The existence of life places strong constraints on the cosmological initial conditions and the laws of physics. Cosmologists have long been intrigued by the "unreasonable" bio-friendliness of the universe in this regard. The explanation of choice is now the so-called multiverse cosmological model, which emerges naturally by combining the inflationary universe scenario with string theory. However, in the absence of an efficient panspermia mechanism, the question of whether or not life is widespread in the universe is not addressed by cosmology. Rather, it hinges on whether biogenesis is dominated by chance, or some elusive "life principle". One way to test the fashionable, but as-yet unjustified, claim that life arises readily on earth-like planets is to seek evidence for multiple genesis events on Earth. I offer some proposals for experimental test.
P. C. W. Davies, Proc. SPIE Int. Soc. Opt. Eng. 5906, 59060I (Sep. 22, 2005)
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