---
title: "Planetary Computation Unit"
description: "Bratton's yardstick for planetary computation taken as a whole: one PCU is the aggregate artificial computing capacity on Earth at a given moment, roughly one zettaFLOPS (ten to the twenty-first operations per second) in 2025."
type: "glossary-term"
canonical_url: "https://antikythera.wiki/terms/planetary-computation-unit"
md_url: "https://antikythera.wiki/md/terms/planetary-computation-unit"
last_updated: "2026-09-06"
site: "Antikythera Wiki"
---

# Planetary Computation Unit

> A working definition written for this wiki from the reading notes; not Antikythera's own wording. From Antikythera Wiki (https://antikythera.wiki/terms/planetary-computation-unit), an independent guide to Antikythera's published work.

Bratton's yardstick for planetary computation taken as a whole: one PCU is the aggregate artificial computing capacity on Earth at a given moment, roughly one zettaFLOPS (ten to the twenty-first operations per second) in 2025. Introduced in entry 9 of Accept All Cookies, restated in The Noocene as a "Planetary Computing Unit", and used in the Diffusion announcement to set a design horizon: with capacity doubling about every thirty months, 10 PCU arrives within a decade and 100 PCU within two, a world Bratton says will be as unfamiliar as today is to our grandparents. The unit turns Planetary Computation from a description into a quantity. A pointed precedent is The Stack, where a zettaflop climate simulator was a hypothetical the size of Paris whose energy use would be the largest climatic event it modelled; a decade later that figure is the baseline. No text shows how it was estimated.

## Appears in

- [The Noocene](https://antikythera.wiki/work/journal/noocene) (2025-11-21)
- [Diffusion: A New Venture for Antikythera](https://antikythera.wiki/work/substack/2025-09-25-diffusion-a-new-venture-for-antikythera) (2025-09-25)
- [Accept All Cookies](https://antikythera.wiki/work/book/accept-all-cookies) (2025-05-10)
- [The Stack](https://antikythera.wiki/work/book/the-stack) (2016-02-19)

_Glossary generated 2026-09-06._