A Blog by Ugo Bardi

Collapses are the way the universe gets rid of the old to leave space for the new. It was noted for the first time by the Roman Philosopher Lucius Anneaus Seneca (4 BCE-65 CE) and it is called today the "Seneca Effect."

Monday, July 11, 2022

The Mystery of the Mousetrap: Of Chain Reactions and Complex Systems




The "mousetrap chain reaction" from Disney's 1957 movie "Our friend, the Atom." A fascinating experiment that brings a curious question: Why is the mousetrap the only thing you can buy at a hardware store that can create a chain reaction? Another mousetrap-related mystery is why, with so many experiments done, so far nobody had tried to make measurements to quantify the results? Eventually, two Italian researchers, Ilaria Perissi and Ugo Bardi re-examined this old experiment, showing how it can be seen as much more than a representation of a nuclear reaction, but a paradigm of the behavior of complex systems. 


Walt Disney's 1957 movie, "Our Friend the Atom," was an absolute masterpiece in terms of the dissemination of scientific knowledge. It was, of course, sponsored by the US government. It was supposed to promote their energy policy which, at the time, was based on the concept of "atoms for peace." So, the movie was propaganda but, at the same time, it is stunning to think that in the 1950s, the US government was making an effort to obtain an informed consent from its citizens, instead of just scaring them into submission! Things change, indeed. But we can still learn a lot from this old movie. 

So, "Our Friend, the Atom" is a romp through what was known about atomic physics at the time. The images are stunning, the explanations clear, and the story is fascinating with a mix of hard science and fantasy, such as the story of the genie and the fisherman. I went through my studies in chemistry having in mind the images from the movie. Still today, I tend to see in my mind protons as red, neutrons as white, and electrons as green, as they were shown in the book. 

One of the fascinating elements of the story was the chain reaction made with mousetraps. I was so impressed by that experiment that I always had in mind to redo it and, finally, last year, my colleague Ilaria Perissi agreed to give me a hand. Together, we built our wonderful, new, improved, mousetrap machine! We braved the risks of flying balls and we managed to make our experiments with only minor damage to our knuckles. And we were the first, it seems, to make quantitative measurements of this old experiment. 

I will tell you about our results below but, first, a bit of history. The idea of the mousetrap chain reaction was proposed for the first time in 1947 by Richard Sutton (1900-1966). He was a physicist working at Haverford College, in Pennsylvania: a maverick physics teacher who loved to create demonstrations of scientific phenomena. And, no doubt, the idea to use mousetraps to simulate a nuclear chain reaction was nothing less than a stroke of genius. Too bad that Sutton is not mentioned at all in Disney's movie. 
 
Here is how Sutton proposed the experiment: 



Sutton seems to have actually performed his demonstration in front of his students, although we have no pictures or records of it. We tried to use the same setup, but we found that the corks are too light to trigger the traps, and the reaction dies out immediately. It works only if the traps are not fixed to the table and are left free to fly around, Indeed, Sutton doesn't mention that he fixed the traps to the table. The "flying trap problem" plagues most of the experimental setups of this experiment. But if the chain reaction is generated by flying traps, it is not anymore a simulation of an atomic chain reaction. 

After that Sutton published his idea, performing the mousetrap experiment in public seems to have become fashionable.  You can find another illustration of the setup in the 1955 book by Margaret Hyde: "Atoms today and Tomorrow.


Note how the experiment has changed, probably because of the problems to make it work with corks. Now there are no corks, but a marble is used to trigger one trap, which is linked to other mousetraps by a "heavy thread." Maybe it works, but it is not what Sutton had proposed, and it is hard to present it as a simulation of anything. 

So, in 1956, the filmmakers at Disney were probably scratching their heads and thinking of how they could make the mousetrap experiment work. Eventually, they decided to use ping-pong balls and a large number of mousetraps. You can see the results in the movie: traps are flying all over. Same problem: this is not what the experiment was supposed to do. And there is a reason: also, in this case, we tried to use the same setup, and we found that ping pong balls are too light to cause traps to snap. If the traps are fixed to the table, the experiment just fizzles out after triggering one or two traps at most. 

