Plants, Math, Spirals, & the Value of the Golden Ratio

The natural world is brimming with ratios, and spirals, that have been captivating mathematicians for centuries.

1.0 Phyllotaxis Spirals

The term phyllotaxis (from the Greek phullonleaf,’ and taxisarrangement) was coined around the 17th century by a naturalist called Charles Bonnet. Many notable botanists have explored the subject, such as Leonardo da Vinci, Johannes Kepler, and the Schimper brothers. In essence, it is the study of plant geometry – the various strategies plants use to grow, and spread, their fruit, leaves, petals, seeds, etc.

1.1 Rational Numbers

Let’s say that you’re a flower. As a flower, you want to give each of your seeds the greatest chance of success. This typically means giving them each as much room as possible to grow, and propagate.
Starting from a given center point, you have 360 degrees to choose from. The first seed can go anywhere and becomes your reference point for ‘0‘ degrees. To give your seeds plenty of room, the next one is placed on the opposite side, all the way at 180°. However the third seed comes back around another 180°, and is now touching the first, which is a total disaster (for the sake of the argument, plants lack sentience in this instance: they can’t make case-by-case decisions and must stick to one angle (the technical term is a ‘divergence angle‘)).
Rational Numbers.gif
Phyllotaxis Study: 180° (see corn leaves), 90° (see mint leaves),  and 72° (see gentiana petals)
Next time you only go to 90° with your second seed, since you noticed free space on either side. This is great because you can place your third seed at 180°, and still have room for another seed at 270°. Bad news bears though, as you realise that all your subsequent seeds land in the same four locations. In fact, you quickly realise that any number that divides 360° evenly yields exactly that many ‘spokes.’
Low Spokes.jpg
Phyllotaxis Study – 1,000 Seed Spread: 45°, 36°, and 20°
Phyllotaxis Spoke Chart.jpg
Note: This is technically true with numbers as high as 120, 180, or even 360(a spoke every 1°.) However the space between seeds in a spoke gradually becomes greater than the space between spokes themselves, leaving you with one big spiral instead.
High Spokes
Phyllotaxis Study – 1,000 Seed Spread: 8°, 5°, and 2°

1.2 Irrational Numbers

These ‘spokes’ are the result of the periodic nature of a circle. When defining an angle for this experiment, the more ‘rational’ it is, the poorer the spread will be (a number is rational if it can be expressed as the ratio of two integers). Naturally this implies that a number can be irrational.
Sal Khan has a great series of short videos going over the difference between the two [Link]. For our purposes, the important take-aways are:
-Between any two rational numbers, there is at least on irrational number.
Irrational numbers go on and on forever, and never repeat.
You go back to being a flower.
Since you’ve just learned that an angle defined by a rational number gives you a lousy distribution, you decide to see what happens when you use an angle defined by an irrational number. Luckily for you, some of the most famous numbers in mathematics are irrational, like π (pi), √2 (Pythagoras’ constant), and e (Euler’s number). Dividing your circle by π (360°/3.14159…) leaves you with an angle of roughly 114.592°. Doing the same with √2 and e leave you with 254.558° and 132.437° respectively.
Irrational Numbers.gif
Phyllotaxis Growth Study: Pi, Square Root of 2, and Euler’s Number
Great success. These angles are already doing a much better job of dispersing your seeds. It’s quite clear to you that √2 is doing a much better job than π, however the difference between √2 and e appears far more subtle. Perhaps expanding these sequences will accentuate the differences between them.
Expanded Irrational Numbers.jpg
Phyllotaxis Study – 1,000 Seed Spread: Pi, Square Root of 2, and Euler’s Number
It’s not blatantly obvious, but √2 appears to be producing a slightly better spread. The next question you might ask yourself is then: is it possible to measure the difference between the them? How can you prove which one really is the best? What about Theodorus’, Bernstein’s, or Sierpiński’s constants? There are in fact an infinite amount of mathematical constants to choose from, most of which do not even have names.

