Random Walk 2.4: Rock towers, Funding lotteries, Ecology in Subnautica


Hello, and welcome to Random Walk, a sciencey podcast where we take multiple steps of unit length, each with directions selected independently from the previous step. I’m your host Adam Fortais.

This week’s random walk comes from a place near and dear to my heart; polymer physics. Polymers are basically any molecules that consist of repeating units. Plastics and rubbers are everyday examples, where the base unit is something small and simple, but hundreds or thousands of these “monomers” are all linked together in a long chain. Another, sometimes overlooked polymer is DNA. It too, is just a long chain of repeating units, just these ones code for stuff (don’t get me started on polymers as information storage devices, that’s a whole other can of worms). Speaking of worms, a bulk of polymer, on the molecular level, looks kind of like a can of worms. Each polymer molecule is kind of like this big long string, or lump of cooked spaghetti that gets tangled up with all of the other big long tangles of spaghetti. Now, if you think about eating spaghetti, the longer the noodle, the harder it is to pull a single noodle off the plate. Typically you’ll get a wad of noodles, since they all tend to get tangled up. On the other hand, risotto, or those short, rice-looking noodles don’t get tangled because they aren’t very long. The same sort of thing happens with polymers, and this is one aspect of the polymer that determines if the material will be all soft, goopy, and even liquid-y like warm silly putty, or if it will be hard and rigid like the egg silly putty comes in. Now, another part of this model is how the lengths of polymers are distributed in the bulk. You can have a big long polymer, but if it tightly coils around itself in little globules, it won’t get all that tangled up with the other globs. So, part of understanding what a bulk of polymer will look like is determined by the amount of space a single polymer chain will take up. We can model this as a Random Walk. 

Picture our drunken walker from a few weeks back. He steps out of the bar and can either turn left or right with equal probability. He takes a step, and has the exact same problem. Left or right. He steps again, and the same decision. Well, let’s alter this model a bit and say he can walk north, south, east, or west. Also, let’s tie a string to him and let him leave a trail. This string is the polymer chain, and the trail it leaves is a good simulation of the lump of spaghetti that is a single polymer chain. We can make the model better by introducing rules, like “the walker has to avoid crossing his own string”, or “he has to follow google maps and only stay on sidewalks, but that’s the jist! 


This week, we:

  • Are building towers out of rocks, because the US military wants us to!
  • Buying lottery tickets instead of writing grant proposals – it actually might be the best way to do it!
  • And of course, Jessie is back talking ecology on Gamer’s Guide to Ecology. This week, we’re starting in on the deep sea planet of Subnautica.

But first: This podcast is brought to you by scientificanada.ca . The goal of scientificanada is to get real science to real people, which we do by producing entertaining and informative content about research, academia, and being a curious nerd. A big part of our thing is finding and promoting new projects and new voices with financial support and expertise. If you have an idea for a project, we’d love to hear from you. Head to scientificanada.ca to see some of the shows and articles we’ve helped with, and if you want to discuss details, you can find me on twitter at AdamFortais or email me at fortaisadam@gmail.com . Support for our projects comes from our generous and very very smart patreon subscribers. Find out more about how you can help us with our next projects over at patreon.com/scican . Thanks!

**Fade music out**

Block One (C): Gamer’s Guide to Ecology: Subnautica 1 

Block Two (R): Tie a yellow ribbon ‘round a pile of rocks. 

It Looks Loopy, But It Works | College of Engineering

This week I spent some time with a new article from the Holmes lab at Boston University. They do a lot of work with granular material like rocks and soil, and as far as I know kind of coined the term “elastogranularity”. One of the first science articles I ever wrote was about a Holmes paper, where they looked at the way a flexible rod would bend and buckle when inserted into a chamber filled with different sized spheres. The analogy here is that a root growing into soil. What they found was that this simple model experiment replicated a lot of the sorts of soil-root behaviors we have come to expect… here’s an excerpt from my original post

How an elastic beam deforms under load has been a question for as long as there have been engineers to ask it. In some cases, the force on a beam is approximated as a single point. For example, if a diving board is large enough, a diver at the end can be treated as a point mass on the beam. Another common approximation is to consider the force to be a continuous pressure along its length. Treating wind that bends a tree branch as a continuous pressure along the branch’s length is much simpler than adding up the force from every molecule of air on the branch. However, consider the case of a root growing into a granular material like soil. As the root burrows through the soil it will bend due to varying point-like forces along its length. The result is a branching and twisting root system that tries to grow along the path of least resistance. An example of the diversity in plant root morphologies is shown in Figure 1 and gives a sense of how complicated and interesting the physics behind this growth can be. 

