Multiscale Hierarchical Processes
Traumen wir uns fur einen Moment in einen zukunftigen Zustand der Naturwissenschaft, in dem die Biologie ebenso vollstandig mit Physik und Chemie verschmolzen sein wird, wie in der heutigen Quantenmechanik Physik und Chemie miteinander verschmolzen sind. Glaubst du, dass die Naturgesetze in dieser gesamten Wissenschaft dann einfach die Gesetze der Quantenmechanik sein werden, denen man noch biologische Begriffe zugeordnet hat, so wie man den Gesetzen der Newtonschen Mechanik noch statistische Begriffe wie Temperatur und Entropie zuordnen kann; oder meinst du, in dieser einheitlichen Naturwissenschaft gelten dann umfassendere Naturgesetze, von denen aus die Quantenmechanik nur als ein spezieller Grenzfall erscheint, so wie die Newtonsche Mechanik als Grenzfall der Quantenmechanik betrachtet werden kann ?
Werner Heisenberg (1901-1976), Deutscher Physiker (Heisenberg, 1986)
Multiscale hierarchical processes are understood as information transduction in networks which are hierarchically structured. The most simple assumption might be a house which is structured into rooms, rooms are structured into furnishings but also people that move from one room to another. Of course cupboards and chairs, computers and TVs as well as human beings are hierarchically structured in a somehow comparable way. We would call our house a hierarchically structured system. If information flows from one room to another - and everyone would agree that this is the case when people live in that house and move objects or direct information - we can speak about hierarchical processes. These processes might comprise the information conveyed by the parents that the food is prepared which leads to a movement of the children towards the kitchen and the covering of the table by dishes, not to mention all the processes that are correlated with eating and enjoying the wonderful meal.
If we agree that the type of hierarchical structure might additionally vary if elucidated from different aspects we speak about multiscale hierarchical processes. Such different aspects can be aspects of spatial organization as it is the case in our example, the house. But in addition also other, for example temporal, organization principles are possible. To summarize all these organization principles we generalize the hierarchical systems to multiscale hierarchical systems housing the dynamics of multiscale hierarchical processes.
Living systems are always spatially hierarchically organized: in this case molecules are the basic entities that form genes and proteins as an intermediate structure on a mesoscale. The proteins aggregate in a quaternary structure to form higher ordered systems that do not necessarily need to be stable in time. The network of interacting proteins is in its turn forming a metastructure that can be understood as a network formed from single proteins. However, also on the temporal scale multiscale hierarchical processes arise. For example, a reaction scheme may represent the dynamics of the chemical reaction of two compounds on the temporal microscale. However, if a certain threshold of concentration of its output is present, another chemical reaction may start and is therefore triggered by the first reaction scheme. Long-term effects like the active movement of our extremities, circadian rhythms, the growth of an organism and senescence are typical examples of processes that change their appearance over time and are therefore a hierarchical metastructure that arises on the network of microscale processes.