Tuesday, March 17, 2009

One of the few bits of knowledge I will remember forever from when I was studying to be a metallurgist* can be summarized** as:

The action is always at the interfaces.
The interfaces, or edges, between two different systems are an extremely important concept when setting up a sustainable agricultural system too. Due to the sudden change in system properties, interfaces are highly active zones, with energy and materials continuously in flux. Life takes advantage of these energy and material exchanges, and thrives far more easily at these discontinuities than in the more homogenous interior of an area. For example, the most biodiverse and productive sites in an ocean are near the shores as well as where cold and warm ocean currents meet. Comparatively, the open ocean is akin to the Sahara desert in terms of biodiversity and productivity.

In permaculture design, increasing the amount of edges is an important tool for maximizing the productivity of a farm. Specifically, ponds are designed with an irregular shape (as opposed to circular) to maximize the water's edge. Wooded and grassland areas are intermingled. Of course, since the biodiversity is high in any area, there are a lot of micro-interfaces where different organisms interact. All of this improves the resource efficiency and productivity of the designed ecosystem.

The corollary is reducing the interface area when you want to minimize material use and energy exchange. For example, spherical structures have the least surface areas for a given volume, and are thus the most energy efficient for heating and cooling***.

The edge effect isn't limited to the physical phenomenon**** - the most innovative scientific research happens in interdisciplinary fields (and of course, at the boundary between knowledge and ignorance). Some of the most interesting art and music and literature happens where two different cultures or ideologies meet.

So here's to the fringes. They make the world more exciting and productive!

* 1998-2002. Feels like lifetimes ago!

** For those who want a fuller explanation: The things we use every day (alloys, composites, etc) are made of different combinations of elements and compounds. In metals and alloys, the functional units of the material are crystallites (or grains). A huge fraction of the properties of the material (strength, ductility, conductivity, thermal properties) is attributable to the microstructure, and specificlly the grain boundaries. These discontinuities in the material are high energy sites, and influence the behavior of the material tremendously. Almost all of the thermal and mechanical treatments affect the properties of materials by increasing or decreasing the size, shape, distribution, and energy of the grain boundaries.

Control over the microstructure and boundaries is also very important for controlling the properties of polymers, ceramics, semiconductors and composites.

*** I also remember reading that ancient human dwellings progressed from round to rectangular as prosperity increased, and reverted to round shapes in times of prolonged scarcity. Can't find any references right now. Anyone?

**** Also read the post Some Thoughts on Edge on the Permaculture Reflections blog.



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