Double-slit interference, which looks like a row of parallel lines that grow darker and lighter like little hills until they fade away.
“And why is that unexpected?”
“At first, it doesn’t seem like there’s anything wrong. The light is traveling through two slits and the waves are interfering with each other as they should be. But the problem is that since light is a particle and the lasers we’re using send out one photon at a time, each photon from the laser should only be able to pass through one slit, but they’re all acting like they’re passing through both slits. Hence the interference pattern.”
“And if we stop and ask the photon which path it took, the interference pattern changes. It goes from all those thin lines to blobs.”
“Which is what we would expect from single-slit diffraction when it passes through just one slit. The photons in the laser act like they take both paths until we ask which one they’re taking and then they really do only take one path. Observing the photons changes the behavior of the system.”
I corrected her, “We can’t say that. Observing one part of the system changes what we observe in another part of the system. We don’t know if anything is behaving any differently, we just know we’re seeing different things. And what happened yesterday? Right before our very eyes, double-slit interference changed into single-slit diffraction and the lines became solid blobs. The photons were no longer behaving as if they took both paths but were acting like they were taking just one path.”
When it happened, we both thought we had screwed something up in our experiment and our two slits had become one or we had bumped our setup, but the same thing happened to everyone in the class.
Hannah replied, “Okay, but I don’t see why it means that we’re in a simulation if the universe changed—”
“Not so fast! We can only say our observations of what we experience as our universe changed. We don’t know if anything actually changed. It’s just that double-slit interference now looks like single-slit diffraction.”
“Okay, Mrs. Technical, our observations changed. But why does that have to mean we’re in a simulation?”
“Because there’s no other explanation for it.”
“Shouldn’t we have some other reason to think we’re in a simulation? You can’t just take one piece of evidence and draw a conclusion from it, especially such a big one. Maybe God did it? I know you’re basically an atheist, but you can’t rule that out. You need more to go on than just what happened yesterday. If double-slit interference was so weird in the first place, maybe we still don’t understand it, so perhaps it can just disappear. I remember Dr. Danet saying that Richard Feynman called double-slit interference ‘the only mystery of quantum physics.’”
The mention of Dr. Danet’s name made me immediately recall the emotions in his face that had been burned into my memory. When we all told him what we observed, he went from shock to disappointment—at his students for thinking they screwed up the experiment—paused for a brief moment at understanding, and finished with fear. He ran out of the room in disbelief and straight into Dr. Chambers who had been teaching the same lab next door. His knees buckled when he saw that she looked just as broken as himself.
I pushed his face out of my mind. “The whole point of doing the experiments yesterday was to see that quantum physics is unintuitive. And now that double-slit interference has inexplicably changed to do something a little more intuitive, it shows that it wasn’t supposed to be there in the first place. Nature doesn’t change, but computer programs can.”
“You act like you understand how this all works, but we don’t. How can you be so sure that double-slit interference can’t suddenly change?”
She had a point, but I was ready for her.
“Because the existence of this phenomenon in the first place was evidence that we’re in a simulation, we just didn’t want to admit it. Look how weird it all was: photons seem to interfere with themselves even though they can only take one path. How do they—sorry, how did they—do this? Why did they do this? And they only did this as long as we didn’t ask which path they took? If we ever had a way of finding out right where the photon was at any moment, then the double-slit interference pattern would disappear and the waves collapsed to a point and did the intuitive thing of traveling through a single slit. This stuff never made any sense since it just doesn’t fit with everything else we understand about physics. But it can make sense if we are in a simulation. The only conclusion to draw is that someone fixed the universe’s code or upgraded our cosmic server or something.”
“Really? You’re saying that this was evidence we were in a simulation this whole time and all these smart physicists knew the truth but they just didn’t want to tell us?”
“They just didn’t want to follow the evidence through to its logical conclusion. We had always just accepted that double-slit interference happened even though we didn’t understand why it happened. Let’s assume for a moment we’re in a simulation. What do details in the distance look like when you play video games?”
“Everything is fuzzy until we get close. So?”