This system bears a striking resemblance to that of plant roots growing into the soil and could be useful in understanding how environmental pressures cause plant root systems to evolve. For example, cacti need to absorb as much water as they can from their environment. One way of accomplishing this is to increase the surface area of the root system by growing wide and close to the surface, rather than deep, in order to collect water from a larger area. By developing thin roots that buckle before they can deeply penetrate the soil, many cacti are able to produce the shallow, wide-reaching roots system they need to find water.

This new article follows the granular material trend, but … actually, it kind of uses all of the same materials, but in completely different ways. In this paper, they attempt to build the tallest stable tower out of granular material, something strong enough that a grad student could stand on it, for example. You could pile rocks into a mound, but that’s not very efficient. Instead they use elastic loops as a method to stabilize \columns\ of rocks, pebbles, m&ms… etc. Think of it as a series of belts that wrap around the column. That’s all it takes. No other structural support needed. 

So a natural question to ask is, how many of these loops do we need? How far apart can the loops be from each other to keep a column stable? The answer depends on the types of grains or rocks you use, and the type of loops. In general, the more spherical and smooth the rocks are, the harder it will be to stabilize the column. Also, the more flexible the loops, the closer they need to be to each other. However, irregular-shaped rocks will be able to “lock in” to each other, allowing for greater stability. Likewise, a stiffer loop means the outward pressure from the column attempting to fall apart will have a harder time pushing the loops out of their way. 

This brings up an interesting point relating to their analysis. They ran actual experiments, but they also presented a fairly simple but accurate model that was able to predict their results. One of the cool things about the model was how they treated the granular material the columns were made from. Most importantly, they made the assumption that the granular materials would behave much like a fluid. Imagine standing on a can of coke or something. The “hydrostatic pressure” in the can increases as you try to squish the can down, and if it can’t go down, it will try to go out the sides of the can. They used this same idea to model the way the granular material would try to “escape” these columns. Of course they had to include a few small changes here and there, but otherwise, the analogy worked for them. 

So why do all of this? Well, it seems like it could have some promise as a technique for building structures out of debris. In Boston University’s press release the author made note that the project was funded by a US Military grant (which is not uncommon, they fund a lot of fundamental research), and then painted a picture of a post-bombing debris field where the survivors need to rebuild quickly. Pretty grim. I much prefer Doug Holmes’ vision, 

Eventually, Holmes would like to see this minimalist technology applied to more ambitious temporary structures, shoring up roads or sea walls in ways that don’t butt heads with nature.

“We could think about not using ropes at all,” Holmes says. “Maybe we should use the roots of growing materials to stabilize structures to prevent erosion, from wind or water. To have some natural component that could help them be self-healing and adaptable to changes in the land. There are a ton of ways we could make these temporary structures permanent, but I think that harmonious approach is more compelling.”

Block Three (O): Funding via lottery? Is it more equitable?

Science funders gamble on grant lotteries

I was just reminded the other day of a story Nature News ran a while back about Funding Lotteries. I’m not sure why it was on my mind recently, maybe because I’m in the middle of applying for a whole wack of grants and fellowships right now. But the idea is, traditional granting processes, which generally rely on committees reviewing and ranking applications manually, take a lot of time, are a lot of work, and are rife with unfairness and bias despite most agency’s attempts at mitigating it. For instance, take a few other Nature News headlines:

Male researchers’ ‘vague’ language more likely to win grants

Gender bias goes away when grant reviewers focus on the science

Racial bias continues to haunt NIH grants

Thousands of grant peer reviewers share concerns in global survey

So basically, the idea is that once applications meet a certain quality threshold, they are thrown in a hat. From there, a certain number of applications are chosen at random to receive the awards. 

