Habitability on local, Galactic and cosmological scales
  The aim of this paper is to underline conditions necessary for the emergence
and development of life. They are placed at local planetary scale, at Galactic
scale and within the cosmological evolution, as pointed out by the Anthropic
Cosmological Principle. We will consider the circumstellar habitable zone (CHZ)
for planetary systems and a Galactic Habitable Zone (GHZ) including also a set
of strong cosmological constraints to allow life (cosmological habitability
(COSH)). Some requirements are specific of a single scale and its related
physical phenomena, while others are due to the conspired effects occurring at
more than one scale. The scenario emerging from this analysis is that all the
habitability conditions here detailed must at least be met. Then life asks
something which may appear as "a monstrous sequence of accidents" as Hoyle
(1959) thought, or as providential collaborations leading to realize how finely
tuned is the architecture within which Life, as precious stone, is embedded.