“Simulations only render details if they are relevant. Analogously, which path a particle took was only determined when there was a reason to do so. It’s such a small thing, but it would be a waste of processing power to constantly calculate every irrelevant detail like that. If there are too many things to render then programs glitch or lag. Dr. Danet mentioned some experiment where the double-slit interference disappeared if they waited long enough between sending out particles. Our galactic program was happy to calculate the path of a single particle in a system over a short period, but any more complexity and it became simpler to apply probabilities to the system as a whole, hence the interference.”
“But if we are in a simulation, wouldn’t the computers and programs be way better than what we have so that they could account for all these little things and process them properly?”
“Maybe, but that doesn’t mean they would work very differently than the computers we have or that they have enough processing power to handle it all. It still stands that being in a simulation can make sense of why double-slit experiments give different results when we’re watching. If we checked which path a particle took, the software needed to render it, the waves collapsed, and the interference disappeared. If we didn’t ask, it didn’t bother to figure it out. It also explains those experiments where people saw interference even though a particle could physically take only one path but we just didn’t know which one it actually took. The simulation doesn’t bother figuring out which path since we can’t see it. And the pièce de résistance: gravity.”
“Gravity? How does gravity prove we’re in a simulation?”
“External objects should be exerting gravitational forces on the particles and vice versa. Why wasn’t gravity making the waves collapse? Shouldn’t its effects mean that external objects are interacting with the system and ‘observing’ it?”
“But the effects of gravity would be negligible. Photons barely have any mass or gravitational field.”
“I don’t care how small they are, gravity should have done something to the system. The simulation just didn’t account for it for whatever reason.”
“But maybe gravity doesn’t matter in these experiments, you don’t know. I’m still not convinced we’re in a simulation.”
“But nothing else has changed since yesterday. How could it be that just this one thing is different? You don’t think that’s weird? Literally it seems to be the only thing that our observations have affected. The universe could take or leave double-slit interference and now it’s decided to leave it. My guess is that it should have never been there in the first place.”
“I still don’t agree with you.”
“It’s hard to accept, but it’s the only explanation. Other than the God argument you gave earlier, but it would be so weird for God to change just this one little thing. Not to mention all the other issues with making an argument assuming God exists and dabbles in the details of quantum physics from time to time.”
She paused. I knew I had gotten through and she saw my reasoning.
“Wouldn’t it be awful to only be a piece of code though? I mean, let’s say you’re right, what’s the point of living if I’m just some random NPC doing a pretty good job in some stupid alien simulation? I don’t want to believe that.”
“Wishful thinking isn’t going to change reality. Besides, I think the opposite. Being a part of a program implies a purpose in ways that a random universe which exists by a cosmic accident does not.”
“But then you’re not really you, you’re just a bunch of lines of code that is mediocre at best. And wouldn’t that mean your algorithms are just making you believe this and say what you’re saying?”
“Maybe, but I don’t think it matters, since I’m still only whatever I can be. Knowing that I’m just some code on a computer is at least knowing what I am and that someone somewhere may really have a purpose for me. It’s weird, but I no longer feel any existential anxiety. All it took to calm me was the soothing sounds of quantum waves crashing.”
Noah Levin is a philosophy professor by day (and sometimes night) and science fiction author by night (and sometimes day). He received his PhD in Applied Philosophy from Bowling Green State University (USA) and has been published in academic journals in philosophy, popular philosophy anthologies, and edits a collection of free open textbooks in philosophy.
This piece examines some of the oddities in quantum physics, specifically the results of double-slit experiments, and speculates that they could be evidence for the simulation argument. I have my PhD in philosophy and some formal training in physics (including quantum physics and general and special relativity) and the weirdness of the double-slit experiment continues to baffle me. Specifically, I always wondered “why is it like this?” and after reading up on a ton of freaky experiments involving them over the past 10-20 years, came to the conclusion that not only was there no reason for double-slit interference to happen, it was so unique that if it ceased to occur, nothing else in the universe would change. This story is my attempt to explain my own thoughts on it, as well somewhat make a new argument in favor of the simulation hypothesis. And for good measure, I threw in a little bit about why it doesn’t matter.