## Plus Blog

December 7, 2014

What's your favourite number? If it's 7 then you're not alone. Alex Bellos, one of our favourite maths authors, conducted a survey this year to find the world's favourite number. After polling more than 30,000 people from around the world, he found that the winner was ... 7!

To find out more about the poll, see favouritenumber.net or read Alex's book Alex through the looking glass. We also highly recommend Alex's adventures in number land.

December 6, 2014

The square root of half the number of a swarm of bees is gone to a shrub of jasmine; and so are eight-ninth of the whole swarm: a female is buzzing to one remaining male that is humming within a lotus flower in which he is confined, having been allured to it by its fragrance at night. Say, lovely woman, the number of bees.

If only all maths questions could be that poetic! We haven't made this one up, rather it comes from the twelfth-century book Lilavati ("The beautiful"), written by the Indian mathematician Bhaskara. According to legend, Bhaskara had a beautiful daughter whose horoscope predicted she was to remain unmarried and childless. Not wanting to do without grandchildren, Bhaskara decided to defy destiny and built a water clock to determine an "auspicious moment" at which his daughter was to get married. But the girl couldn't resist a peak at the clock — a pearl from her dress fell into it and clogged up the hole, so the auspicious moment could never come. To console her, Bhaskara wrote her a maths book (lucky girl!) and named it after her: Lilavati. It's a beautiful book which would make a great present for anyone who likes maths and history.

We came across Lilavati while writing our book Numericon, and it wasn't the only historical marvel we found. Other highlights were John Napier's 1614 book The description of the wonderful canon of logarithms and Claude Shannon's revolutionary 1948 paper A mathematical theory of communication, which laid the foundations for computers as we know them. Happy reading!

December 5, 2014

We can't really remember the last Christmas because this time last year we were very busy writing our book Numericon: A journey through the hidden lives of numbers. The book is a trip through the world of maths via the familiar stepping stones of numbers. If you like what you read on Plus then maybe you would also like Numericon — and thanks to the good people at Quercus, it does look very pretty too!

To get a taste of the kind of stories that are in the book, have a look at these Plus articles:

December 4, 2014

You know the scene… You're all tired and emotional from overindulging at Christmas lunch. It's still two hours til the Doctor Who Christmas special so you decide to play a game to while away the time. How would you like to ensure that you always beat your sister and annoying cousin Geoffrey? Dear readers, we present to you the Grime dice invented by our enigmatic friend James Grime.

These dice are special because although the green die is likely to beat the red die, the red to beat the yellow, the yellow to beat the blue and the blue to beat the purple, the purple die has its chance to shine in the Sun and tends to beat the green! If this sounds confusing, it works in a similar way to the familiar game rock-paper-scissors, or the slightly less well-known rock-paper-scissors-lizard-spock.This is because both games are non-transitive. You can read all about them in James' lovely article or watch his explanation below.

You can find out more about non-transitive games in the Plus articles Winning odds and Let 'em roll.

December 3, 2014

These days that question is easy to answer. If in doubt, pull out your smart phone and check your coordinates. But it's not so long ago that people died for not knowing where they were. Many ships got lost at sea, crashed into rocks or ran aground because sailors couldn't figure out their longitude.

The book Longitude by Dava Sobel tells the fascinating story of that tricky coordinate, why a prize was put on its head and how the puzzle was finally solved by means of a clock. This "true-life thriller" is one of our favourite popular science books ever!

If you've already read the book, or need to pass the time until it turns up under the tree on Christmas day, then read about the maths of navigation on Plus:

December 2, 2014

Have you recently taken up running in a bid to slow the inevitability of middle age? Or are you in the first glorious days of youth, feeling immortal and taking as many risks as you can? Or perhaps you've always taken the safe, and possibly unexciting, path? Whoever you are, you can find out just how dangerous a life you lead in The Norm Chronicles: Stories and numbers about danger by Michael Blastland and David Spiegelhalter.

David, our favourite statistician, has guided us through many a sticky statistical situation and has met many of his own making, including an excellent round on Winter Wipeout. He wrote a column here at Plus and is responsible for the excellent website Understanding Uncertainty, as well as many other activities. Michael, journalist, author and radio producer, is the person who first introduced us to the world of radio and podcasting. He created the fabulous BBC Radio 4 show More or Less.

You can find out more about how risky you are at the interactive website for Norm Chronicles and you can find out more about risk, statistics and probability here on Plus.