Issue 50

March 2009
This is the 50th issue of Plus and to celebrate, we've made it especially big. We explore the incredibly life-like images generated by computers and fragile medieval frescoes, find chaos in fluid flows and prime numbers in a sieve, meet the "English Galileo" and a man who's into geeky pop, and learn about the dangers of bacon sandwiches. Plus the usual regular features including book reviews, puzzle and podcasts.
In 1979 decorating work in a house in Vienna revealed a set of medieval frescoes depicting a cycle of songs by a 13th century poet, who was particularly fond of satirising the erotic relationships between knights and peasant maidens. The frescoes are of great historical significance, but they are badly damaged. In this article Carola Schönlieb explores how mathematicians use the heat equation to fill in the gaps.
The prime numbers are the atoms amongst the integers, and while we know that there are infinitely many of them, there's no general formula that generates them all. Julian Havil looks at a little-known algorithm that sieves out all primes up to a given number, and which is astonishing in its simplicity.
Describing the motion of fluids is a huge and unsolved mathematical problem. There are equations that seem to describe it well, but their complete solution is way beyond reach. But could there be a simpler method? The physicist Jerry Gollub tells Plus about a new discovery which combines experiment with sophisticated maths.
As an electronic musician Oli Freke has always been fascinated by sine waves, so much so that he's created a song based on them for the Geekpop festival, which is currently taking place on the Web. In this article he explores his song, touching on ancient Greek mythology, strange piano tunings and Johann Sebastian Bach.
It's International Year of Astronomy and all eyes are on Galileo Galilei, whose astronomical observations 400 years ago revolutionised our understanding of the Universe. But few people know that Galileo wasn't the first to build a telescope and turn it on the stars. That honour falls to a little-known mathematician called Thomas Harriot, who excelled in many other ways too. Anna Faherty takes us on a tour of his work.
The computer animation used in movies and games is now so lifelike, it is very hard to believe that you are actually watching a surface built from simple shapes of triangles. Phil Dench tells Plus how he uses mathematics to help bring these models to life.
Why length matters
These are busy times for Plus. Apart from celebrating our 50th issue by putting together a bumper collection of in-depth articles, news and reviews, we're also working on various special projects, some of which have already gone live, and some of which will reach you over the next few weeks and months. Here's a sneak preview of what's in store for 2009...

Would you prefer a game with a 90% chance of winning, or one with a 10% chance of losing? You might scratch your head and say it's the same thing, and you'd be right, but research has shown that people's perception of risk is surprisingly vulnerable to the way it's presented. In this article David Spiegelhalter and Mike Pearson explore how risk can be spun and there's an interactive animation for you to have a go yourself.

If you're worried that a mathematics degree might limit your career options, then there couldn't be a better person to talk to than Steve Hewson. Find out how his varied career has taken him from the lofty heights of theoretical physics, via the trading floor of a major investment bank, into the maths classroom, and has also seen him writing his very own maths book.
From the geometry of Euclid to the shape of the Universe — geometry is a vast field. We've got plenty of articles exploring geometry from all angles, so have a look and take your pick.
Russian roulette
When Number story first landed on my desk I was struck by its prettiness. With its tasteful and slightly old-fashioned cover design, the unusually compact format for a hardback, and the unassuming title, this book clearly isn't desperate for attention. So I was intrigued to find out whether this quiet confidence is justified by its content, and I'm glad to report that it is.
The Magic Numbers of the Professor revolves around a fictional professor and a huge range of magical numbers. Written in a narrative style, the book documents a series of visits the Professor makes from America to Ireland to visit Owen O'Shea, the author of both this book and a fictional column within the story.
It's not often I get misty-eyed reading a book about mathematics, but that was just what happened when I read this, and several other poems, in the poetry collection Strange Attractors: Poems of love and mathematics.