Preparing for the Miraculous

110 eleven talksmany are being detected, thanks to the marvellous orbitingtelescopes and other advanced instruments cosmologistshave now at their disposal. Yet, the question is whetherlife will be found on one or some of them. Experts haveopenly expressed their doubts, so for instance Peter Wardand Donald Brownlee in their Rare Earth, Paul Davies inThe Eerie Silence and The Goldilocks Enigma, and GuillermoGonzalez and Jay Richards in The Privileged Planet.“Of all yet known celestial bodies, Earth is unique inboth its physical properties and its proven ability to sustainlife,” write Ward and Brownlee. Our planet has “a highlyfortuitous set of circumstances that could not be expectedto exist commonly on other planets.” Of what kind arethese circumstances? For instance Earth has a Moon whichis the largest of the moons of all other solar planets, largeenough to stabilize Earth’s spin. Earth is protected by Jupiter,which may be called its guardian because, enormous insize, it catches most of the potentially catastrophic debrisheaded for the Earth. Our solar system is located in the galactichabitable zone, so called because most of the MilkyWay and other galaxies is not favourable for life-carryingplanets; moreover, Earth’s orbit itself is located in the habitablezone around the Sun – closer would be too hot for life,farther away would be too cold.A last factor of importance (there are more): our Sundoes not seem to be as common as ordinarily supposed, buton the contrary to be a rarity, “not only within the MilkyWay but also compared to the majority of other galaxies. Itis often said that the Sun is a typical star, but this is entirelyuntrue. The mere fact that 95% of all stars are less massivethan the Sun makes our planetary system quite rare. Besides,approximately two-thirds of solar-type stars in thesolar neighbourhood are members of binary or multiplestar systems.” (Lewis Dartnell: Life in the Universe)