Note: This page was written some time in the nineties. I hope to make it obsolete with my new SETI New Zealand website but I'm afraid it's low priority.
Pretty much everyone in our culture with a brain has wondered seriously about this sometime in their life. Why is it so important, and why does it fascinate us so much?
I thinks it's because it's a question which so profoundly affects us - our identity, our self-image, our place in the scheme of things. If we could know once and for all if we were alone or not, it would go such a long way to answering the bigger questions about "the meaning of life".
I've got all sorts of opinions about how the discovery of ETL (extra-terrestrial life) will change our world, but I'll save them for now. Also, this won't be about UFOs. I might try to address that issue at some stage, but for now I'll proceed as if there had never been any UFO sightings. That might seem strange in a discussion on ETL, but this isn't a conspiracy theory argument.
This page is only looking at the question "Is the existence of extra-terrestrial life possible, and if it is, how likely is it?".
Before we begin to look at ETL, I think we have to consider one fundamental question first: What is the Universe doing here anyway? The way I see it, there are two possibilities:
(1) The Universe exists by design, i.e. there is some "Creator"
which put it here.
(2) The Universe exists "by accident", as the result of naturally occurring forces.
How you answer this question will determine the way you approach the issue of ETL. People who believe in a Creator will be asking different questions to those who don't. Let's ask the question from both points of view, in order to cover all possibilities...
...then the question becomes "Did the Creator make life only on Planet Earth?"
This is a little difficult, since it involves trying to work out what God might be up to. Personally, I find deducing God's motives quite a challenge. We're inevitably going to be asking questions which theologians have struggled with for ages, and to which there may be no answers. Here's one such question:
"Why would God make such a huge Universe to house one tiny planet of life?"
Perhaps the Creator envisages a day in which humans will spread to other parts of the Universe, but the laws of physics seem to preclude this. It's almost certain that most of the Universe will remain forever hidden from us. Would God really have made such a vast mass of space completely dead, never to be experienced by any living thing? Or is this just one more puzzle in His/Her/It's plan?
This whole God thing is such a tough one that I'm going to put it aside for the moment. I'll get back to it later.
...then the question is "How likely is it that life has also evolved elsewhere in the universe?"
This is a lot less difficult, since we're dealing with things like physical laws and statistics. Although it's still not possible to use these tools to give us any definitive answers, it's easier than second-guessing God.
Statistics are a good place to start. My "stats 101" is a bit rusty and I intend doing a more technical analysis of this later, but for now I'll just say this...
It's difficult to say what the chances of life evolving accidentally are, since we can only extrapolate from one example (Earth). Obviously it's more than zero, since we're here, so there is at least some chance. We know that life requires certain pre-conditions such as water, but it doesn't seem to need anything that's not found in abundance in space. Mars was probably hospitable to life millions of years ago and we know of numerous other water sources in our solar system.
So let's have a guess at the odds of life evolving in any given solar system. 1 in a million? 1 in a billion? Let's be conservative and say 1 in a million billion. That's pretty long odds, especially if we assume that similar conditions exist in similar solar systems.
We know of at least 100 billion galaxies, each of which might contain several hundred billion stars. Even at these odds, there would be hundreds of millions of planets housing life out there.
Unfortunately I've run out of time again, so that's it for this page so far. If you're genuinely interested, and not just reading this to humour me, then come back later....