1.3 Quantifiable irrationality

Numbers can either be rational or irrational. However some irrational numbers are actually more irrational than others. For example, π is technically irrational (it does go on and on forever), but it’s not exceptionally irrational. This is because it’s approximated quite well with fractions – it’s pretty close to 3+1⁄7 or 22⁄7. It’s also why if you look at the phyllotaxis pattern of π, you’ll find that there are 3 spirals that morph into 22 (I have no idea how or why this is. It’s pretty rad though).
00 Pi Voronoi.jpg
Phyllotaxis Voronoi Diagram – Proximity to Closest Neighbour: Pi
Voronoi Proximity Legend.jpg
Generating a voronoi diagram with your phyllotaxis patterns is a pretty neat way of indicating exactly how much real estate each of your seeds is getting. Furthermore, you can colour code each cell based on proximity to nearest seed. In this case, purple means the nearest neighbour is quite close by, and orange/red means the closet neighbour is relatively far away.
e and root 2 Voronoi Diagrams.jpg
Phyllotaxis Voronoi Diagram – Proximity to Closest Neighbour: Square Root of 2, and Euler’s Number
Congratulations! You can now empirically prove that √2 is in fact more effective than e at spreading seeds (e‘s spread has more purple, blue, and cyan, as well as less yellow (meaning more seeds have less space)). But this begs the question: how then, can you find the most irrational number? Is there even such a thing?
You could just check every single angle between 0° and 360° to see what happens.
This first thing you (by which ‘you,’ I mean ‘I’) notice is: holy cats, that’s a lot of options to choose from; how the hell are you suppose to know where to start?
The second thing you notice is that the pattern is actually oscillating between spokes and spirals, which makes total sense! What you’re effectively seeing is every possible rational angle (in order), while hitting the irrational one in between. Unfortunately you’re still not closer to picking the most irrational one, and there are far too many to compare one by one.

1.4 Phi

Fortunately you don’t have to lose any sleep over this, because there is actually a number that has been mathematically proven to be the most irrational of all. This number is called phi (a.k.a. the Golden/Divine + Ratio/Mean/Proportion/Number/Section/Cut etc.), and is commonly written as Φ (uppercase), or φ (lowercase).
It is the most irrational number because it is the hardest to approximate with fractions. Any number can be represented in the form of something called a continued fraction. Rational numbers have finite continued fractions, whereas irrational numbers have ones that go on forever. You’ve already learned that π is not very irrational, as it’s value is approximated pretty well quite early on in its continued fraction (even if it does keep going forever). On the other hand, you can go far further in Φ‘s continued fraction and still be quite far from its true value.

Source:
Infinite fractions and the most irrational number: [Link]
The Golden Ratio (why it is so irrational): [Link]

Since you’re (by which ‘you’re,’ I mean I’m) a flower (by which ‘a flower,’ I mean ‘an architecture student’), and not a number theorist, it’s less important to you why it’s so irrational, and more so just that it is so. So then, you plot your seeds using Φ, which gives you an angle of roughly 137.5°.
Phi.gif
Phyllotaxis Study: The Golden Ratio
It seems to you that this angle does a an excellent job of distributing seeds evenly. Seeds always seem to pop up in spaces left behind by old ones, while still leaving space for new ones.
Golden Ration Spreads.jpg
Phyllotaxis Voronoi Diagram – Proximity to Closest Neighbour – 1,000 Seed Spread: The Golden Ratio
Expanding the this pattern, as well as the generation of a voronoi diagram, further supports your observations. You could compare Φ‘s colour coded voronoi/proximity diagram with the one produced using √2, or any other irrational number. What you’d find that Φ does do the better job of evenly spreading seeds. However √2 (among with many other irrational numbers) is still pretty good.

