# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"Maths helps magicians knot," by Phillip Ball. *Nature Science Update,* 11 September 2001.

Andrew Belmonte of Pennsylvania State University and his colleagues have been doing experiments on how knots form. By observing the effects of a mechanical arm that vibrated a chain of beads, they found that knots appeared in the chain only when the motion of the chain was chaotic. The knots formed when the unattached end of the chain passed through temporary loops. Furthermore, the researchers found that the simplest kind of knot---the trefoil---almost never appeared (or if it did appear, it vanished quickly) but more complicated knots did appear. An article about the research was published in the *Physical Review Letters,* vol. 87. (Note that "maths" is the British way of shortening "mathematics.")

*--- Mike Breen*