Sustainability: A Tedious Path to Galactic Colonization

Civilization cannot sustain an exponential growth for long time even when neglecting numerous laws of physics! In this paper, we examine what are fundamental obstacles to long term survival of a civilization and its possibility to colonize the Galaxy. Using the solar system as a reference, resources available for sustained growth are analyzed. Using this information, we will explore the probability of discovering a civilization at its different stage of energy evolution as estimating some possible value of L, the typical life time of an extra-terrestrial civilization.