Plus Blog

July 8, 2011

Suppose you and a friend have been arrested for a crime and you're being interviewed separately. The police offer each of you the same deal. You can either confess, incriminating your partner, or remain silent. If you confess and your partner doesn't, then you get 2 years in jail (as a reward for talking), while your partner gets 10 years. If you both confess, then you both get 8 years (reduced from 10 years because at least you talked). If you both remain silent, you both get 5 years, as the evidence is only sufficient to convict you of a lesser crime.

What should your strategy be? As a selfish and rational individual, you should talk. If your partner also talks, then your confession gets you 8 years instead of 10. If your partner doesn't talk, then it gets you 2 years instead of 5. Talking is your dominant strategy, it leaves you better off than silence, no matter what your partner does.

The trouble is that your partner, just as selfish and rational as you, will come to the same conclusion. You'll both decide to talk and get 8 years each. Paradoxically, your dominant strategy will leave both of you worse off than silence would have done.

The prisoner's dilemma is one of game theory's most famous games because it illustrates why people might refuse to cooperate when they would be better off doing so. One real-life situation that is similar to the dilemma is an arms race between two countries, in which both countries increase their military might when it would be better for both to disarm.

Read more about the prisoner's dilemma on Plus:

Adam Smith and the invisible hand

Mathematical mysteries: Survival of the nicest

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July 7, 2011

Three cheers for John Barrow, the Director of the Millennium Mathematics Project (of which Plus is a part), for winning the IMA-LMS Christopher Zeeman Medal for his work promoting maths to the wider community!

Barrow has made enormous contributions to the public understanding of mathematics, particularly in his role as Director of the MMP, based at University of Cambridge. The MMP has done a huge amount to develop mathematical interest and ability among school students and the general public with activities such as NRICH and, of course, Plus.

In a joint statement, David Youdan, Executive Director of the Institute of Mathematics and its Applications, and Professor Angus Macintyre, President of the London Mathematical Society, said: "Our two societies have a common priority of promoting mathematics both to school students and to the adult public. Society should not lose sight of the fundamental importance of mathematics, both as a foundation for much of science and engineering, and as a human endeavour aimed at understanding some of the deepest problems about the structure of our universe. Professor Barrow has been at the forefront of mathematics communication for many years and is world famous for his contributions to public understanding of one of the oldest, most beautiful, and most essential of sciences".

The medal is named in honour of Professor Sir Christopher Zeeman, FRS, one of the UK’s foremost mathematicians who spent much of his career at the University of Warwick sharing his love of mathematics with the public. In 1978, Sir Christopher was the first ever mathematician to be asked to deliver the Royal Institution’s Christmas lectures in its 125 year history. Barrow said: "As someone who was inspired by Christopher Zeeman’s compelling presentations of mathematical ideas as a school student, it is a great honour to receive this award that bears his name".

As well as promoting mathematics through his work with the MMP, Barrow is also the author of many books on mathematics and cosmology. His recent publication – One hundred essential things you didn’t know you didn’t know – shows how mathematics explains our world, in a way that is accessible to anyone with only a basic mathematical knowledge. His most recent work, The Book of Universes, shows how mathematics has enabled us to understand so much of the Universe we see around us.

A tireless champion of mathematical awareness for several decades, Barrow has won both the Royal Society’s Faraday Prize and the Kelvin Medal of the Institute of Physics. He has also engaged with the arts and in 2002 his play Infinities premiered in Milan, directed by Luca Ronconi, and won the Premi Ubu Theatre Prize and the Italgas Prize. The Italian edition of his book Cosmic Imagery, about the role of pictures in the history of science and mathematics, won the 2011 Merck-Serono Prize for Science and Literature. Barrow has also been both the Gresham Professor of Astronomy and Gresham Professor of Geometry at Gresham College, London and is a Fellow of the Royal Society.

June 21, 2011

The strawberries are out and it's raining... so it must be Wimbledon time! If you're trying to while away the time waiting for the covers to come off the court then give Cliff Richard a break and take a look at some of the great tennis articles and puzzles here on Plus!


Anyone for tennis (and tennis and tennis...)?
American John Isner and the Frenchman Nicolas Mahut are set for a rematch in the Wimbledon 2011 Championships — but how will it compare with their match of epic proportions from last year? Just how freaky was their titanic fifth set from 2010 and what odds might a bookmaker offer for a repeat?


Making a racket: the science of tennis
A perfect althletic performance takes more than training, it also takes engineers working hard to produce the cutting-edge equipment. If you're a tennis player, your most important piece of equipment is your racket. Over recent decades new materials have made tennis rackets ever bigger, lighter and more powerful. So what kind of science goes into designing new rackets?


Winning at Wimbledon
What does it take to win at Wimbledon? Can you figure out how many games the champion has to win? And how many matches are played overall?

And you can also find out if the robots have their eye on the trophy, if tennis should be in the Olympics and much, much more about maths and sport on Plus and on the MMP's Countdown to the Games.

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June 7, 2011

How big is the Universe? And how small is the smallest thing within it? This cute website developed by Cary Huang puts things into perspective. It lets you explore the entire range of scales, from the smallest length (the Planck length) all the way up to the entire Universe, via atoms, people, giant earthworms, planets, galaxies and more.


June 7, 2011

Kneeling in the mud by a country road on a cold drizzly day, I finally appreciated the wonder that is a lever. I was trying to change a flat tyre and even jumping on the end of the wheel wrench wouldn't budge the wheel nuts. But when the AA arrived they undid them with ease, thanks to a wheel wrench that was three times the size of mine. There you have it ... size really does matter!


Image by CR

A lever is a truly remarkable device that can literally give any of us the strength of ten men. You can counteract 10 men pushing down on one side of a see-saw by applying just 1/10th of their force, as long as you are 10 times further from the see-saw's centre as they are.

This is because the forces acting on a lever are proportional to the distances they are from the fulcrum. In this way a small amount of force moving a longer distance can move a large load over a smaller distance.

Levers are working hard all around us: in see-saws (where the fulcrum is between the loads), in wheel barrows (where the load is between the fulcrum and the force) and even in our very jaws (where the force is applied between the fulcrum and the load).

Archimedes was the first to mathematically describe how levers work and famously said: "Give me a place to stand, and I shall move the earth with a lever." And give me a long enough wheel wrench and I might just be able to change my next flat tyre for myself!

You can read more about levers from Wikipedia, and more about mechanics and about Archimedes on Plus

May 26, 2011
<i>Pegasus</i> made by Robert J. Lang from one uncut square of Korean hanji paper. Image courtesy <a href=''> Robert J. Lang</a>.

Pegasus made by Robert J. Lang from one uncut square of Korean hanji paper. Size: 7 inches. Image courtesy Robert J. Lang.

If you've ever marvelled at the elegance of a paper crane or just struggled to refold a map you will enjoy the next Maths-Art seminar from the London Knowledge Lab.

Applications of Origami will be a practical, hands-on workshop and presentation by Mark Bolitho and members of the British Origami Society. The presentation will cover recent developments in origami and present some of the projects Mark has worked on. It will also review how origami techniques have been adopted in applied design from architecture to product design.

DATE: Thursday 9th June
TIME: 5.00 to 7.30pm
PLACE: London Knowledge Lab, 23-29 Emerald St, London, WC1N 3QS

The Maths-Art seminars are free to attend and everyone welcome. You don't need a reservation but an email to is appreciated for planning purposes. You can also watch past Maths-Art seminars on YouTube and read more about the maths of origami on Plus.

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