Is there life on other planets?

Can we calculate the odds of life on other planets?

So, letís assume the President read my column last week and proceeds to privatize NASA. What are the chances that some future private space probe will encounter alien life? Can we answer that question scientifically? Or religiously?

Some revealed religions, such as Roman Catholicism, have an ongoing source of revelation - the church - which can speak authoritatively and even infallibly, on questions such as this. However, I am not aware that any Pope has ever expressed an opinion on this topic, let alone pronounced ex-Cathedra.

Other revealed religions believe that revelation has closed. Protestants usually accept that there has been no divine revelation since the Bible and Muslims that there has been none since the Koran. For all the influence within Islam of certain clerics none has the authority of a prophet, for Allah's last and greatest prophet was Mohammed. Neither scripture mentions extra- terrestrial life.

In science absence of evidence is not usually taken as evidence of absence, unless you have looked exhaustively in all the places that you would expect to find evidence. For the follower of a revealed religion, divinely inspired scripture IS where you would expect to find evidence. So the lack of any mention in the Bible, the Koran or - as far as I am aware - any other significant religious text, of life on other planets might be interpreted as indicative, though not absolute, evidence that there is none. Why would God not mention it if it were there?

For a scientist or a skeptic, evidence is required to resolve the matter either way. We have not looked closely at any planets outside this solar system. Indeed we have only recently been able to authoritatively DETECT planets outside this solar system. And most of those that we have detected are not at all like Earth. One like Earth is too small for us to find.

We have examined Mars, and found no indications that intelligent life has ever existed there. But we have not been able to look in real detail. Given what we know now, it would be surprising to find life on Mars. It would be fairly surprising to find it anywhere in this solar system. But we have not proved its absence.

Beyond this solar system, we honestly don't know.

Some people have tried to calculate the odds of life existing elsewhere, but it depends on your assumptions. Some have calculated that it is very likely others that it is virtually impossible. We canít use the variables in the so-called Drake equation (look it up, I donít have room to explain) to calculate the chances of life occurring, because we would first need to know how common life is, to calculate the variables.

The fact is we have no idea how many planets there are in the Galaxy; whether a planet is necessary to sustain life; what other factors may be necessary; or what caused life on Earth.

You can't reason from one example.

So, depending on your own philosophical bent, the answer is either: a) ask the Pope; b) probably not or c) no idea.

Copyright (C) Quentin Langley 22 July 2005

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