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Fern leaves and cauliflower curds are not fractals (2012)

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Re: Fern leaves and cauliflower curds are not fractals (2012)

#61
post #25

Earlier quoted context omitted.

You can create the same fractal in many ways. For example you get Sierpiński triangle if you repeatedly draw smaller triangles, or you can just do xor.

My favorite way to draw the Sierpinski triangle is Monte Carlo: 1. Pick a point which is in the triangle (e.g. one of the corners of the triangle). Draw that point. 2. Choose one corner of the triangle at random. 3. Move to the point half way between your current point and the chosen corner. Draw that point. 4. Repeat steps 2-3 as long as desired. Obviously this only ever reaches a countable subset of the triangle ba…

These sets of transforms are known as iterated function systems (IFS), and the algorithm dubbed "the chaos game" by Barnsley. If I recall correctly the algorithm actually distributes uniformly over a probability measure supported by the set, so for picture-making purposes it is typically done with a probability associated with each transforms chosen to even out the visitation (otherwise some details will take forever to be seen).

The whole area is a consequence of Banach's fixed point principle (a very fundamental result), with Hutchinson I think extending it to unions of contractive maps.

Math has many beautiful corners.

Re: Fern leaves and cauliflower curds are not fractals (2012)

#62

> Actual fern leaves and cauliflower curds have a very small number of anatomically variable and non-iterating bifurcations, which superficially look self-similar, but do not allow for scaling down of their structure as real fractals do. Sorry, can't help it, but really? You cannot zoom into real-life fractals infinitely like in those math animations, only a few times? What comes next? Even the coast line or mountain…

That may be true but there were lifeforms with more fractal structures like the precambrian Charnia (https://en.wikipedia.org/wiki/Charnia ) and other Rangeomorphs ( https://en.wikipedia.org/wiki/Rangeomorph ).

The main difference the author is getting at (I suspect, I'm not a biologist) is that these earlier life forms display a multilevel fractal self-similarity within their fronds, basically fronds of fronds of fronds of fronds, instead of modern plants where the fronds have structural differences like leaves/buds that keep the pattern from replicating past a certain point.

The weird thing is that as far as body plans go, a fractal shape would maximize surface area while minimizing body volume which would seem advantageous for a filter feeding organism. It's not clear why such a simple design went extinct so quickly.

Re: Fern leaves and cauliflower curds are not fractals (2012)

#63

People who are complaining about the article: There's this trope about physics and math envy, which I think ultimately boiled down an envy of the funding that physicists received in the cold war (it lead to a lot of equations in Ecology, for instance). But ignoring the reasons for math envy for a moment, there's also a push among some of the more computationally inclined to try to explain other sciences using their t…

I don't think I get your point. Especially regarding weather models. I'm pretty sure that to program good weather predictions, you need to know a lot about the mechanisms. And a prediction model can be used to test theories by comparing predictions against reality. That makes the theories falsifiable.

And what is it about comparing computational weather models to p-hacking? Good weather predictions provide value to lots of people, while p-hacking is looking for results where there are none, only benefitting the hacker.

Re: Fern leaves and cauliflower curds are not fractals (2012)

#64
post #50

Earlier quoted context omitted.

> You cannot zoom into real-life fractals infinitely like in those math animations, only a few times? The point of the paper is that these are not 'real life fractals', so your correct declaration about the obviousness of real life fractals being bounded in their depth is not relevant, and does not make this paper pointless. It's not obvious to me that fern branches are 'anatomically variable and non-iterating bifurc…

> It's not obvious to me that fern branches are 'anatomically variable and non-iterating bifurcations', rather than a recursive process that bottoms out at a size boundary. But hardly any (no?) real-life phenomena are the latter! As a mathematician, I'm as bothered by imprecise use of mathematical terminology as anyone, but, if we're going to call anything in real life a fractal, then it surely means something more l…

There were fractal body plans in the precambrian era but they went extinct pretty quickly.

https://en.wikipedia.org/wiki/Rangeomorph

Re: Fern leaves and cauliflower curds are not fractals (2012)

#65
Here's a much more interesting (popsci) article: https://www.nytimes.com/2021/07/08/science/cauliflower-fract... and the paper related to it: https://www.science.org/doi/full/10.1126/science.abg5999 Note the comment at the bottom of the article (who is the author of the posted article)

After reading a fair amount of this I'd conclude that the posted article doesn't really move science farther, it just acts as a pedantry gate.

Re: Fern leaves and cauliflower curds are not fractals (2012)

#66
post #15

> Actual fern leaves and cauliflower curds have a very small number of anatomically variable and non-iterating bifurcations, which superficially look self-similar, but do not allow for scaling down of their structure as real fractals do. Sorry, can't help it, but really? You cannot zoom into real-life fractals infinitely like in those math animations, only a few times? What comes next? Even the coast line or mountain…

Fractals don't even need to be self-similar. They just need to have fractal dimension (if you double the size of every feature - the exponent near the scaling factor must be non-integer). Self-similarity is the easiest way to make a fractal, but not the only one. In fact the idea of fractal was invented for real-life non-self-similar objects. The simple self-similar ones are just examples that are easiest to understa…

Thanks, this and the post to which you replied taught me something that I did not know. TIL...

