“In 1999, the idea went big at the movies: The Matrix.”
All episodes
Episode
Are We Living in a Simulation?
Are we living in a simulation? Elon Musk thinks it's almost certain. The physicist Sabine Hossenfelder says the idea isn't science at all. We take a close look at Nick Bostrom's famous argument, ask who would be running a simulation like that, and what physics can actually measure. Plus two widely reported papers from 2025 that have since been challenged. Is the whole thing just the fashion of our time, like the sun god's boat or clockwork once were? And we end up with the question of why the world in your head looks sharp everywhere.
Sources
50 claims, 79 sources. Research as of October 18, 2026.
How we check
This page lists every factual claim from the video, with the sources it rests on. Every claim in the video is backed by these sources. We saved each page when we read it. The archived copies on the Internet Archive show what the page said at that time, even if it changes later.
Not everything is equally well backed. We say so openly in the video, and here it's marked on every claim:
- Confirmed
- At least two independent, reputable sources say the same thing.
Found a mistake? Tell us in the comments under the video or at hi@kadeemy.com. We pin corrections to the top there.
Intro 0:00A green blob
0:31 Confirmed
“The hero has to choose. With the red pill, he learns the truth. With the blue one, everything stays the way it is.”
0:45 Confirmed
“Some people take this simulation idea pretty seriously.”
“The entrepreneur Elon Musk thinks it's almost certain that we live in a simulation.”
Confirmed
“Plus two widely reported papers from 2025 that have since been challenged.” (video description)
Chapter 1 1:22Three possibilities
1:26 Confirmed
“In 2003, the philosopher Nick Bostrom of the University of Oxford published a paper with an unusual question in its title: Are You Living in a Computer Simulation?”
1:48 Confirmed
“Bostrom makes a rough estimate: a computer with the mass of a planet could simulate the entire mental history of humankind. Using less than one millionth of its power, in a single second.”
“Then there would be far more simulated minds than real ones. And if you don't know which one you are, you should bet on being one of the many.”
2:30 Confirmed
“And in 2018, the astrophysicist Neil deGrasse Tyson put the odds of a simulation at better than fifty-fifty.”
2:39 Confirmed also at 2:46, 2:52, 2:58
“Bostrom himself doesn't go that far. His argument is an either-or. At least one of three possibilities is true.”
3:07 Confirmed
“Bostrom himself wrote that, as long as we know so little, it's reasonable to spread our confidence roughly evenly across all three.”
3:15 Confirmed also at 3:29, 3:33
“In 2020, the astronomer David Kipping ran the numbers. He starts by giving both cases, real or simulated, the same chance, like a coin toss. The result: just under fifty percent for the simulation.”
3:46 Confirmed
“The argument assumes that a computer can produce consciousness at all. Whether that's possible, nobody knows.”
Chapter 2 3:52Who's running it?
“In Bostrom's argument, the answer is surprisingly close to home: our own descendants. He calls them ancestor simulations.”
4:21 Confirmed also at 4:27, 4:33
“Bostrom writes that the operators would, in some ways, be like gods to the simulated.”
5:02 Confirmed
“It could be sitting inside a simulation itself, and so could its operators. Reality would then have many levels, Bostrom writes.”
Context: Addition (as of 2026-10-06): David Wolpert (Santa Fe Institute) shows in a formal framework (Journal of Physics: Complexity, Dec. 2025) that deeper levels do not necessarily have to lose computing power and that infinite chains of simulations are possible without contradiction; a world that can simulate ours could, under certain assumptions, itself be reproduced in ours (S70). The paper provides no experiments or predictions. (adversarial review 2026-10-06 A03)
5:15 Confirmed
“The argument depends on the wishes of beings we know nothing about. Maybe they ban simulations like this. Maybe they just find them boring.”
Chapter 3 5:35Can we test it?
5:39 Confirmed
“For physicists, simulations are everyday work. Some compute the inside of atomic nuclei on supercomputers, on a grid of points in space.”
5:48 Confirmed
“In 2012, a group led by the physicist Silas Beane turned the tables. If our universe itself were computed on a grid like that, you should be able to detect the grid somewhere.”
“If space had a grid, the most energetic particles wouldn't arrive equally often from every direction.”
Context: An upper limit alone would not point to a lattice: in the spectrum of cosmic rays a cutoff has long been measured (GZK limit) and explained without a lattice, by the interaction of the particles with the cosmic microwave background (S07). Beane and colleagues use exactly this measured cutoff to put an upper bound on the lattice spacing (F19, S05). The actual telltale sign of a lattice would be the directional pattern of the most energetic particles. The picture sticks with the bar "upper limit"; an extra label would have overloaded the scene in its 18 seconds (adversarial review 2026-10-06 A04).
6:14 Confirmed
“From the measured energies of the rays, they concluded: if there is a grid like that, it's unimaginably fine.”
6:25 Confirmed
“Physicists know of a tiny length, the Planck length. Written out in meters, there are thirty-four zeros after the decimal point before the first digit.”
6:35 Confirmed
“But it's not necessarily the smallest pixel in the world. At that size, our theories break down. Whether space really falls apart into grains there, nobody knows.”
6:47 Confirmed
“At Fermilab, near Chicago, a team built two laser instruments with arms about forty meters long, roughly a hundred and thirty feet. They were looking for a faint jitter that grainy space might give away. In 2015 they reported: for this idea, they found no trace.”
