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Ptolemy and Homer (Simpson)

Santiago Ginnobili · 379.9K views · 2008-07-11 · 3:50

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Overview

A short animation reconstructing a planet's looping orbit using Ptolemy's epicycles and deferents, with the epicycles tracing out the face of Homer Simpson. It shows how enough circles can reproduce nearly any shape.

On Hacker News

HN uses it as a vivid demonstration that Fourier series and epicycles can fit anything, and as a warning about models with too much wiggle room.

Recommended by 3 HN people across 3 months · HN mentions 2013–2022

Topics

Recreational & visual mathInformation theory & signal processingCosmology & astrophysics
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epicyclesfourier seriesptolemyoverfittingvisualization

What people said

jordigh · 2016-10 · Recommendation

I tl;dr'ed the article (sorry), but I wanted to say one thing about epicycles. They are not wrong and certainly can be used to explain motion, but the problem with them is that you can keep adding epicycles to fit any continuous orbit at all (this actually is because a Fourier series can converge to any continuous periodic function). This is my favourite visualisation of this fact: [VIDEO]

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JadeNB · 2015-10 · Recommendation

I'm only seeing an image, with no explanation, and it took me a while to realise what it was showing; so, in case anyone else is puzzled by it, each image is the sum of the previous one with a new factor (indicated by the "wheels upon wheels"). I think that the reconstruction of Homer Simpson's face (which I think I originally saw thanks to OP ColinWright!) may be a more convincing demonstration of the power of Fourier transforms: [VIDEO] . There's a Nautilus article about it, too: [LINK] (EDIT: and an HN post discussing that: [LINK] ).

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TheMakeA · 2013-11 · Recommendation

These guys are one of the reasons I love mathematics. Check this out too: [VIDEO] Edit: Didn't realize that this was also linked to in another thread on the front page as well.

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Sources

Video by Santiago Ginnobili, played through YouTube.

Data and selection notes

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HN Library: HackerTube export (2026-10-31) and open-index/hacker-news. Upstream summaries and classifications may contain AI errors.

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