Spaghetti lubricated in olive oil is shedding light on why knotted ropes or strings used by sailors, anglers and mountaineers snap where and when they do.

"Finding the breakage point on a rope with some degree of accuracy is very difficult. Materials like nylon break so fast that it is impossible to see where or why a break occurs, even with a high velocity camera. Instead, the best material to see a breakage turns out to be well cooked spaghetti," said Dr. Giovanni Dietler of the University of Lausanne in Switzerland.

Mountaineers, sailors and anglers all recognize that knotted ropes break easily near to the site of the knot. By looking at why a rope or string breaks at that site, it is hoped that stronger fabrics can be produced that overcome this problem.

The researchers, based at the University of Lausanne and at Poznan University of Technology in Poland, analyzed consecutive frames of film to see where the breaking process begins. They learned that the breaking point was localized at well-defined points close to the entrance to the knot, where the spaghetti was very bent.

The researchers then carried out computer simulations of tightening knots to see what effect this had.

"It was found that the breakage occurred where the bend in the filament was the greatest," said Professor Piotr Pieranski of Poznan University in Poland.

Knowing that the higher the curvature in the rope, the more chance there is of it breaking can lead to producing materials with new weaving patterns that reduce the curvature. This same principle could also be applied to produce stronger plastics by minimizing the curvature in polymer chains or by avoiding knots within the molecule.

"By comparing localization of breakage points in knotted spaghetti with those reported in molecular simulations of knotted individual polyethylene chains, we were struck by the conservation of the same basic physical principles from macro to nano scale," says Dr. Andrzej Stasiak from the University of Lausanne.

The Institute of Physics is a leading international professional body and learned society with over 30,000 members, which promotes the advancement and dissemination of a knowledge of and education in the science of physics, pure and applied.

It has a worldwide membership and is a major international player in: scientific publishing and electronic dissemination of physics; setting professional standards for physicists and awarding professional qualifications; and promoting physics through scientific conferences, education and science policy advice.

The Institute works in collaboration with national physical societies, plays an important role in transnational societies such as the European Physical Society, and represents British and Irish physicists in international organizations.

In Great Britain and Ireland, the Institute is active in providing support for physicists in all professions and careers, encouraging physics research and its applications, providing support for physics in schools, colleges and universities, influencing government and informing public debate.

(Reference: New Journal of Physics, Vol 3 (2001) electronic-only publication.)

[Contact: Giovanni Dietler, Dr. Andrzej Stasiak, Dianne Stilwell]

14-Jun-2001