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The simulation hypothesis
2003· Idea
PhilosophyAn argument about reality that science can't test (yet).
The philosophical idea that our universe could be a computer simulation run by some more advanced civilization.
See it on the Science map →How it works
Philosopher Nick Bostrom framed it in 2003 as a three-way choice: almost no civilizations reach the ability to run detailed simulations of minds; or those that can almost never do it; or we are very probably simulated, since simulated minds would vastly outnumber real ones. One of the three must hold, he argued. Popular versions cite pixel-like limits at the Planck scale or holography, but these are analogies, not evidence.
Why it matters
It is a serious thought experiment about probability, consciousness and computing. It is philosophy, not physics: no observation currently favors or rules it out.
How we know
None so far. In 2012 physicists Beane, Davoudi and Savage proposed that a grid-based simulation might leave signatures in high-energy cosmic rays; no such signs have been found.
Still a mystery
Whether consciousness can run on a computer, whether simulating a universe is even possible, and whether the idea can ever be tested are all open.
Connections (8)
▸Quantum computing shows physics can be computed, fueling The simulation hypothesisPhilosophy
The relationship
Quantum computers exist because nature can be imitated by computation: a machine made of quantum parts can model other quantum systems. If every physical process can in principle be simulated, then a whole universe might be too. Simulation fans take this as a reason the idea is not absurd, though it says nothing about whether ours is simulated.
How the link was found
Richard Feynman proposed quantum computers to simulate physics in 1981. David Deutsch argued in 1985 that a universal quantum computer could simulate any physical process.
Is it proven?
Quantum computers have simulated small molecules and materials, and Google's 2019 machine beat classical computers on one narrow task. That supports "physics is computable" in small cases, not that we live in a simulation.
Open questions and mysteries
Simulating a universe in full detail may require a computer at least as large as the universe itself. Whether shortcuts exist is unknown.
▸The holographic principle inspires talk of The simulation hypothesisPhilosophy
The relationship
The holographic principle says a 3D world could be fully encoded as data on a 2D surface. Popular accounts read that as "our world is a projection," which sounds like a rendered simulation. The resemblance is loose: holography is about how much information space can hold, and says nothing about a computer or a programmer.
How the link was found
Science writers and commentators made the link, especially after the 2000s. Physicists who developed holography have generally not endorsed it.
Is it proven?
No evidence connects them. Fermilab's Holometer (2014-15) searched for a predicted holographic "jitter" in space and found none, ruling out that specific model.
Open questions and mysteries
Whether information-based physics changes the philosophical odds of a simulation is debated, but not testable now.
▸"It from bit" is a close cousin of The simulation hypothesisPhilosophy
The relationship
Both ideas put information at the bottom of reality. "It from bit" says the world is built from yes/no answers. The simulation hypothesis adds a computer running the code and someone who built it. Take Wheeler's idea and add a programmer, and you are close to the simulation picture.
How the link was found
Wheeler (1989) and Bostrom (2003) developed them separately; later writers, including Bostrom's commentators, drew the comparison.
Is it proven?
Neither idea is tested, and both are philosophy. Their similarity is conceptual, not demonstrated.
Open questions and mysteries
If reality is information, does it need a computer at all? Wheeler thought not; simulation fans think so.
▸Nick Bostrom formulated the argument behind The simulation hypothesisPhilosophy
The relationship
Bostrom built a careful probability argument. If advanced civilizations can and do run many detailed simulations of minds, simulated minds would far outnumber real ones, so a typical mind like ours is probably simulated. He did not claim we are simulated, only that one of three options must hold.
How the link was found
Nick Bostrom, "Are You Living in a Computer Simulation?", Philosophical Quarterly, 2003.
Is it proven?
It is a logical argument, not evidence. It rests on assumptions, such as that consciousness can run on computers, that critics dispute.
Open questions and mysteries
Which of his three options is true, and whether the reasoning about "typical observers" is valid, are unsettled.
▸Elon Musk: "one in billions" popularized The simulation hypothesisPhilosophy
The relationship
Musk retold the argument with a video-game twist, saying games went from Pong to realism in about 40 years and will become indistinguishable from reality. With billions of such worlds and one base reality, he argued we are likely simulated. His fame pushed the idea into mainstream conversation.
How the link was found
Elon Musk, Code Conference, June 2016, in response to an audience question.
Is it proven?
No proof. It assumes continued progress and that simulations would be run and contain conscious minds. It is an opinion, not a scientific result.
Open questions and mysteries
Whether better graphics have anything to do with simulating minds and physics is doubtful.
▸The simulation hypothesis reads the grain of space as "pixels" at The Planck scale: the smallest meaningful sizePhilosophy
The relationship
The Planck length, about 10^-35 meters, is where our theories stop working. Simulation fans compare it to pixel size: a grid below which nothing finer exists. Physics does not say space is a grid there; it only says current theories break down. The pixel picture is an analogy, not a finding.
How the link was found
Popular writers made the comparison. In 2012 physicists Silas Beane, Zohreh Davoudi and Martin Savage asked what a grid-based universe would leave in cosmic rays.
Is it proven?
No pixel effects have been found. Gamma-ray burst observations, such as GRB 090510 in 2009, show light of different energies travels together, ruling out simple grids near the Planck scale.
Open questions and mysteries
Whether space has any grain at the Planck scale is unknown; quantum gravity has not settled it.
▸The mathematical universe hypothesis is a computer-free cousin of The simulation hypothesisPhilosophy
The relationship
Both say reality is fundamentally abstract structure. The simulation hypothesis needs a computer and an outside world to run it. Tegmark's view drops that: the universe is a mathematical structure, existing without being computed. Tegmark has argued that a computer adds nothing, since the math exists either way.
How the link was found
Max Tegmark, in his 2007 paper and 2014 book, discussed simulations and argued his view makes them unnecessary.
Is it proven?
Neither is tested; both are philosophy. The relationship is a matter of argument, not evidence.
Open questions and mysteries
If the universe is just math, why does it feel like it is happening, with time passing? Neither idea explains experience.
▸Observers and consciousness is central to The simulation hypothesisPhilosophy
The relationship
Bostrom's argument counts observers: if simulated minds vastly outnumber biological ones, a typical observer is simulated. That only works if a simulation can contain genuine conscious observers. So the whole hypothesis hinges on what consciousness is and whether it can run on a computer.
How the link was found
Nick Bostrom (2003) made the assumption explicit, calling it substrate independence: the idea that minds depend on information processing, not on biology.
Is it proven?
Not proven. Science has no accepted explanation of consciousness, so whether simulated minds would be conscious cannot be tested now.
Open questions and mysteries
If consciousness requires biology or something non-computable, as some philosophers argue, the simulation argument fails.