Another benefit of this type of system is that it cuts down on labor on all sides. For instance, I can’t remember the last time my poor supervisor had a chance to get in the lab. For most of these researchers, they got into academia because they loved doing science. That manifests itself in all sorts of different ways, but preparing grant proposals and serving on (often) volunteer committees is not the most beloved part of the job. Since a lot of the burden of decision is taken off the shoulders of reviewers, applications don’t need to be as detailed, saving the researcher time and energy. Another often overlooked side of this coin too, is a young researcher’s obligation to teach. All of this adds up to a lot of non-research work a young scientist needs to get done at likely the most precarious point of their career – when they are building towards long-term grants and tenure. 

There are a few caveats that I’m sure are decided on an agency by agency basis, but here are some of the details I’d be interested in hearing about.

*Should be for exploratory research only maybe?

*Could include an approximate ranking and weighting bias?

* Apply the random process to only the “mid-level” applications? Homerun applications that are head and shoulders above the rest can maybe get the pass right away?

Problems : could \feel\ bad, man. But you know what feels worse? Pursuing a career where you are disadvantaged for just existing as you are. Suck it up.

Maybe you end up with a few too many people doing the same things?

My instinct with this sort of thing is that we should analyze its merits objectively, and quantitatively if possible. Of course, quantifying what is “equitable” comes with its own sets of issues, but in a sense, the main idea behind this lottery system is to take personalities, and in fact, the individual out of the process completely. I think a lot of proponents and critics would say the most important thing in awarding grants is that they are awarded for science. Never the less, it is interesting and probably informative to investigate how researchers \feel\ about these types of processes. A recent study in Research Evaluation (a journal I’d not heard of) by Axel Phillips said the following:

A recent survey offers a more differentiated picture (Liu et al. 2020) among scientists who applied for the randomly allocated Explorer Grant from the Health Research Council (HRC) in New Zealand. The study reveals that the majority of applicants found it an acceptable method for distributing the Explorer Grant but they were indecisive regarding other grant types. Based on these findings, the authors suggest that scientists are more supportive of random approval if grants are small and target more risky research. However, participants also disclosed that they are only positive about selecting proposals by lot if certain condition are met, such as that all proposals are ‘of equal merit’, ‘deemed worthy enough’ or ‘reach the threshold requirements’ (Liu et al. 2020: 4). Interestingly, investigators recognized these concerns but did not progress to analyzing them systematically.

This study was aimed at understanding researchers’ feelings about the process. While I don’t think any quantitatively useful results are going to come from interviewing 32 German researchers on how they feel about grant lotteries, the study is certainly useful as a way to crowdsource ideas on how to run these programs and potential issues to look for. In particular, several researchers pointed out a quality of life enhancement that I wouldn’t have considered initially,

‘But, of course, I personally would want to know at some point as far as my proposal whether it was chosen randomly or selected’. (20, physical science, senior researcher, 92)

‘But then I would want to hear afterwards that it wasn’t an inherent technical problem but that I just didn’t have any luck in the random selection’. (16, life science, senior researcher, 128)

I’m not sure if I agree with this being a part of the process, but I understand where the idea comes from. I would rather know if there was a fundamental issue with my application, if I was pitching nonsense, or if I just need to try again next year. On the other hand, scientists are amazing at coming up with absurd metrics to differentiate themselves, so I wouldn’t be surprised to see CVs adding “selected recipient “ appended to lists of awards and “awarded at random” being omitted. 

So, what do you think? Should randomized lotteries be included in grant decisions? How would you feel getting turned down for an award because your number didn’t come up? How about not knowing if you lost out for a reason or not? What would be your concerns with such a process? Let me know on Twitter @AdamFortais

**Outro music**

That’s it for this episode. If you have comments or questions, find me on Twitter at AdamFortais or email me at fortaisadam@gmail.com

Find more of Jessie de Haan on Twitter @deHaanJ , and make sure to follow them on Twitch at justjessieD.  

Our music was provided by my friends from the band Boonie. Find them at boonie.rocks .

 If you liked the show, share it with a friend. We are on all streaming platforms and youtube, just look for scientificanada . 

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See ya later! 

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