What is the probability of life developing spontaneously from inanimate matter? I don’t know and neither does anybody else. Nor is any calculation remotely possible without knowing the conditions which cause life to emerge. As Astronomer Royal Martin Rees puts it in Just Six Numbers: “We still don’t know how or where life got started. A torpid volcano is now more favoured than Darwin’s ‘warm little pond’.”
So, if you are a scientist and you don’t know, what to do? Well, why not take poetic licence? The answer lies in the stars; not in themselves, dear Brutus, but in their number (to flagrantly hijack and mangle The Bard’s words).
According to US planetary scientist Dr Sara Seager: “Life beyond the Earth seems ‘inevitable’, given the immensity of the universe…Our own galaxy has 100 billion stars and our universe has upwards of 100 billion galaxies – making the chance for life elsewhere seem inevitable based on sheer probability.” She is by no means alone in her thinking, hence those extremely optimistic scientists sending out radio signals in anticipation of reciprocation.
Clearly these scientists anticipate the possibility of finding something other than plant-life or jellyfish or roaming ruminants or Neanderthals, none of which would make head not tail of a radio signal. If perchance contact is made with a radio-literate species, let’s hope they live close by in our vast galaxy — and therefore a reasonable number of light years away — otherwise the dialogue will be severely stunted.
The nearest star in our galaxy (other than the Sun) is 4.3 light years away, but most are many thousands of light years distant. And what, may I ask, is the conceivable relevance of all those other galaxies? The nearest is Canis Major Dwarf, and that is 25,000 light years’ away. So a message sent today to any intelligent beings living within that galaxy will take at least 50,000 years before the return greeting appears. “Hello, Earthling. When you receive this my civilisation (and I) will be long dead and gone as no doubt will be yours (and you).”
I don’t know whether life exists elsewhere. I am agnostic on the matter. I just don’t like the appeal to a large number of planets (almost all of which are irrelevant to any feasible inquiry because they’re too far away) and to an unknown probability. To me, it sounds like a leap out of science into longing; and a longing destined to be unrequited, yet ever held up as being on the horizon.
Large numbers alone simply don’t do it for me. Personally, I seriously doubt that an ape on a typewriter would ever reproduce Hamlet, no matter how many goes you allowed it.
Of course, not being able to find something doesn’t mean that it doesn’t exist. Suppose that each star has on average, say, five orbiting planets. Then one hundred billion galaxies times one hundred billion stars times five makes 50 trillion, which is indeed a large number of planets. But does this make extraterrestrial life ‘inevitable’?
If God established the conditions for life on the earth alone then it doesn’t matter how many trillion planets there are. No life will be found. Probability theory has no application at all. Sheer numbers don’t matter.
If, however, life on earth was a cosmic accident then it is possible that life could exist elsewhere or has existed and been “extincted” (as Bob Brown put it) or is in process of being generated as we speak, as it were. But, whether it is probable or not depends upon the odds of life emerging, and as this is not known it is simply impossible to reach any conclusion. And it seems particularly invalid to say that it is ‘inevitable’. How can it possibly be inevitable if we don’t know the odds?
Apparently conditions on Earth a few billion years’ ago led to life emerging. From this understanding a conclusion is reached that life must surely exist elsewhere by invoking the plausible power of large numbers. There are so many planets, ipso facto; some are bound to be earth-like and therefore potentially life-producing. Call me unscientific, if you like, but my response is that even with 50 trillion attempts, or 100 trillion — you name it — Hamlet would remain elusive no matter how clever the ape.