from Part V - Exoplanets and Life in the Galaxy
Published online by Cambridge University Press: 05 December 2012
Introduction
In 1929, the observation of the relative motion among galaxies by Hubble was interpreted as evidence of the cosmological principle, according to which no position (galaxy) in the universe is privileged. The discovery in 1964 of the electromagnetic fossil radiation at close to 3 K provided the missing experimental link between the unique thermodynamic origin of the universe and the present observable stellar era. These are the foundations of the standard cosmological model. The thermodynamic origin and the various stages of evolution provide the framework to understand the process of nucleosynthesis, and we expect that the relative abundances of the chemical elements in the universe are uniform on the large scale.
At this point, we might ask whether it makes sense to talk about the formulation of a “bio-cosmological principle,” stating that the probability of finding life in the universe is uniform, with no privilege for our galaxy. But right away we find a difficulty: in the standard cosmological model the observables are well defined by physics. Instead the assumed probability of finding life in the universe refers to something – life – that is not defined rigorously. We do not have a definition of life usable everywhere; we are in a pre-Galilean stage.
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