Strangely, so few people noted the problem: an exception was the nuclear physicist Ivan Oelrich, but that was in 2010! Most of the mousetrap experiments you can find on the Web (and there are many) are of the "flying-traps" type. It is a problem with science for the public: it is often flashy and spectacular, and signifying nothing. 

We found only two experiments on the Web where the traps were fixed to the supporting plate, as they should have been. But, even in these two cases, no quantitative measurements were performed. Strange, but there is this curse with popular science to be often despised and, sometimes, carry a negative mark on a physicist's career. 

But never mind that. Your dream team, Ilaria and Ugo, engaged in making the experiment in the correct way, with fixed traps, and at the same time measuring the parameters of the experiment. Our trick was to use relatively heavy wooden balls that could nicely trigger the traps. We also enlarged the area of the metal triggers using cardboard disks. Then, we used commercial cell phone cameras to record the results. 


It took a lot of patience: it is not easy to load 50 traps with 100 wooden balls, avoiding that they start going off when you don't want them to go off. To say nothing about the gate snapping directly onto the experimenter's fingers. Painful, but not a cause of permanent damage. We did that in the name of science, and it worked! Of course, some reviewers were horrified by a paper that was not using expensive equipment and complicated and mysterious calculations. But, with patience, we succeeded in seeing it published in a serious scientific journal. 

Excuse me for being proud of our brainchild, but I truly found it elegant how we could fit our data with a simple mathematical model. And how the trap setup mirrors not only the chain reaction in a nuclear explosion, but also several other phenomena that flare up and then subside. For instance, the trap array may be seen as a mechanical simulator of the Hubbert curve, with the traps as oil wells and the balls as extracted oil. It can also simulate whaling, various cases of overexploitation of natural resources, the diffusion of memes in cyberspace, and more. Not bad for an object, the mousetrap, that had been developed with just one purpose: killing mice. 


We conclude our paper on "Systems" with the following paragraph: 
Mousetraps seem to be the only simple mechanical device that can be bought at a hardware store that can be used to create a chain reaction. We do not know why this phenomenon is so rare in hardware stores, but chain reactions are surely common in complex adaptive systems. We believe that the results we reported in this paper can be helpful to understanding such systems and, if nothing else, to illustrate how chain reactions can easily go out of control, not only in a critical mass of fissile uranium but also in similar dynamics occurring in the ecosystem that go under the name of “overshoot” and “overexploitation”.
Yes, really, why are mousetraps so exceptional? Who would have thought?
 
Here is the post that I published a few months ago on this subject. 

The Mousetrap Experiment: Modeling the Memesphere

 Reposted from "The Seneca Effect" Nov 22, 2021

 Ilaria Perissi with our mousetrap-based mechanical model of a fully connected network. You can find a detailed description of our experiment on ArXiv


You may have seen the "mousetrap experiment" performed as a way to demonstrate the mechanism of the chain reaction that takes place in nuclear explosions. One of its earliest versions appeared in the Walt Disney movie "Our Friend, the Atom" in 1957. 


We (myself and Ilaria Perissi) recently redid the experiment with 50 mousetraps and 100 wooden balls. And here it is.

But why bother redoing this old experiment (proposed for the first time in1947)? One reason was that nobody had ever tried a quantitative measurement. That is, measuring the number of triggered traps and flying balls as a function of time. So, we did exactly that. We used cell phone slow-motion cameras to measure the parameters of the experiment and we used a system dynamics model to fit the data. It worked beautifully. You can find a pre-print of the article that we are going to publish on ArXiv. As you can see in the figure, below, the experimental data and the model go reasonably well together. It is not a sophisticated experiment, but it is the first time that it was attempted.