Re: Fern leaves and cauliflower curds are not fractals (2012)

#67

People who are complaining about the article: There's this trope about physics and math envy, which I think ultimately boiled down an envy of the funding that physicists received in the cold war (it lead to a lot of equations in Ecology, for instance). But ignoring the reasons for math envy for a moment, there's also a push among some of the more computationally inclined to try to explain other sciences using their t…

I don't think I get your point. Especially regarding weather models. I'm pretty sure that to program good weather predictions, you need to know a lot about the mechanisms. And a prediction model can be used to test theories by comparing predictions against reality. That makes the theories falsifiable. And what is it about comparing computational weather models to p-hacking? Good weather predictions provide value to l…

TLDR: Math and models can aid with understanding, but fundamentally they're about divination, not explanation. And explanation is the core of science. Over application of models is as bad as p-hacking, in that false explanations for phenomena are promulgated. At least with p-hacking, one other paper can say that a correlation was not shown. Whereas with model-hacking, there is often a tendency to "tweak" the model to fit, ala the earth-centric model of the solar system with its epicycles.

> And what is it about comparing computational weather models to p-hacking?

P-hacking is just an extension of assuming p-values past a certain point are very good evidence of real-world correlation. The Princeton Engineering Anomalies Research has evidence showing human-operator specific effects on computerized random processes at the 7 sigma statistical level: https://pearlab.icrl.org/pdfs/1997-correlations-random-binar...

Do you believe that this evidence of possible psychic phenomena is real without validated mechanistic means?

> Good weather predictions provide value to lots of people, while p-hacking is looking for results where there are none, only benefitting the hacker.

Except when the p-hacking is, serendipitously, correct. P-hacked results are not necessarily wrong, they're just fraught.

> I'm pretty sure that to program good weather predictions, you need to know a lot about the mechanisms.

I'm not saying that all use of models and mathematics in science is bad. I'm saying that premature generalizations based on looks is bad.

Do you at least get my point regarding reducing the universe to a hologram or to cellular automata? Weather modeling is much better than these because of its predictive power, but most importantly because the weather modelers keep trying to refine their models based on actual mechanisms.

Knowledge of the mechanisms help guide the parameters used in the models. But the models are not the thing. The equations are not the mechanisms. And the approximations certainly aren't the thing.

And I'm sure that holograms and cellular automata are useful at times in predicting or thinking about reality, just as fractals are useful in some understanding of plants (despite not being accurate models). Just as the Earth-centric model of the solar system with its epicycles was pretty decent at predicting future positions of the planets.

Mathematical models are not the end of the scientific investigation. Mathematical models are the intersection of science (understanding of the universe) and divination (trying to predict the future). Statistics are most useful for trying to identify linkages which probably share mechanisms, or for testing a hypothesized mechanism's effect on particular parameters. In physics, equations for quantum stochastic processes does not mean we've finished with our quantum understanding of the universe.

Math is not science, it's a separate thing that helps with science. Generalized models are generalized models, not fully accurate representations.

And trying to prematurely universalize models is just as bad as p-hacking. Even worse is trying to universalize a single model idea (such as holograms, cellular automata, or fractals) to an entire field. Even if you are right, your model provides a divination understanding of the phenomena, not a scientific understanding of the phenomena.

Crap, I have some good points here, but it's probably TLDR at this point.

Re: Fern leaves and cauliflower curds are not fractals (2012)

#68

Earlier quoted context omitted.

I don't think I get your point. Especially regarding weather models. I'm pretty sure that to program good weather predictions, you need to know a lot about the mechanisms. And a prediction model can be used to test theories by comparing predictions against reality. That makes the theories falsifiable. And what is it about comparing computational weather models to p-hacking? Good weather predictions provide value to l…

TLDR: Math and models can aid with understanding, but fundamentally they're about divination, not explanation. And explanation is the core of science. Over application of models is as bad as p-hacking, in that false explanations for phenomena are promulgated. At least with p-hacking, one other paper can say that a correlation was not shown. Whereas with model-hacking, there is often a tendency to "tweak" the model to…

> Do you believe that this evidence of possible psychic phenomena is real without validated mechanistic means?

Just to add, personally I'm ambivalent on the topic.

Re: Fern leaves and cauliflower curds are not fractals (2012)

#69
post #50

Earlier quoted context omitted.

> It's not obvious to me that fern branches are 'anatomically variable and non-iterating bifurcations', rather than a recursive process that bottoms out at a size boundary. But hardly any (no?) real-life phenomena are the latter! As a mathematician, I'm as bothered by imprecise use of mathematical terminology as anyone, but, if we're going to call anything in real life a fractal, then it surely means something more l…

There were fractal body plans in the precambrian era but they went extinct pretty quickly. https://en.wikipedia.org/wiki/Rangeomorph

> There were fractal body plans in the precambrian era but they went extinct pretty quickly.

Cool! I didn't know about that.

Re: Fern leaves and cauliflower curds are not fractals (2012)

#70
post #42

Earlier quoted context omitted.

Analogies are only useful to the extent they have explanatory power. The assertion here is that this one doesn’t: there are several distinct growth mechanisms applied in sequence, not a recursive application of the same mechanism.

Different mechanisms can use the same template. The Romanesco cauliflower is so obviously self-similar that ignoring this in favor of talking about mechanisms that vary according to scale needs is missing the forest for the trees.

Biology has the concept of convergent evolution. Would you say a Thylacine is a Wolf, and that it's appropriate to treat one as the other?

Fractals are a singular example of repeating patterns, but there are additional repeating pattern types that aren't fractals. Just like Thylacines and Wolves were/are examples of apex predators, not versions of each other.

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