2785: Marble Run

Explain xkcd: It's 'cause you're dumb.
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Marble Run
I have so many plans. It would incorporate a Galton board, a Ranque-Hilsch marble vortex tube, and a compartment lined with pinball bouncers with a camera-and-servo Maxwell's Demon that separated the balls into fast and slow sides.
Title text: I have so many plans. It would incorporate a Galton board, a Ranque-Hilsch marble vortex tube, and a compartment lined with pinball bouncers with a camera-and-servo Maxwell's Demon that separated the balls into fast and slow sides.


A Rube Goldberg machine is a fancifully complex system (either real or imagined), which makes use of an overly elaborate chain of actions. The name comes from an American cartoonist who was one of several people who became famous for depicting convoluted and outlandish processes for accomplishing simple tasks.

There's a long history of people building actual contraptions along these lines. Such devices are almost never intended for practical purposes, but exist entirely for entertainment, and as an exercise in building complex and carefully planned systems. This has become particularly common in the internet age, as videos of particularly interesting examples can gain popularity online. The most common category of these systems is probably the marble run (also known as a rolling ball sculpture), in which the goal of the system is to move one or more balls or marbles from the beginning of the arrangement to the end in interesting ways. This contrasts to the domino run where motions are transferred by many intermediate pieces painstakingly arranged, although both aspects are commonly combined in such contrivances.

When Megan tries to show Cueball an example of such a video, he refuses, not because he lacks interest, but because of how he predicts it will impact him. Cueball (likely as a stand-in for Randall), has sufficiently strong interest in things like designing, building and engineering complexity that he's certain he will eventually adopt building such systems as a hobby, and that it will dominate his time and attention. Accordingly, he appears to be deliberately delaying his exposure to them so that he can continue to pursue other hobbies, with the assumption that he will eventually succumb to this one. Randall foresees the amount of time he might use if he first began trying to construct his ideas into a marble run.

Megan responds that he knows where he's going, but is taking "a really interesting and circuitous path" to get there. This draws a parallel between the type of systems he's avoiding and his approach to life more generally, which Cueball expands upon by suggesting he would do some of the things a marble typically would in a marble run.

The title text mentions specific ideas Cueball plans to incorporate into such a set-up.

A Galton board is a device that distributes falling balls into a normal distribution. Its design is similar to those used in pachinko-style games.

A Ranque-Hilsch vortex tube is a device for separating compressed gas into hot and cold streams. While such a device isn't directly applicable to marbles, one can imagine using the principle to separate a stream of marbles based on speed.

Pinball bouncers are properly supposed to be the Bumpers in Pinball machines. In Randall's marble run there will be a compartment where the walls are lined with these bumpers. Supposedly there will be many marbles on the floor of this segment of the run, which will hit these bumpers and get a kick so they will move fast and randomly around the compartment, which is where the Demon comes in.

Maxwell's Demon is a thought experiment by James Clerk Maxwell which would violate the Second Law of Thermodynamics. Maxwell proposed that, if a container of air was separated by a divider, with a door that allowed only one molecule through at a time, and a theoretical "demon" were to control the door to sort high-energy atoms into one side and low-energy atoms into the other, the two sides would develop a temperature difference with no energy input. While such a system wouldn't actually be possible without energy input, it remains a compelling thought experiment.

Randall's version of this apparently involves the marbles bouncing around inside the bouncer-lined compartment, with an automated system to divert the fastest moving marbles into one side, and the slowest moving into the other, presumably to output higher velocity balls into one subsequent part of the arrangement, and slower ones into another. As these are macroscopic scales this would not be impossible, just really difficult.

Knowing Randall and his fans, some might design something using his ideas from this comic.


