(From a thoughtful member of a list I subscribe to)

Rowland

Recent photographs from the orbiting Hubble Space Telescope using the newly installed Advanced Camera for Surveys (ACS) reveal a myriad of galaxies stretching back into the 13 billion year evolution of the universe. Some would argue that however improbable life as we know it might be, the sheer number of stars with planetary systems would ultimately take care of that improbability. Throw the dice enough times and eventually you come up with six. Have enough suns in the universe and eventually you come up with an Earth or two.

A challenge to the probability of other life-as-we-know-it has come recently from philosopher David Sergeant. In the second part of an article in Sky&Space (available in newsagencies, June/July 2002), Sergeant looks at some of the other reductions in probability. Most stars (91%) are smaller than our sun and have lower abundances of heavy elements. Furthermore, the sun's placement in the galaxy is crucial. Some may have seen that humorous illustration of the galaxy with an arrow pointing to one of the spiral arms saying, "You are here". In fact, the Sun is not located within a spiral arm but between two. Had it been within an arm there would have been two life-threatening risks. The dense stellar and molecular environment may have dislodged more comets from the Oort Cloud sending them onto a collision course with the earth, and the risk of a nearby supernova explosion which may have obliterated life on Earth. Not only that, but the ability of the Sun to stay free of these dangerous arms is dependent upon the particular size of the galaxy and the Sun's place in orbiting around it. Stars often move in and out of the arms because their speed of orbit around the galaxy centre does not match that of the arms. The Sun does not have this problem. Further, the Milky Way Galaxy in which we live is a barred spiral galaxy of moderate condensation. Such galaxies comprise only 3-4% of galaxies in the universe. Non-barred spirals work against life because their metallicity profiles are steep. By the time a star is located in the right metallicity region in other types of galaxies, it has approached the region of violence not conducive to life. Sergeant does not exclude the possibility of microbial life, which has a tenacity to survive in the most extreme of conditions, (as anyone with a cold probably knows!). Rather, he maintains that life as we know it, is rather improbable and unlikely in the universe.

In the last week we have heard the announcement of an extra-solar planet that occupies an orbit around its star of around the same distance as Jupiter from the Sun. Much was made of the fact in news reports that this revealed another planetary system with the protective effects of a Jupiter-like planet. The news release was not entirely honest. The same extra-solar planetary system also had very large planets orbiting close to the star which would have resulted in orbital dynamics nothing like the solar system. In any case, the protective effects of Jupiter, or a Jupiter-like planet, are rather ambivalent. While the gravitational effects of Jupiter have led to the expulsion from the solar system of many minor planetary bodies that pose a threat to Earth, they have also resulted in minor planets from the Main Belt being thrust into a collision course with the Earth.

In the last analysis, what if Earth is the only place in the universe on which we do find intelligent life? Does that make the God question any less ambiguous? Would the uniqueness and improbability of life on earth be evidence for a God who has designed it this, or confirmation that an accident in the universe was well and truly an accident?

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To which another commented:

I'm with Larry Norman: "If there's life on other planets then I'm sure [God]'s been there too, and has died to save their souls...."