Der Rufer (e106) (webpage)
Summary, in English
NOTE: Der Rufer
Der Rufer, for percussion quartet was written for and dedicated to Olaf Tzschoppe and the Bremer Schlagzeugensemble and is the first result of a planned, long-term collaboration between Lund University/Malmö Academy of Music and the European Spallation Source, a multi-disciplinary research facility based on the world’s most powerful neutron source. ESS will enable scientific breakthroughs in research related to materials, energy, health and the environment, and addressing some of the most important societal challenges of our time. In the first step of this cooperation, I collaborated with John Weisend, Deputy Head of Accelerator Projects at ESS looking at the issues surrounding turbulence in superfluid helium.
The title, Der Rufer refers to a sculpture in Bremen by Gerhard Marcks (1889 – 1981) that refers to a Greek Herald from Homer’s Iliad. On the base of the sculpture is written: Der Rufer is modeled on the figure of the stentor (Herald, bard, or crier) who shouted as loudly as fifty men in a generous and brazen voice (Homer, Iliad, 730 BC).
For some time, I have been interested in the motions of turbulence in fluids and was intrigued to enter into discussions about perhaps one of the greatest discoveries in physics in the first half of the 20th century, that of superfluidity. Superfluid helium (also known as He II) occurs when liquid helium is cooled to within 2.172 degrees of absolute zero (absolute zero is about -273° C). In this ultra-cool region, helium can flow without viscosity or friction, but seldom without turbulence. As I learned through discussions and readings of the literature, superfluidity refers to the flow of a fluid through a tube or pipe with no friction or viscosity. Let’s compare for a second that of normal helium fluid flow that has viscosity and thus friction near the walls of a tube or pipe. An important property for many mechanical systems, including musical instruments, viscosity refers to the measure of the resistance of some element to deformation, or how thick or sticky something is. For example, syrup is higher in viscosity than water. This is how most fluids (including airflow) react in the real world.
But, fluids with zero viscosity are extremely rare. When a fluid is produced with zero viscosity this means the fluid can flow without any loss of kinetic energy. What this means is that if you started water flowing in a small capillary tube the flow will eventually stop since atoms in the liquid will collide with one another and with the tube wall and slow down. But if you did that with superfluid helium and come back 10 years later, the liquid will still be moving.
Superfluid helium features other amazing behaviors, like the ability of a fluid to flow up the side of a wall or to fit into and flow through impossibly small, molecular-wide spaces, or for the body of the fluid to remain steady when a container is spun, or to produce a frictionless fountain that will flow forever. In my composition Der Rufer, I loosely modeled eight principles involved in ultra-cold physics.
- Lärare (Musikhögskolan)
- Collaboration between European Spallation Source (Weisend) and the Malmö Academy of Music (Edgerton)