But the main reason why we engaged in this experiment is that it is not just about nuclear reactions. It is much more general and it describes a kind of network that's called "fully connected," that is where all nodes are connected to all other nodes. In the set-up, the traps are nodes of the network, the balls are elements that trigger the connection between nodes. It is a kind of communication based on "enhanced" or "positive" feedback.

This experiment can describe a variety of systems. Imagine that the traps are oil wells. Then, the balls are the energy created by extracting the oil. And you can use that energy to dig and exploit more wells. The result is the "bell-shaped" Hubbert curve, nothing less!  You can see it in the figure above: it is the number of flying balls "produced" by the traps.

We found this kind of curve for a variety of socioeconomic systems, from mineral extraction to fisheries (for the latter, you can see our (mine and Ilaria's) book "The Empty Sea." So, the mousetraps can describe also the behavior of fisheries and have something to do with the story of Moby Dick as told by Melville.

You could also say the mousetrap network is a holobiont because holobionts are non-hierarchical networks of entities that communicate with each other. It is a kind of holobiont that exists in nature, but it is not common. Think of a flock of birds foraging in a field. One bird sees something suspicious, it flies up, and in a moment all the birds are flying away. We didn't have birds to try this experiment, but we found a clip on the Web that shows exactly this phenomenon.

It is a chain reaction. The flock is endowed with a certain degree of intelligence. It can process a signal and act on it. You can see in the figure our measurement of the number of flying birds. It is a logistic function, the integral of the bell-shaped curve that describes the flying balls in the mousetrap experiments



In Nature, holobionts are not normally fully connected. Their connections are short-range, and signals travel more slowly through the network. It is often called "swarm intelligence" and it can be used to optimize systems. Swarm intelligence does transmit a signal, but it doesn't amplify it out of control, as a fully connected network does, at least normally. It is a good control system: bacterial and ant colonies use it. Our brains are much more complicated: they have short-range connections but also long-range ones and probably also collective electromagnetic connections. 

One system that is nearly fully connected is the world wide web. Imagine that traps are people while the balls are memes. Then what you are seeing with the mousetrap experiment is a model of a meme going viral on the Web. Ideas (also called memes) flare-up on the Web when they are stimulated it is the power of propaganda that affects everybody.

It is an intelligent system because it can amplify a signal. That is that's the way it reacts to an external perturbation. You could see the mousetraps as an elaborate detection system for stray balls. But it can only flare up and then decline. It can't be controlled. 

That's the problem with our modern propaganda system: it is dominated by memes flaring up out of control. The main actors in this flaring are those "supernodes" (the Media) that have a huge number of long-range connections. That can do a lot of damage: if the meme that goes out of control is an evil meme and it implies, say, going to war against someone, or exterminating someone. It happened and keeps happening again as long as the memesphere is organized the way it is, as a fully connected network. Memes just go out of control.

All that means we are stuck with a memesphere that's completely unable to manage complex systems. And yet, that's the way the system works. It depends on these waves of out-of-control signals that sweep the web and then become accepted truths. Those who manage the propaganda system are very good at pushing the system to develop this kind of memetic waves, usually for the benefit of their employers. 

Can the memesphere be re-arranged more effectively -- turning it into a good holobiont? Probably yes. Holobionts are evolutionary entities that nobody ever designed. They have been designed by trial and error as a result of the disappearance of the unfit. Holobionts do not strive for the best, they strive for the less bad. It may happen that the same evolutionary pressure will act on the human memesphere. 

The trick should consist in isolating the supernodes (the media) in such a way as to reduce their evil influence on the Web. And, lo and behold, it may be happening: the great memesphere may be rearranging itself in the form of a more efficient, locally connected holobiont.  Haven't you heard how many people say they don't watch TV anymore? Nor do they open the links to the media on the Web. That's exactly the idea. Do that, and maybe you will start a chain reaction in which everyone will get rid of their TV. And the world will be much better. 




