---
title: "Simulations within simulations · How deep can a stack of simulations go? · Simulation Hypothesis"
url: https://simulation-hypothesis.com/nesting
description: "Build a stack of worlds, each running the next. A simulated computer can never out-compute the world it runs in, so every layer has less than the one above."
license: https://creativecommons.org/licenses/by/4.0/
credit: "Ross Allan Dahl, Simulation Hypothesis (simulation-hypothesis.com)"
---

# Simulations within simulations · where the stack stops

Everything a simulated computer does is computed by the machine running its world. So a nested simulation can use at most a share of its parent’s computing, and never more than its world’s matter could compute at Lloyd’s bound. Every layer has less computing than the world that runs it.

If the parent world is resolved atom by atom, nesting adds nothing to the base reality’s total. A computer built inside it is ordinary matter, and that’s already counted. If the parent is coarser, nothing inside it can compute. Then the operator has to run the inner simulation separately, on its own computing. Other dials stay at the [Sandbox](https://simulation-hypothesis.com/sandbox) baseline.

## The share each world uses

Share of a world’s computing used to run the simulation inside it: **1%** wild guess 

At 100%, a world does nothing but run the next one down. Our own civilisation uses a tiny fraction of its matter for computing.

## The stack

1. Base reality Physics like ours: 1% of every kilogram in the observable universe at Lloyd’s bound, 8.1 × 10^101 FLOPS.
2. Layer 1 One brainOne roomEarthSolar systemMilky WayObservable universePainted setOrganTissueCellOrganelleProteinMoleculeAtomParticleQuarkQuantum, mean fieldQuantum, fully entangled needs 1.3 × 10^68 FLOPS; the base reality allows 8.1 × 10^101 FLOPS. **Runs.**
3. Layer 2 One brainOne roomEarthSolar systemMilky WayObservable universePainted setOrganTissueCellOrganelleProteinMoleculeAtomParticleQuarkQuantum, mean fieldQuantum, fully entangled needs 6.0 × 10^41 FLOPS; its parent allows 1.3 × 10^66 FLOPS (its share of the parent’s computing). **Runs.**
4. Layer 3 One brainOne roomEarthSolar systemMilky WayObservable universePainted setOrganTissueCellOrganelleProteinMoleculeAtomParticleQuarkQuantum, mean fieldQuantum, fully entangled needs 10^21 FLOPS; the base reality allows 8.1 × 10^101 FLOPS. **Runs.**  Its parent is coarser than atoms and can’t contain a computer, so the base reality runs this layer directly.

Add a layer Remove the last 

## What the base reality runs

The stack runs **3 layers** deep. The base reality has to supply **1.3 × 10^68 FLOPS**, for 2 layers computed separately.

A layer resolved at atom detail or finer can contain working computers. These numbers come from the Sandbox engine, with everyone alive computed as a functional mind and time running from 1900\. The share is a wild guess. The ceilings are textbook physics.