Microlensing Meets SETI:
Observations of Evolutionary Endpoints?

Putative planets are being discovered around nearby stars at the rate of one a month. A subset of these planets and their moons orbit in the liquid water zone around their stars and provide potential foundations for the development of life. While the evolution of intelligent life may be rare, arguing its chances down to one in a billion or lower seems very difficult. Thus we must consider that other technological civilizations may exist in our galaxy. Exponential growth in technology (e.g. Moore's Law), rapidly pushes such civilizations to the limits allowed by physical laws. For our civilization it appears that only 130 years will be required from the discovery of the electron to reach the limits of atomic scale construction (molecular nanotechnology). While we cannot easily predict the developmental path of technological civilizations, we can describe what such civilizations will look like at the limits imposed by physical laws. In order to maximize their intellectual capacities and minimize their long-term hazard function, advanced civilizations are likely to convert their solar systems into nested layers of Dyson shell supercomputers ("Matrioshka Brains"). The construction of a Matrioshka Brain by our civilization seems within our anticipated technological capabilities during this century. Natural selection operating at stellar and galactic scales will eliminate civilizations that fail to follow this path, leading to the conclusion that such objects should come to dominate the population of objects in galaxies. Unexplained observations in astronomy, particularly the missing baryonic dark matter and microlensing, are consistent with the expected characteristics of Matrioshka Brains. It is suggested that astronomy is inherently incomplete unless it includes the natural history of technological civilizations as possible explanations for observed phenomena.