The fact that interactions and bonds play an essential role in physical phenomena can hardly be disputed. Their role in the social world is no less important. The parallel between these two classes of phenomena can be illustrated by two key episodes: the formation of stars and the emergence of agrarian-based societies.

• In the early universe there were molecular clouds composed of low density hydrogen and helium gas. According to current conceptions of star formation, regions where density was high enough (as a result of random fluctuations) became gravitationally unstable and began to collapse. The gravitational collapse released a lot of heat and energy in the same way as a stretched spring releases its potential energy as it resumes its equilibrium length. Part of the energy was radiated but the remainder increased the temperature of the core until fusion ignition occurred. This marked the birth of a new star. If its mass was greater than five solar masses it had a fairly short life time. After several million years its core began to contract and as it shrank it grew hotter; this triggered a new series of nuclear reactions leading to the formation of heavier elements up to iron. Eventually, through a mechanism which is not yet clearly understood, the star exploded. It is known that elements heavier than iron were formed during this supernova explosion. Through its disintegration, all elements contained in the star were released into space to serve as raw material for new stars, planets and living creatures.

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