So….another blog!

I don’t whether today to write about logic, codes, symmetry or the Fibonacci sequence. I think, seeing as I put it off last time, I should do symmetry, but I know we will be doing the Fibonacci sequence in maths tomorrow, and I’m quite keen on seeing if I can pre-empt my lecturer….therefore, I think I’ll start with the Fibonacci sequence, then move onto symmetry….

So. In the late 12th century, a dude named leonardo of pisa or Fibonacci for short (i can’t remember why) decided he wanted to know how many rabbits he would have if he started with a certain amount.

I’m not entirely certain why he wanted to do it, however, in terms of the mathematical bunny leaps that have come from it, I’m fairly glad that he did!

As with most mathematicians, he decided to skirt certain issues and start at a very simple base to get a rough idea of the pattern that ran through the bunny population. He therefore started off with a couple of assumptions:

Firstly, rabbits don’t die.

Secondly, every female has only one baby every month.

Thirdly, except for the first couple, there are always more females than males.

So he started with one rabbit.(female)

And got bored waiting for it do something.

So he got another one. (male)

after one month, the two rabbits had another rabbit. (female)

Now the one male rabbit was happy. So he did what most males love, and the following month, there were two new babies, one male, one female.

all three females gave birth the following month, resulting in 8 rabbits. There are now five females, three males, so the next month there were 13 rabbits, 8 female, 5 male, etc….

that’s a pretty rough outline of the story, and one that isn’t completely true. The most important part of this story is the pattern: 1 rabbit, 1 rabbit, 2 rabbits, 3 rabbits, 5 rabbits, 8 rabbits, 13, 21, 34, 55, 89, 144….

So how do you get this pattern?

Take any number in the pattern, add the previous number to it, and you will get the following number. So to get 13, you add 8 and 5. there are formulas for working out how many ‘rabbits’ there are after so many ‘months’, but I won’t put those into this blog.

Soubtless some of you are going “ok….there’s a pattern….so what?” well, patterns are important things!!! If there’s a pattern, THERE’S A PATTERN, which generally means there is some interesting maths going on somewhere…

so let’s have a closer look at this pattern: 1,1,2,3,5,8,13,21,34,55,89,144,233,377,610….

now have a look at the ratio’s between these numbers: 1/1 =1

2/1 =2

3/2 =1.5

5/3 =1.6666….

8/5 =1.6

13/8 =1.625

21/13= 1.61528462…

etc. the higher the pair of numbers you use, the closer this ratio gets to a very special number, which is called the golden ratio, and is approximately equal to 1.618(rounded to 3 decimal digits)

It is here I must take a breath, as the branches I could take you down are everywhere. The golden ratio is a truly important number, it appears everywhere, in your body, in beauty, in music, nature, shells….almost everything in nature links to this number.

But anyways, let me now tell you about some of the more interesting things about the golden ratio.

firstly, it is easiest to approximate the golden ration by using(sqrt(5)+1)/2. as it is an irrational number, it goes on forever, so we can never get it exactly, which is why we use it’s abbreviated form, 1.618, as this is a much ‘nicer’ number to use when doing calculations. It is also denoted by the Greek letter phi, and often called by such.

as stated above, it appears everywhere…so let’s start with a pineapple (we have to take one to class tomorrow…)

Count the ‘points’ in one clockwise spiral, and the points in one counter clockwise spiral. You will find that the number of points in each spiral will be a Fibonacci number, normally 5,8 or 13-but never 5 and 13, it will always be two consecutive numbers. in other words, the ratio between the spirals approximates the golden ratio.

it’s marvellous fun telling kids to look for a four leaf clover – they’re not very likely to find one. Why? Because four is not a fibonacci number. Seriously. That’s the reason.

now, nature is not saying “oh, four isn’t a Fibonacci number, therefore we can’t have that many leaves/points/ whatever”. people are still searching to find out why this number is so important to nature – for example, why not use a nice number like 1.6 exactly? – and there are some ideas I’ve heard about, such as claiming that the angles that the leaves make to the stem are arranged in the golden proportion to each other, resulting in the fourth leaf being over shadowed by the 6th leaf, therefore causing the 4th to die, resulting in only five. But I did a couple of calculations, and this doesn’t seem to be entirely true, so I will have to keep looking.

Some people claim that the golden ratio was used in the building of the pyramids. However, others say that it is just the fact that the golden ratio is so common that it crops up in measurements, as there is no record of the golden ratio from Egyptian times (it was first mentioned by the Greeks, popularised by Fibonacci). All that I can tell you is that it does seem to crop up almost everywhere, but what I find incredibly interesting is it’s relationship to beauty.

First, let’s start with a rectangle. Draw a rectangle of width 1, and length 1.618.Note that the relationship between the width and length is 1.618. Now, cut a square out of this rectangle with area 1 square unit. You will be left with a rectangle of 1 X 0.618. The relationship between the width and length of this new rectangle, is still 1.618. And you can keep doing this, endlessly, and each time, you will be left with a rectangle whose width and length are in the proportion of 1.618…which is fairly cool!

This rectangle is called the golden rectangle.

Now, I hope you remember some algebra from high-school.

If you want to find a number (lets call it the classic *x*) such that 1+1/*x*=*x* (or *x*^{2}–*x*-1=0), you find that the answer is phi. This explains why the rectangle cutting works, but I’ll let you try and figure that one out 😛

The rectangle is the first of the geometric shapes that can be drawn in a ‘golden proportion’, but any shape you can think of will have a golden ratio version of it (google it). The golden rectangle, triangle, cross, star, pentagon, spiral etc are generally found to be most ‘pleasing’ to the eye. why? I don’t know. The only common thing between them is this ratio, but you can test it for yourself by drawing a few or googling them and deciding which one you like the most. You may find that you don’t like the ‘golden’ one, but it is a general statement 🙂

Now, the final bit. You need a tape measure.

First, measure your arm, from fingertip to shoulder, then fingertip to elbow. Take the first, divide it by the second….and it’s close to 1.618. Same with your leg to body ratio, hand to elbow, finger to hand….

And then you get to facial features….rather than try to define it for you, go here.

But, whilst general beauty can be ‘created’ using phi, that doesn’t mean that phi is beauty. This is one of the areas that I think maths will never be able to completely explain: that of likes, dislikes, loves, hates, appreciation, ridicule. Whilst we can find (with relative ease) links between things that people like, and therefore create something generic that appeals to most people, we can never find something that anyone will truly find breathtaking. I am a huge fan of the TV series Numb3rs, and on one of the episodes they are dealing with music, and Charlie ‘explains’ that there are some sequences of notes and tones that appeal to everyone, and, using this, we can analyse music and find, with relative accuracy, how well a certain song will do when it’s released. I don’t know how accurate this is, but I do know that we can not quantify something as individual taste. Whilst maths can certainly be used to give us an idea of how people will react to something, we can’t guarantee it’s success. That being said, I do recall a quote that went something like “given all the information, we can predict anything”….