1.5 The Metallic Means & Other Constants

If you were to plot a range of angles, along with their respective voronoi/proximity diagrams, you can see there are plenty of irrational numbers that are comparable to Φ (even if the range is tiny). The following video plots a range of only 1.8°, but sees six decent candidates. If the remaining 358.2° are anything like this, then there could easily well over ten thousand irrational numbers to choose from.
It’s worth noting that this is technically not how plants grow. Rather than being added to the outside, new seeds grow from the middle and push everything else outwards. This also happens to by why phyllotaxis is a radial expansion by nature. In many cases the same is true for the growth of leaves, petals, and more.
It’s often falsely claimed that the Φ shows up everywhere in nature. Yes, it can be found in lots of plants, and other facets of nature, but not as much as some people might have you believe. You’ve seen that there are countless irrational numbers that can define the growth of a plant in the form of spirals. What you might not know is that there is such as thing as the Silver Ratio, as well as the Bronze Ratio. The truth is that there’s actually a vast variety of logarithmic spirals that can be observed in nature.
Mathematical Constants Phyllotaxis.jpg
Phyllotaxis Voronoi /Proximity Study: Various Known Mathematical Constants

Source:
The Silver Ratio & Metallic Means: [Link]

 

1.6 Why Spirals?

A huge variety of plants have been observed to exhibit spirals in their growth (~80% of the 250,000+ different species (some plants even grow leaves at 90° and 180° increments)). These patterns facilitate photosynthesis, give leaves maximum exposure to sunlight and rain, help moisture spiral efficiently roots, and or maximize exposure for insect pollination. These are just a few of the ways plants benefit from spiral geometry.
Some of these patterns may be physical phenomenons, defined by their surroundings, as well as various rules of growth. They may also be results of natural selection – of long series of genetic deviations that have stood the test of time. For most cases, the answer is likely a combination of these two things.
In some of the cases, you could make an compelling arrangement suggesting that these spirals don’t even exist. This quickly becomes a pretty deep philosophical question. If you put a series of points in a row, one by one, when does it become a line? How close do they have to be? How many do you have to have? The answer is kinda slippery, and subjective. A line is mathematically defined by an infinite sum of points, but the brain is pretty good at seeing patterns (even ones that don’t exist).

M.C. Escher said that we adore chaos because we love to produce order. Alain Badiou also said that mathematics is a rigorous aesthetic; it tells us nothing of real being, but forges a fiction of intelligible consistency.

I N T I

0-01

Philosophical Statement:

Inti: The Incan Sun God, his face portrayed as a gold disk from which rays and flames extended. Inti is the Sun and controls all that implies: warmth, light and sunshine. During the festival of Inti Ramyi, held during the Summer Solstice, Inti is celebrated with much drinking, singing and dancing – special statues are made of wood are burned at the end of the festival. This sculpture is an extended physical manifestation of this; decadent ritualism and a spiritual experience.

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Inti incorporates 288 petals are self-assembled into 12 concentric rings, with each petal representing the hours of the day and each ring every month of the year. These are held together using mirror polished circular brackets, designed to catch the light and reflect circles of sunlight around the structure interior. Inti’s focus is the sunrise; as the sun rises on the playa, Inti is designed to catch the light at this precise moment and funnel through the piece, enveloping and bathing the burners inside with it’s warmth and spirit.

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3-01-01

Timber Wave by Henry Turner

01 Day

Philosophical Statement:

‘Timber-Wave’; a plywood instillation emerging and crashing on to the desolate Black Rock Desert. This breaking wave a remnant of the retreating Quinn River, draws on imagery of both waves and dunes provoking thoughts of the original Burning Man Beach Parties and surfing counter culture. Simultaneously the design evokes concepts of the Silk Road as a mirage of a giant wave appearing from across the playa to be discover by wondering burners.

The design of the Timber Wave was driven by creating an interactive environment. In daytime, people are encourages to climb and search between the interwoven plywood structure. Open sun soaked communal areas create areas for group contemplation. Solitary areas for single travelers have also been designed as places of refuge from the intense sun, wind and dust storms hoping to encourage serendipity. At night the wave truly come alive as a monument to the sea. Bathed in varying blue tones of color the spectacular structure is a mysterious beacon within the dark playa.

02 Night

Physical Statement:

‘Timber-Wave’  structure consists of 3 layers of 12 intersecting plywood ribbons.  Each ribbon consists of a varying number of water bent plywood components con-caving and con-vexing together forming a rigid series of tensioned and compressed sections.  The result is a homogeneous structure creating a beautiful ergonomically sized spaces. Each ribbon a series of circular penetrations in the form of an abstracted water pattern.  Creating foot and hand holes for climbing as well as allowing dramatic shadows to be cast throughout the structure and across the playa. At night the penetrations allow the lighting of the instillation to spill across the playa and between the layers of the structure.