- Holometer rules out first theory of space-time correlations
- Holometer FAQ
- First measurements of high frequency cross-spectra from a pair of large Michelson interferometers (Holometer, arXiv 1512.01216)
- Fermilab Experiment Finds No Evidence That We Live in a Hologram
- Fermi National Accelerator Laboratory
- Directions to Fermilab
7:11 Confirmed also at 0:53, 7:07
“People who believe in the simulation don't explain how a program is supposed to produce exactly the laws of nature that we measure.”
7:26 Confirmed also at 7:31, 7:34
“Online, a few people even claim they saw the source code of the world while on psychedelics.”
7:39 Confirmed also at 8:33, 13:00
“Science can only test specific designs, like the grid. Not the simulation as a whole.”
7:50 Confirmed
“In 2025, two papers made headlines.”
- Astrophysical constraints on the simulation hypothesis for this Universe: why it is (nearly) impossible that we live in a simulation
- Consequences of Undecidability in Physics on the Theory of Everything
- Your reality really could be a simulation, say experts. Here's why
- Physicists Just Ruled Out The Universe Being a Simulation
7:53 Confirmed
“A team led by the physicist Mir Faizal argues, using mathematics, that a complete description of the world needs more than any program can work out step by step. So, they conclude, the universe can't be a simulation.”
Context: As of 2026-10-06: Evan Redden objects in a comment (arXiv, Nov. 2025, not peer reviewed): undecidability limits what can be proven, not what can be executed; without evidence of hypercomputation in nature, the conclusion that a simulation is impossible is not justified (S68). A letter in the same journal (Weicheng Cui, JHAP, spring 2026), on the other hand, explicitly agrees with Faizal and colleagues, including on the conclusion about the simulation, and only disputes their claim to a complete theory (S69). The debate is open, as the episode says (adversarial review 2026-10-06 A03).
- Consequences of Undecidability in Physics on the Theory of Everything
- Physicists Just Ruled Out The Universe Being a Simulation
- Your reality really could be a simulation, say experts. Here's why
- Evan Redden, Provability vs. Execution: A Comment on "Consequences of Undecidability in Physics on the Theory of Everything" (arXiv 2512.11807, Nov. 2025)
- Weicheng Cui, Discussion on Consequences of Undecidability in Physics on the Theory of Everything (Letter, JHAP 6/2, spring 2026)
8:07 Confirmed
“And the astrophysicist Franco Vazza runs the numbers: recomputing our universe down to the last detail would take more energy than there is in the observable universe.”
Context: As of 2026-10-06: A published comment on Vazza (Eliott Edge, Chad Ashton Brown, Frontiers in Physics, April 21, 2026) counters that Bostrom's argument does not require computing the whole universe continuously, only experienced reality without noticeable errors (S63). That is the argument the episode itself makes (F41). (adversarial review 2026-10-06 A03)
8:20 Confirmed
“But both depend on assumptions about how a simulator would have to compute.”
8:25 Confirmed
“Bostrom already wrote back then that it's enough to compute just precisely enough that the simulated people don't notice anything.”
Chapter 4 8:38Just the fashion of our time?
“… the physicist James Gates found patterns in the equations of supersymmetry, a still unconfirmed theory of particles, that resemble the error-correcting codes computers use.”
9:11 Confirmed
“Neil deGrasse Tyson, who moderated a 2016 debate on the question, asked him: if we're in an I.T. revolution and finding I.T. solutions to our problems, maybe it's just the fad of the moment? If you're a hammer, every problem looks like a nail.”
“For the ancient Egyptians, the sun god Ra rode across the sky in a boat every day. At night he traveled through the underworld, and in the morning he came back out.”
9:55 Confirmed
“Then the world became clockwork, for Kepler …”
9:58 Confirmed
“… and for Boyle.”
9:59 Confirmed
“Nerves became pipes, like the ones in fountains …”
10:02 Confirmed
“… then telegraph wires …”
10:04 Confirmed
“… and the brain became a telephone switchboard.”
10:11 Confirmed
“For the world and for the mind alike, every era reaches for whatever impresses it most.”
10:23 Confirmed
“More than two thousand years ago, the Chinese philosopher Zhuangzi told of a dream in which he was a butterfly. When he woke up, he no longer knew: Was he Zhuangzi, who had dreamed of being a butterfly? Or a butterfly, dreaming of being Zhuangzi?”
10:39 Confirmed
“Plato described people who spend their whole lives sitting in a cave, seeing only shadows on the wall. They take the shadows for reality.”
10:48 Confirmed
“And in 1641, René Descartes asked whether an evil demon could be deceiving him about everything.”
“Maybe the simulation is simply our era's picture for a very old question: Is any of this real?”
Chapter 5 11:18So what?
11:40 Confirmed
“In his 2022 book Reality Plus, he argues that even a simulated world would be a real world. The table would just be a digital table. But it would be there.”
Chapter 6 11:52Sharp where you look
12:08 Confirmed also at 12:01, 12:17
“But in physics, observing doesn't mean a person with eyes. It's enough for the particle to come into contact with its surroundings, say, a measuring device.”
12:31 Confirmed
“Your eye only sees sharply in a tiny spot, about the size of your thumbnail at arm's length. Around it, things get blurry fast.”
12:40 Confirmed
“And yet the world looks sharp everywhere, because your brain stitches the picture together.”
12:46 Confirmed
“The neuroscientist Anil Seth even calls perception a controlled hallucination. Your brain is constantly building a model of the world and checking it against your senses.”