# Tag: plants

## 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

*phyllotaxis*(from the Greek

*phullon*‘

**leaf**,’ and

*taxis*‘

**arrangement**) 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

**giving them each as much room as possible to grow, and propagate**.

**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*‘)).

**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.’**

### 1.2 Irrational Numbers

**nal’ it is, the poorer the spread will be (**

*ratio***a number is rational if it can be expressed as the ratio of two integers**). Naturally this implies that a number can be irrational.

**Irrational numbers go on and on forever**, and never repeat.

**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

*(pi),*

**π***(Pythagoras’ constant), and*

**√2***(Euler’s number). Dividing your circle by*

**e***(360°/3.14159…) leaves you with an angle of roughly*

**π****114.592°**. Doing the same with

*and*

**√2***leave you with*

**e****254.558°**and

**132.437°**respectively.

*is doing a much better job than*

**√2***, however the difference between*

**π***and*

**√2***appears far more subtle. Perhaps expanding these sequences will accentuate the differences between them.*

**e***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.*

**√2**### 1.3 Quantifiable irrationality

**some irrational numbers are actually more irrational than others**. For example,

*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).*

**π****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.

**is in fact more effective than**

*√2**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?*

**e****every single angle between 0° and 360°**to see what happens.

**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

**the most irrational of all**. This number is called

*(a.k.a. the Golden/Divine + Ratio/Mean/Proportion/Number/Section/Cut etc.), and is commonly written as*

**phi***(uppercase), or*

**Φ***(lowercase).*

**φ****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

*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*

**π***‘s continued fraction and still be quite far from its true value.*

**Φ***Source:*

*Infinite fractions and the most irrational number: [Link]*

*The Golden Ratio (why it is so irrational): [Link]*

*, which gives you an angle of roughly*

**Φ****137.5°**.

**Seeds always seem to pop up in spaces left behind by old ones, while still leaving space for new ones**.

*‘s colour coded voronoi/proximity diagram with the one produced using*

**Φ***, or any other irrational number. What you’d find is that*

**√2****However**

*Φ*does do the better job of evenly spreading seeds.*(among with many other irrational numbers) is still pretty good.*

**√2**### 1.5 The Metallic Means & Other Constants

*(even if the range is tiny). The following video plots a range of only*

**Φ****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.

**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.

*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 mi*

**Φ****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.

*Source:*

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

### 1.6 Why Spirals?

**These patterns facilitate photosynthesis, give leaves maximum exposure to sunlight and rain, help moisture spiral efficiently towards roots, and or maximize exposure for insect pollination**. These are just a few of the ways plants benefit from spiral geometry.

**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.

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**.

## Urban Aquaponics, Internet and Food

**“My garden is sending tweets!” Eric Maundu**

Just came across this amazing video in which Eric Maundu talks about his start-up “**Kijani Grows**” (“Kijani” is Swahili for green), a small startup that designs and sells custom aquaponics systems for growing food using cheap technology including arduino boards. Toby and I often talk about “closed loop systems”, this is a great example of one.

*“The land in West Oakland where Eric Maundu is trying to farm is covered with freeways, roads, light rail and parking lots so there’s not much arable land and the soil is contaminated. So Maundu doesn’t use soil. Instead he’s growing plants using fish and circulating water. It’s called aquaponics- a gardening system that combines hydroponics (water-based planting) and aquaculture (fish farming). It’s been hailed as the future of farming: it uses less water (up to 90% less than traditional gardening), doesn’t attract soil-based bugs and produces two types of produce (both plants and fish). **Aquaponics has become popular in recent years among urban gardeners and DIY tinkerers, but Maundu- who is trained in industrial robotics- has taken the agricultural craft one step further and made his gardens smart. Using sensors (to detect water level, pH and temperature), microprocessors (mostly the open-source Arduino microcontroller), relay cards, clouds and social media networks (Twitter and Facebook), Maundu has programmed his gardens to tweet when there’s a problem (e.g. not enough water) or when there’s news (e.g. an over-abundance of food to share).*

*Maundu himself ran from agriculture in his native Kenya- where he saw it as a struggle for land, water and resources. This changed when he realized he could farm without soil and with little water via aquaponics and that he could apply his robotics background to farming. Today he runs Kijani Grows (“Kijani” is Swahili for green), a small startup that designs and sells custom aquaponics systems for growing food and attempts to explore new frontiers of computer-controlled gardening. Maundu believes that by putting gardens online, especially in places like West Oakland (where his solar-powered gardens are totally off the grid), it’s the only way to make sure that farming remains viable to the next generation of urban youth.”*