6 comments:

  1. The weakness in Richard Sutton's Mousetrap experiment is exactly that of the earlier encountered by Boltzmann - overlooking the initial Energy that made the whole system - a one piece....

    The West needed to realise earlier - fossil fuels shouldn't be socialised among the masses.


    Instead, extracted fossil fuels must have been kept - to the absolute minimum.

    The masses, no more than 1.5 billion then in the 1860s - at max - would have had their lives progressed organically - like how it has been evolving - since the antiquity - no harm done...

    The West itself would have had more time to understand - what's going on...

    How fossil fuels can drive the population crazy, how fossil fuels, once extracted, would never allow humans less extracting fossil fuels - until the reserves are gone...

    Shame, the West didn't take its time - before fossil fuels have hypnotised it - to go a Communist - socialising fossil fuels among the masses....

    Richard Sutton's Mousetrap should have been thought of - before the West embarked on the mass extraction of fossil fuel, not now when the reserves are almost gone...

    Controlling humans with fossil fuels - is a lose-lose endeavour - no matter how perception-control seems now doing well - for a while...

    At the end, the synthetic perception vanishes - and fossil fuels reserves - too....

    Can humans force time to go backward - and fix their biggest error of judgment - ever?

    This is exactly the question humans raised since Gilgamesh.

    How come after thousands of years and burning all fossil fuels reserves to the ground - humans still ask the same Gilgamesh's question?

    "Energy, like time, flows from past to future"

    Wailing.

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  2. So from the country that gave us the Roman Empire, crucifixion, Catholicism, burning at the stake, the Inquisition, the Mafia and Fascism, we now have a mad genius who has constructed a powerful mouse-trap bomb. Nothing good can come of this. Joe Biden must surely now add Italy to his list of terrorist states. Perhaps Ugo is planning to target some small neighbouring country such as Malta. After all, Malta is a member of the British-inspired Commonwealth of Nations, and you know how Ugo is always fulminating against "perfidious Albion" (a bit of a cheek when you consider what Italy has got up to over the centuries). And after Malta, I suspect Ugo will want to "liberate" British Indian Ocean Territory.

    As for those red, white and green subatomic particles, Ugo is behind the times. Here in perfidious Albion, I happen to own a few trillion very rare multi-coloured ones. I keep them in a jam jar and they are very valuable. I plan to sell them on eBay, but if Ugo sends me a postal order for two billion lire before the end of the week, they could be his. ;-)

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    Replies
    1. As we use to say in Italy, "Dio stramaledica gli inglesi!"

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    2. Hmm! So that must be why pop star "Savage" (Roberto Zanetti) mangled our beautiful English language in his 1983 pop song:

      "Just a random access memories of dreams
      As you're hangin' upon me, do you love melody?
      Thief of golden toys to an upset time away
      As we're human being at last we have the melody, we too."

      No, I don't know what it means either. :-(

      https://www.youtube.com/watch?v=1TymTB14iqo

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  3. Hello Ugo,
    That was a good Friday-challenge to the imagination!

    In a hardware store we need to look for items with the following properties:
    * Can store energy (or has built-in stored energy)
    * Can release energy after a trigger event
    * Can trigger the release for at least 2 items with it's embodied energy

    I think that we could do the same demonstration using matches. In 2-D or in 3-D.

    I think there are many objects with these properties.
    Would it work with bottles of thinner? Sound-triggered alarm systems?

    Or did I miss something?

    Peace,
    Goran

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    Replies
    1. Yes, matches would go off in an auto-catalytic reaction. And you can also do something similar with ice-cream sticks -- it is called the "stick bomb." Neither can generate the kind of chain reaction that the mousetrap bomb can create, the kind that can simulate an atomic explosion or the Hubbert curve. Maybe it could be done with bottles of thinner or sound triggered alarm systems? I don't know. Maybe you can think of something?

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