[Megan is walking towards Cueball and showing her phone. Cueball holds a hand to his face and looks away.]
Megan: Check out this cool video of a Rube Goldberg marble run.
Cueball: No! Not yet.
[Megan has lowered her phone. Cueball has his hand in a fist.]
Cueball: I've always known I'm doomed to eventually become one of those people who builds elaborate marble runs in their garage.
Cueball: I can feel the pull.
Cueball: So satisfying.
[Close-up on Cueball.]
Cueball: I just want to do as many other things as I can before I give in and disappear into that world.
[Megan and Cueball are walking.]
Megan: So you know where you're going to end up, but you're trying to take a really interesting and circuitous path to get there.
Cueball: Exactly. Bounce around, maybe go off a few jumps.

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Sorry if this is a mess (it's my first time editing). ProgrammerG (talk) 22:02, 5 June 2023 (UTC)

It's honestly much better than anything I could have done. Trogdor147 (talk) 22:04, 5 June 2023 (UTC)
Hey, it's all good. Not sure what you wrote (as opposed to anyone else that then pounced upon it, before I first saw it), but we have our own Rube Goldbergesque way of bashing it all into a (largely) mutually-approved shape. I think I spot some further changes I'd like to make, so I'm going to dive back in in a moment, but it has to start somewhere!
...the only big picky thing I'd say (to whoever did this, here or elsewhere recently), is that its fairly standard to note use the [URL link text] format when you can use the hand {{w}}-template to write {{w|Wiki article title|link text}}, instead, and often this lets you miss the "|link text" part out because the Wiki article title is the link text you want. I mean someone who died whilst creating a template to make this more streamlined, ought to have their work put to good use... ;) 23:36, 5 June 2023 (UTC)

Added Citation-needed for pacincko inspiration. I mean, I think the order of appearance is even wrong for that to be possible.RandalSchwartz (talk) 00:04, 7 June 2023 (UTC)

Hold it. Is this an actual citation needed, or a sarcastic one? If it's a sarcastic one, keep it as is, but I don't think it is. If it is an actual one, then use this tag.[actual citation needed] Trogdor147 (talk) 02:58, 7 June 2023 (UTC)
I read it as an ACN instance (thought as much myself, but hadn't then done basic checks), and the above statement reinforces the feeling.
  • Use {{Citation needed}} for "this is so obvious, it'd be funny to say it isn't" situations. And sparingly! ...like, you don't even need one in every single article, never mind several in a single paragraph, because it then just becomes a "who can put a CN in every article/paragraph first" competition, rather than a considered bit of humour (which others might consider is better elsewhere/not there because of their own ideas about that, of course). There are exceptions where maybe over-use is the point (self-referentially in the Wikipedian Protestor article, arguaby), and long and complicated comic descriptions might have many opportunities across a large number of sub-sections for which choice CNing can pop up in a wide sample of their mini-explanations. Although you will find that it's perfectly possible to go too far and thus a later editor decides that none of them deserve to remain, even the genuinely well placed one(s).
  • Use {{Actual citation needed}} for genuine 'proper' use of tag, as per elsewhere. Again, sparingly. If you know it's a wrong fact, best to factualise it (or contextualise it, where there's vital nuance that you're aware of) whenever you can. "Begging the question" (an ambiguous phrase, but either use of it) should be considered a stop-gap. Perhaps you intend to return and phrase your doubts properly when you have confirmed your objections/suspicions (or, otherwise, can remove it).
And also put it after the punctuation. e.g. following any comma,{{like here}} and not displacing the punctuation{{like here}}. (Although it can be tricky for some cases.{{here is fine}} But it probably needs a rewrite, anyway, if you're left with a tricky question of placement.{{like here?}}){{or here?}} ...but if you're not trying to shoehorn the tags in, beyond reasonable use, if you can't decided how it looks best then perhaps that means that it also has no point being there, which just reinforces my earlier suggestion on constraint.
YMMV, but then (OtherPeople's)MMV too. So things tend to settle down to the compromise consensus where it just works nicely enough for everyone. 09:58, 7 June 2023 (UTC)

I don't know why, but I feel like the phrase "maybe go off a few jumps" has been used by Randall (or somewhere) before, but I can't find anywhere except here/in the original cartoon and it's bugging me that it seems so familiar but there's no evidence of it in the 30-ish seconds of searching I've done so far. 16:35, 7 June 2023 (UTC)