power is a central phenomenon in societies. So for ages, numerous power perceptions in philosophy and sociology have existed. Measuring power of an actor in its social fabric is a difficult issue, however. After sketching first attempts for this in social network analyses, we develop a new power theory. To this end, we distinguish between vertices in the network and actors acting in vertices. Vertices get structural power potential from their position in the net. in an entropy-driven model such potential can be calculated for all vertices; for selected networks, the method is exemplified. Actors in vertices can deploy power potential once they have respective personal skills, and dominate actors in adjacent vertices. if chosen with suitable care, an alliance of actors can even dominate the whole network. the findings are applied to the famous 9/11-network with 34 vertices and 93 edges. A short survey of power perceptions in history. Power is a central phenomen in societies: Who exerts power on whom, to which degree, using which resources and at which costs. Following Witte 1 even in the animal kingdom we observe manyfold power relations perhaps indicating an evolutionary setting. In occidental cultures, the issue of power was and is omnipresent. Linguistic terms with different etymologic roots like Anweald, Auctoritas, Macht, Maht, Potentia, Potestas, Pouvoir, Power refer to this. According to Platon exertion of power is part of human nature. Aristoteles brings into focus hierarchical dominance structures like slavery, despotism and political sovereignty. Often the consideration of power served as a justification of brute force executed by church or state, e.g. Padua 2 , Ockham 3 , Hobbes 4 , Marx 5 , then broaden this narrow view. So Ockham as well as Marx detect estate/capital as an instrument of power. Witte perceives different power systems 1 • according to their extent (individual, micro, meso, macro), • according to quality (affective, cognitive, conative). This distinction then adds up to different forms of social power: expert power, information power, power by pressure, power by reward. In all aspects presented so far there was little attempt to measure power. Jakob Moreno in 1925 emigrated from Vienna to the US and wrote his pioneering article 6 "Who shall survive: a new approach to the problem of human interrelation". For the first time sociological relations between actors were illustrated by graphs. Further research of sociologists made graphs a successful tool to measure structural characteristics of the social fabric, like centrality, closeness, betweenness, etc. But only in the 1960s did the very question come up of how to measure power. power in social networks. Social Networks (SN) are sets of actors and their manifold relations. Graphs, hypergraphs and multigraphs are modern tools to illustrate such networks. A first introduction we find in the textbooks of Jansen 7 or Scott 8 ; the reader interested in more sophisticated mathematical models might tend to study the compendium of Newman 9. Impor...