... yet still we await E.T.'s first message.
Sun, 13. November 2011
So Many Stars...
This is a wide angle image (ten degrees) that I took of the Milky Way in the constellation of Crux, the Southern Cross. Reduced to just 500 pixels in width to fit this blog, it looks less impressive than it does > Here < on my astro-website - but every dot is a star, every star cloud consists of many countless stars. So how many other civilisations live on the countless planets that seem likely to be orbiting around many of the stars in this image?
Ask people about the possible existence of aliens and you will probably get only two types of answers. A Type 1 answer is a very strongly held belief that aliens must exist "because of the multitudinous number of stars and planets that exist out there." A Type 2 answer is the belief that alien activity, in the form of "UFOs," already exists here on Earth.
The Type 1 respondees will often irresistably argue that it would be implausible, irrational or possibly even arrogant to imagine that our host galaxy is not teeming with other intelligent civilisations, just like ours. This statistical argument seems attractive. The galaxy is incomprehendibly large and contains at least 200 billion stars, some astronomers say even double that. Who does not find it difficult to comprehend so many stars, and who does not daydream that the tricky circumstances of the evolution of intelligent humans have not been replicated elsewhere in the galaxy. Yet still we await E.T.'s first message.
Some argue that the evidence for alien existence is that humans are here. It's happened here, so it happens everywhere. That argument has no logic and it proves nothing. It's a bit like saying the Universe is awesome, so that proves god created it. No it doesn't.
We stare up at 200 billion stars and argue that, statistically, other civilisations must have evolved on many of them. Yet E.T. remains silent. We rarely stop to consider what an astonishing statistical coincidence it would be if all of the communicable civilisations that ever existed were occurring right now during our own (so far very brief) tenure as a communicable civilisation. Amid the understandable awe at the immense number of stars, it is easy to forget the galaxy's immense age and the evolutionary process it has been through so far. The Universe is 13.7 billion years old and the Milky Way is believed to have formed 13.2 billion years ago. How many communicative civilisations can we imagine have existed since then? A thousand? Perhaps a hundred thousand?
If we took an optimistic view, that a communicative civilisation might, on average, last for 1,000 Earth years before it is destroyed either by it's own technology or a natural disaster, then it would be statistically possible for up to 13.2 million intelligent civilisations to have existed in the galaxy during it's life so far without even one of them overlapping with another! That is a very simplistic and theoretical way of illustrating that we cannot overlook the immensity of time when gazing at the number of stars and dreaming about whether they are currently homes to other civilisations. Despite the huge size of the Milky Way, it is so old that even if a theoretical thirteen million galactic communicable civilisations, each lasting a thousand years, occurred since it's formation, ours could still be the only one which exists at this point in time!
The statistical chance of another civilisation being close to our own current state of technology are very remote, no matter how many other civilisations exist. If they are behind us they won't have radio communications yet. If they are ahead of us, they may have moved on to other inconceivable technologies - or perhaps even lost the ability to communicate completely.
I live in hope that I will read in tomorrow's newspaper that electro-magnetic communication signals from an alien civilisation have at last been detected - but 'hope' is not the same as 'belief'. Unlike many, I am comfortable with saying "I don't know" and being receptive to all possibilities, whatever our perception of the mathematical odds in favour may be. Optimistic entries in the Drake Equation will give answers of maybe hundreds of thousands of galactic civilisation existing right now. Pessimistic entries will produce an answer of only one. That would be us. You could take the middle road and assume several thousand advanced civilisations exist - but even if that is so, they may not be anywhere near our local galactic suburb (which if you assume to be a radius of 500 light years and ignore the thickness, represents less than 1/100 of 1% of the galaxy's "flat" area).
SETI, (the Search for Extra-Terrestrial Intelligence) has been going for over forty years now, yet despite the increased sophistication of our observations, E.T.'s voice hasn't been heard yet. It has to be a point of concern that we have not yet detected any other communicable civilisation within our region of the galaxy.
We must keep looking.