How nature connects the dots

Jonny Wise muses on the parallel networks in life

In an ever-growing and modernising society, connectivity becomes more and more important. Not only do we rely on it as individuals but also entire infrastructures depend on it. We live our lives - often without realising it - through interactions with a multitude of both natural and artificial networks. From the network comprising our social circles to the complex neural network that makes us conscious; from the circuitry built into our computers to our vascular circulatory system; and from the veins in the leaf of a tree to the Internet.

In academia, a network is anything represented by a set of nodes and connections. The goal of a network is to transport something between the nodes according to some overriding optimisation, which may be dynamic. For example, when designing a network of roads, the nodes are junctions, and the edges are the connecting roads, while the goal is for vehicles to travel as quickly as possible from one node to any other node in the network. Of course, restrictions arise since vehicles may not occupy the same space, so one has to think about how to reduce flow on popular routes. One may think that the obvious solution is just to build more roads, however this is not always beneficial and may actually result in increased journey time – see Braess’s paradox.

The true significance of network science becomes apparent when its universality is considered. The above example is not particular to traffic; it does not matter whether we consider cars, blood, or even information. Similar sorts of features may be observed to produce certain properties such as flow efficiency, robustness to link loss and energy cost in production. It is often this principle that motivates and justifies the study of very specific and niche networks.

The study of naturally occurring networks in biological systems is of particular interest since they are often the product of millions of years of evolution. These networks are studied since they may be worth mimicking when artificial networks with certain characteristics are desired. For example, physicists at Technische Universität Dresden are investigating the liver as a system of two non-overlapping networks of pipes – one that transports blood to every cell and one that transports bile away from each cell. The networks are classified and compared based on statistics such as average link length, channel width, junction planarity and ‘loopyness’. It’s possible to simulate events such as link impairment due to alcohol and observe how the network re-routes in the most optimal way. Researchers hope that this study will not only lead to better biological understanding of the organ, but also offer motivation for the design of modern supercomputers.

This is just one example of where a very specific area of natural science is being studied with the confidence and expectation that the findings may be far-reaching. The recent explosion in artificial intelligence technologies is another testament to the advancements being made in network science and will unequivocally affect how we interact with machines. Existing within nature we are fortunate to have the universe as a playground for scientific analysis and, ultimately, inspiration when building new things.

From Issue 14