Information theory

Why there is a limit to how much better computer chips can get and what it's got to do with black holes.

Books, brains, computers — information comes in many guises. But what exactly is information?

There's no doubt that information is power, but could it be converted into physical energy you could heat a room with or run a machine on? In the 19th century James Clerk Maxwell invented a hypothetical being — a "demon" — that seemed to be able to do just that. The problem was that the little devil blatantly contravened the laws of physics. What is Maxwell's demon and how was it resolved?

  • What is maths for? - What do we hope people will know after studying maths at school?
  • New Plus posters! - Find out how you can get hold of your own copy of our brilliant new poster!
  • Specially for students - This issue of Plus brings you the first of an occasional series expecially for use in the classroom.
  • Optional maths - should students be able to give up maths at age 14?
  • Outer space - In what will now be a regular feature, mathematician and cosmologist John D. Barrow shares some maths that's amused and intrigued him.
  • Readers' corner- More Strange activities for last issue's Ship of Fools!
  • Information overload - how mathematicians are helping us all to make sense of the vast amount of information now available to us
  • Sum problems - can you be good at mathematics without being good at arithmetic?
  • Readers' corner - Meet Mandy, the cuddly Mandelbrot set!
The mathematics underlying today's complex telephone networks is still based on his work. Erlang was the first person to study the problem of telephone networks.