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Stephen Hawking 60th Birthday Conference

Knots crop up all over the place, from tying a shoelace to molecular structure, but they are also elegant mathematical objects. Colin Adams asks when is a molecule knot a molecule? and what happens if you try to build a knot out of sticks?

This issue's topics

• New maths column
• Gyros lighter while spinning
• Longest number
• Softball teams problem

New maths column

From Dean Browell <browells@earthlink.net>

Just an F.Y.I. that a new section and article with a mathmatic skew has debuted in the online magazine Skewed Perspective.

Topic of the month

• Safe as houses - the difficulty of evaluating risk

Have you anything to say on this or other subjects of interest to Plus readers? E-mail plus@maths.cam.ac.uk.

C. J. Budd and C. J. Sangwin show us how to create mazes, and explain why mazes and networks have much in common. In fact the study of mazes and labyrinths takes us into the dark territory of murder, suicide, adultery, passion, intrigue, religion and conquest...

Building the Cretan Labyrinth

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This issue's topics

• New maths column
• Gyros lighter while spinning
• Longest number
• Softball teams problem

New maths column

From Dean Browell <browells@earthlink.net>

Just an F.Y.I. that a new section and article with a mathmatic skew has debuted in the online magazine Skewed Perspective.

Topic of the month

• Nerdish or nice - how schoolkids see their maths teachers

Have you anything to say on this or other subjects of interest to Plus readers? E-mail plus@maths.cam.ac.uk.

Steven J. Brams uses the Cuban missile crisis to illustrate the Theory of Moves, which is not just an abstract mathematical model but one that mirrors the real-life choices, and underlying thinking, of flesh-and-blood decision makers.

The physical implications of limiting processes

This limiting process, where the slice is shrunk down to arbitrarily small thicknesses, really provokes some deeper questions!

Suppose you put \pounds 1 in a bank. The bank pays 4\% interest a year, and this is credited to your account at the end of a year. A little thought shows that at the end of five years an amount of money equal to \pounds$(1+0.04{)}^5$ will sit in the bank (this bank charges no fees). \par However, if the interest (still at an annual rate of 4\%) was "compounded" every quarter, then the amount at the end of five years would be \pounds$(1+0.04/4{)}^{4\times 5}$.

Suppose you put \pounds 1 in a bank. The bank pays 4\% interest a year, and this is credited to your account at the end of a year. A little thought shows that at the end of five years an amount of money equal to \pounds$(1+0.04{)}^5$ will sit in the bank (this bank charges no fees). \par However, if the interest (still at an annual rate of 4\%) was "compounded" every quarter, then the amount at the end of five years would be \pounds$(1+0.04/4{)}^{4\times 5}$.