505: A Bunch of Rocks

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search
A Bunch of Rocks
I call Rule 34 on Wolfram's Rule 34.
Title text: I call Rule 34 on Wolfram's Rule 34.

[edit] Explanation

Ambox notice.png This explanation may be incomplete or incorrect: What is the diagram to the right of the Epitaph of Stevinus? Nobody counts the panels, what is "panel 13"? Too may parentheses here, many items are not well explained. Language is still a major issue. This is a candidate for the "Incomplete explanation of the day."
If you can address this issue, please edit the page! Thanks.
Cueball awakens to find himself trapped for eternity in an endless expanse of sand and rocks. At first, he uses this time to derive all of mathematics and physics, including quantum mechanics and general relativity. The Swiss patent office line refers to Albert Einstein, who supposedly came up with the idea for general relativity while mundanely employed as a Swiss patent clerk.

Next, armed with infinite time and space (and rocks), Cueball uses the rocks to build a cellular automaton, a computational model based on simple rules to advance from one state to the next. Certain cellular automata are Turing-complete, which means that they can be used to represent any computer program (given finite-but-possibly-extremely-large time and space). He specifically seems to be running Wolfram's Rule 110, which is indeed capable of universal computation. Cueball then uses his enormous, hand-powered computer to simulate a universe.

When using Rule 110 for universal computation, one builds a background pattern, which can be seen in the comic (especially panels 12 and 20) as the nigh-universal pattern of smaller triangles, and then performs computation by sending out "rockets" (the patterns of larger triangles seen in panel 20) to collide and interact with each other (for example, the triangular outlines in panel 13).

The last panel then implies that the universe Cueball is simulating is, in fact, our universe. In panel 24, Cueball mentions he must have made a mistake in the last "billions of billions of millenia." A millennium is a thousand years, which implies that the time needed to run this computer through a single step of computation is trillions of years. This means he spends much more time on a single step of computation than our universe has spent existing, and this single step of computation simulates an extremely short span of time (a Planck time most probably); to put this massive difference into perspective, our universe is around 13.772 billion years old, which corresponds to roughly 8,060,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 years of Cueball's computation. (Give or take a few duodecillion years.) Suffice to say, this is a very long time.

The diagrams in panel 8 are, from left to right: A Gaussian function (probably the Normal distribution); the Epitaph of Stevinus; a weird diagram with lines in it (something to do with thermodynamic cycles?).

Rule 34 is a humorous rule of the Internet which states "If you can imagine it, there is porn of it. No exceptions." Wolfram's Rule 34 is a cellular automaton. Randall is suggesting that someone should make pornography featuring the cellular automaton in question. This might prove to be quite challenging, as Wolfram's Rule 34 quickly devolves into a bunch of diagonal lines given almost any input.

[edit] Transcript

[Cueball is walking alone in a desert, narrating his own situation.]
So I'm stuck in this desert for eternity.
I don't know why. I just woke up here one day.
I never feel hungry or thirsty.
I just walk.
Sand and rocks
stretch to infinity.
As best as I can tell.
[Cueball is sitting in the desert, in a contemplative position.]
There's plenty of time for thinking out here.
An eternity really.
[Cueball is sketching stuff in the sand.]
I've rederived modern math in the sand
and then some.
[Different graph types are depicted.]
Physics too. I worked out the kinks in quantum mechanics and relativity.
Took a lot of thinking, but this place has fewer distractions than a Swiss patent office.
[Cueball is walking along the desert, laying out rocks.]
One day I started laying down rows of rocks.
[Cueball continues to deploy rocks.]
Each new row followed from the last in a simple pattern.
[Image continues to zoom out showing laid out rocks.]
With the right set of rules and enough space,
I was able to build a computer.
Each new row of stones is the next iteration of the computation.
Sure it's rocks instead of electricity, but it's the same* thing.
Just slower.
*Turing-complete
[Cueball in contemplative pose.]
After a while, I programmed it to be a physics simulator.
[A particle labeled by binary strings.]
Every piece of information about a particle was encoded as a string of bits written in the stones.
[A Feynman diagram showing two particles interacting.]
With enough time and space, I could fully simulate two particles interacting.
[Cueball standing before the vastness of the desert.]
But I have infinite time and space.
[Depiction of various galaxies and other systems.]
So I decided to simulate a universe.
[Cueball is walking about his rocks, moving them around.]
The eons blur past as I walk down a single row.
[Zoom out of the rows of rocks.]
The rows blur past to compute a single step.
[Shows placement of two particles.]
And in the simulation...
[The two particles have moved; an after-image of their previous placement is present.]
...another instant ticks by.
[A person observes a mote of dust vanish.]
So if you see a mote of dust vanish from your vision in a little flash or something
[Cueball is holding two rocks, rearranging them.]
I'm sorry. I must have misplaced a rock
sometime in the last few billions and billions of millennia.
[Cueball in front of the vastness of his infinite desert.]
Oh and...
[Cueball in a classroom setting with head in hands, girl and professor are present; there are apparently less than five minutes left in the class.]
If you think the minutes in your morning lecture are taking a long time to pass for you...
Comment.png add a comment!

Discussion

Weird thing with lines in it

probably has something to do with relativity -- two objects moving, arriving at different points at the same time, or maybe a diagram of spacetime. 66.202.132.250 16:44, 10 June 2013 (UTC)

It's a Feynman Diagram 206.174.12.203 19:24, 10 June 2013 (UTC) Toby Ovod-Everett

I did add the incomplete tag because this comic and also the explain is still really complex. More important: People without a proper physics background never will understand. --Dgbrt (talk) 21:01, 10 June 2013 (UTC)

There is a short story called "SOLE SOLUTION" by Eric Frank Russell which is quite similar to the one in the story. Just in case that matters. Maob (talk) (please sign your comments with ~~~~)

Re Rule 34 - the point is that this comic _is_ cellular automaton porn (as are the YouTube videos of Minecraft calculators and the like). Rule 34 works, bitches! 141.101.98.241 (talk) (please sign your comments with ~~~~)

Not sure what's incomplete about the explain. 0100011101100001011011010110010101011010011011110110111001100101 (talk page) 22:56, 11 February 2014 (UTC)

Yo calculus is the latin word for pebble! I learned this and had to come straight to this page! ahhh connections! 173.245.50.88 Sawyer Biddle

As it turns out, Rule 110 seems to be a really bad way to simulate a universe- you would be much better off using a Cyclic tag system, since Rule 110 takes dozens of generations and potentially hundreds of cells to simulate one step in such a system, or a more sophisticated cellular automaton, such as Wireworld. --Someone Else 37 (talk) 05:12, 9 March 2014 (UTC)
Personal tools
Namespaces

Variants
Actions
Navigation
Toolbox

It seems you are using noscript, which is stopping our project wonderful ads from working. Explain xkcd uses ads to pay for bandwidth, and we manually approve all our advertisers, and our ads are restricted to unobtrusive images and slow animated GIFs. If you found this site helpful, please consider whitelisting us.

Want to advertise with us, or donate to us with Paypal or Bitcoin?