03 Day

04 Internal Image

Axo.indd

1:20 Scale Model

01 Portfolio Review.indd

Link: issuu.com/henryturner/docs/portfolio?e=0/6863548

Three-Dimensional Mid-Air Acoustic Manipulation

Lying somewhere between science and art, University of Tokyo scientists Yoichi Ochiai,  Takayuki Hoshi and Jun Rekimoto use precision acoustics to bring the beauty of sound waves to life in three dimensions.

More information here from the University of Tokyo, Nagoya Institute of Technology

Polystyrene beads self organising in mid air

3rd October 2013 Tutorials

Back in our studio and excited to see how students are tackling the brief this year. Here are some pictures showing the different systems that students chose for brief01 and some of the models that are already being produced.

DS10 studio all buzzing
DS10 studio all buzzing
Andrei Jippa is 3D printing radiolarias with his RepRap
Andrei Jippa is 3D printing radiolarias with his RepRap
String vibration experiments by Garis Lu
String vibration experiments by Garis Iu
Henry Turner looking at microscopic images of sea urchins
Henry Turner looking at microscopic images of sea urchins
Origami Folding from Sarah Shuttleworth
Origami Folding from Sarah Shuttleworth
John Konings looking at bamboo structures
John Konings looking at bamboo structures

The Burning Ship Set

Arthur C. Clarke’s documentary on Fractals:

A basic set with fractal behaviour is the set of Complex numbers (C):

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No matter how much one zooms in or out, the set is self-similar with infinite detail.

The typical fractal sets (Mandelbrot, Julia, Fatou) follow a pattern of 3 infinities: an infinite number of points is run an infinite number of times through a recursive polynomial and it will/will not reach infinity:

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To make the step to 3d, the major issue is that the 2d rules cannot be generalized  because there is no corresponding set of numbers for 3d space. 1d space has Real numbers, 2d space has Complex numbers, but there is no 3d equivalent. However, Quaternions (hypercomplex numbers) are a theoretical set of points corresponding to a 4d space. Therefore there are two possible approaches: a) Define a three dimensional set of points in polar coordinates and switch them back to a cartesian coordinates in order to build it in computer space. b) Build a theoretical 4d fractal using hypercomplex numbers and cast its 3d shadow in 3d.Image

Either way, results are similar:Image

Dealing with infinite numbers, infinite iterations and infinite sets of points, computation times become an issue. One way around this is to build ray-traced images estimating distances to a virtual fractal (not physically storing the points of the fractal in memory):ImageImage

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The image above is magnified ~3.10e13 times. In other words, presuming the size of the sectional model is 1m, it scaled up to roughly the size of the Solar System.

Building 3d models in computer space is slightly trickier because of the huge number of points involved to define even a limited section of a fractal. The issue is to define an algorithm for the correct order of the points in order to build a mesh. A rather neat solution is to ray-trace consecutive sections through a fractal (ray-tracing involves a Z-buffer anyway) and work from there. Here is an example (a 38,000,000 face-mesh obtained from 1,000 sections):Image

An important tool in exploring 3d fractals is building Julia sets (the only difference is that they use a constant increment at each iteration rather than the initial step):

Software used for my project: Processing, ImageJ FIJI, MeshLab, Netfabb Studio, Jesse’s MandelBulb 3D, Autodesk 3dS Max, Chaos Pro, Adobe Premiere.

The Nature of Code

Here is the book that I kept mentionning in the tutorial: The Nature of Code by Daniel Schiffman

The Nature of CodeThe book explains many algorithm that attempt to reproduce natural systems (including swarms and fractals) using Processing, the java-based scripting interface.

You can download the book and make a donation or buy the hard copy. Try some examples, register to the Processing forum and to StackOverflow.com. Ask for help on the Processing IRC Channel.

For some example, you will need to need to download the Toxiclibs library and you might want to use the Eclipse IDE to speed up your workflow. You can also follow the great Plethora-Project.com tutorials by Jose Sanchez.