A Bunch of Rocks
A bunch of rocks
Number 505
Date Nov. 17th 2008
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A Bunch of Rocks is the 505th xkcd comic.


German computer scientist Konrad Zuse theorized that that the entire universe is the output of a deterministic computation on a single cellular automaton. In other words, the universe is actually the representation of a computer simulation.

So in this comic, the main character has created an entire universe using a simple computer -- in this case, an elementary cellular automaton.

The comic also touches on the idea of Turing-completeness and the assumptions around Turing computers needing infinite time and space to complete calculations.

Going by the images, the specific cellular automaton used here was Rule 110. Steven Wolfram proposed that there are 256 elementary cellular automata , each of which is categorized as a different "rule." This ties into the mouseover joke, which reference Wolfram's Rule 34 (one of the 256 elementary automata) with the Rule 34 of the internet. The latter posits that there exists porn of any conceivable topic... in this case, up to and including a rule about elementary computers.

Mouseover textEdit

"I call Rule 34 on Wolfram's Rule 34."

See alsoEdit

Wikipedia: Turing-completeness

Wikipedia: Rule 110

Wikipedia: Elementary cellular automata

Rule 34 in XKCD:

The world as a computer simulation:

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