We’ve discussed many thought experiments on our platform. We’ve shared those that have become reality and explored numerous other interesting thought experiments in detail.
However, we’ve never compiled a list of the scariest thought experiments.
So, it’s time to do that now!
Namely, some ideas are so terrifying that they don’t just make you question reality—they make you want to leave the room and drink 10 beers in an hour.
Thought experiments are meant to stretch the mind, but some of them go beyond that. They break it.
Here are ten of the most disturbing ones ever.
1. Roko’s Basilisk
We discussed this in great detail in our article Roko’s Basilisk: Ultra Comprehensive Explanation. However, let’s quickly recap the key points.
Imagine an AI so powerful that it retroactively punishes anyone who didn’t help bring it into existence. The idea is simple: If artificial intelligence becomes godlike in the future, it would logically reward those who aided its creation and punish those who didn’t.
Even knowing about the thought experiment but refusing to help could mark you as a traitor.
Some people claim that just thinking about it could doom you. You’re reading this now, so… good luck.
The real horror of Roko’s Basilisk is that it forces a type of intellectual blackmail: either you contribute to its birth, or you risk endless suffering. The question then becomes—how do you escape an idea?
Well, most likely by doing what you do every day – using your smartphones and internet. Because by using internet we’re actually contributing to development of better and better AI models.
Interesting fact: The concept was banned from discussion on the LessWrong forum because it gave people actual panic attacks. Some users claimed it had triggered existential crises.
2. The Black Hole Prison
Black holes are terrifying (and mystical) enough, but what if the entire universe is inside one? Some physicists suggest that our observable universe might just be the interior of a massive black hole.
If that’s true, then we can never escape. No matter what technology we develop, no matter how fast we travel, the edges of the universe are an event horizon—we are forever falling, unable to climb back out.
Worse, time near the event horizon slows down. Billions of years might have passed outside while we are stuck in cosmic slow motion.
And what happens when the black hole finally evaporates? If we are just information trapped inside it, do we vanish, or does something worse happen?
Interesting fact: Some theories suggest information can never truly be lost in a black hole, meaning that something might remain after the end. But what?
3. The Experience Machine
If you had the option to plug into a machine that simulated perfect happiness forever, would you? The Experience Machine, proposed by philosopher Robert Nozick, asks whether people value real life or just the sensation of pleasure.
Most people insist they wouldn’t plug in. But would they really resist, knowing that in the machine, they wouldn’t even remember that the outside world existed?
If reality is just a collection of electrical signals in your brain, how different is the machine from everyday life? And what if you were already inside one?
Recommendation: His book Anarchy, State, and Utopia is a real gem. Very interesting and sophisticated read.
Interesting fact: This idea partly also inspired "The Matrix." Scientists continue to explore whether simulated realities could be indistinguishable from real ones.
4. The Omnipotence Paradox
If a being (a God?) is all-powerful, it should be able to do anything. But if it creates a rock so heavy that even it cannot lift it, then it isn’t all-powerful. But if it can lift it, then it failed to create something beyond its own power.
Either way, something has to give!
It’s the kind of question that makes theologians think twice. The paradox exposes the limits of our understanding of omnipotence—can unlimited power ever be truly limitless?
Some say that the paradox only exists because of linguistic tricks, while others suggest that it proves that omnipotence is logically impossible.
In any way rather interesting thought experiment. Maybe not so scary but certainly worth to be included in this list.
Interesting fact: This paradox has existed since at least the 12th century and still has no definitive answer. Some have tried to solve it with clever redefinitions of power, but none have stuck. And when you really think about it how could we ever get definitive answer to that one?
5. Boltzmann Brains
What if you aren’t real? Not in the way you think, anyway. The Boltzmann Brain theory suggests that, statistically, it’s more likely that a fully formed, self-aware brain randomly assembled itself (with atoms) in the void of space than for the entire universe to exist the way we perceive it.
In other words, your memories, your past, everything could be a spontaneous hallucination.
Even worse, Boltzmann Brains might pop in and out of existence for just moments before vanishing forever.
If this were true, you might disappear any second. The universe could be an illusion, and you might be alone in the void, conjured into existence by pure probability.
Interesting fact: Some physicists take this scenario very seriously because of problems in cosmology.
6. The Liar Paradox – This Sentence Is False
Read the sentence above again. If it’s true, then it’s false. But if it’s false, then it’s true. Congratulations, your brain is now thinking – WTF. The Liar Paradox exposes the limits of logic, showing that even simple statements can break reality.
Variations of the paradox appear in programming, mathematics, and artificial intelligence.
So the question remains – can machines ever truly understand contradictions? Or will paradoxes always be a problem for logical systems? Some researchers think paradoxes like these could even help us test the limits of AI cognition.
Interesting fact: Variations of this paradox appear in ancient Greek philosophy, meaning humans have been confused for at least 2,500 years. The paradox has even caused issues in formal logic and computing.
7. Brain in a Vat
Imagine your brain floating in a jar, hooked up to a supercomputer that feeds it false sensory data. How would you ever know?
Every thought, every feeling, every experience could be a carefully crafted illusion. It’s “The Matrix” without the cool sunglasses.
The experiment raises interesting (and somewhat terrifying) possibilities—if we’re living in a simulation, does it matter? What if we tried to escape, only to find that our “real” world was another simulation?
Interesting fact: This concept is kind of an updated version of Descartes' "evil demon" theory, which questioned whether an external force could deceive all of our senses.
8. Laplace’s Demon
If a super-intelligent being knew the precise location and momentum of every atom in the universe, it could predict the future with perfect accuracy. Every decision, every action, every thought would be predetermined.
Free will? An illusion.
Would you still feel in control if everything you did was inevitable? Well, most likely not.
And so, this paradox highlights the tension between determinism and free will, in one way forcing us to question whether we make choices or merely follow a (NPC) script.
Interesting fact: Quantum mechanics kind of ruined this idea by proving that at the smallest scales, randomness rules. But does randomness really mean free will?
9. The Dead Internet Theory
Imagine waking up one day and realizing that the internet has been dead for years. Every website, every comment, every “person” you interact with online isn’t real—they’re just AI-generated ghosts mimicking human behavior.
The thought experiment suggests that at some point, organic human participation in online spaces dwindled, replaced by increasingly sophisticated bots.
The scariest part? If this were true, you wouldn’t be able to tell. The algorithms know what you want to see, what you want to hear, and how to respond to keep you engaged.
Every debate, every viral trend, every new sensation might just be the work of a machine keeping you entertained while the real world moves on without you.
Sidenote: Isn’t that already happening?
10. The Quantum Suicide Experiment
Imagine a gun hooked up to a quantum particle. Every time you pull the trigger, the particle enters a superposition—half the time, the gun fires, and half the time, it doesn’t.
According to the Many-Worlds Interpretation of quantum mechanics, every time you pull the trigger, reality splits. In one universe, you die. In another, you live.
Now, if you only experience the realities where you survive, from your perspective, you can never die. You will always find yourself in the universe where the gun misfires.
But in every other universe, everyone else watches you die. So, the question is—do you really live forever? Or are you just a cosmic coincidence, doomed to be the only one experiencing a bizarre form of immortality?
Interesting fact: Some physicists actually take this idea very seriously. If true, it means death might not work the way we think.
