# ‘All that glitters is not golden’: a Fibonacci Day Roundup

Yesterday was 23/11, also known in some parts as 11/23, and you may recognise this as being a date made of the first four Fibonacci numbers. (Such numerical date-based Fibonacci coincidences haven’t been as exciting since 5/8/13, but at least this is one we can celebrate annually.) This meant that mathematicians everywhere got excited about #FibonacciDay, and spent the day talking about the amazing sequence. Here’s a round-up of some of the best bits, so you can celebrate Fibonacci day in style.

First, you’ll need to educate yourself. There are some fab videos on the topic – here’s one by Art Benjamin, and the first in a series of three by Vi Hart. There’s also an article in Plus Magazine, by Ron Knott.

If you prefer a less serious angle, you could try this FoxTrot comic strip on the subject, or keep an eye out for Fibonacci pigeons (here presented with some satisfyingly rigorous analysis).

To celebrate Fibonacci Day properly, you’ll need to decorate the place – you could get this Fibonacci lamp, in the shape of a Golden Spiral, or go more serious and build Fibonacci numbers into the structure of your building. Or, like MIT, go for some funky wall art:

For a delicious Fibonacci Day snack, why not make Golden Ratio Battenberg cake (see above)? And to wash it down, perhaps some of Andrea Hawksley’s Fibonacci Lemonade (link currently down, but a description and photo are here), with ingredients in the appropriate proportions? While you eat, talk about things attributed to Leonardo De Fibonacci other than the ubiquitous numbers. Here’s a suggestion from Evelyn Lamb:

You can read more about the man himself in this piece about Keith Devlin’s book, The Man of Numbers: Fibonacci’s Arithmetic Revolution. Or you can get the book.

People also made sure they spent the correct proportion of the day pointing out that not everything you hear about the Golden Ratio is true – internet maths person, Vi Hart, got animated about it (attracting at least one hilarious response):

If you too are extremely bored with Fibonacci/Golden Ratio things illustrated with photos of an unrelated shell, Patrick Honner recommends a video by George Hart, in which he explains what a nautilus shell would look like if it were really a golden spiral – and of course, he’s 3D-printed one.

Also, don’t get me started on people who think that A4 paper is in the Golden Ratio – recent TV gaffes on this have included Tom Dyckhoff, in his documentary The Secret Life of Buildings, and on BBC nerd quiz Only Connect a few weeks ago. Here’s another nice blog post, about the Golden Ratio jumping the shark.

A longish post by Donald E. Simanek rounds up some of the ways in which the Golden Ratio is cool, and some others in which people say it is but it’s actually not. Meanwhile, Edmund Harriss recommends an old MAA piece by Prof. Keith Devlin, on Golden Ratio myths.