Chichester, W. Sussex, UK, June 1979
The other day I caught the end of one of those Horizon documentary type BBC programmes where they were talking about time and space and a thing reproduced below called Drake's Formula.
The variables in the formula relate to such things as the number of new stars born each year, the percentage of these that have planets, the percentage of the planets that have conditions conducive to life as we understand it (water, light etc), the proportion that actually develop life, and in turn how much of that life becomes "intelligent" - intelligence (a debatable concept in itself) in this context meaning the ability, and will, to send communications signals across space (in the form of radio waves).
Not surprisingly the variables are subject to plenty of conjecture and a wide range of figures can lead to huge variations in the "answer", from zero to thousands, meaning the formula has been used more to encourage debate rather than provide a true estimate. We, of course, don't really know... yet.
But would it really be possible that there would be no other intelligent life out there when you consider the vastness of the universe - 92 billion light years across at the last count and still growing (consider our own star, the Sun, is only 8 light minutes away and our own galaxy contains 100 billion stars). And this is just our "local" area, our single galaxy, the Milky Way; there are billions of other galaxies out there too. In all it has been estimated that there are more stars in the sky than grains of sand on earth - just think about that - billions and billions of Suns each likely to have planets. Just by the pure chance of overwhelming numbers there must be other life out there. This is the nature of infinity, or near infinity. It is the same argument that says if you put a monkey in front of a typewriter it will reproduce a Shakespeare play word for word if given long enough.
But there is an intriguing factor that I had not considered before. The L in the formula above stands for the lifetime of civilisations. Not only do the civilisations have to exist, they also have to co-exist at the same time in order to communicate. Studies of historical intelligent civilisations here on Earth have suggested the lifespan of a civilisation can be as low as 300 years (subject to various degrees of reappearance and abilities to learn from past knowledge or mistakes) - a sobering thought as our current civilisation apparently accelerates towards self-destruction.
What do I think? Well by feeding in my own figures through an interactive calculator online http://www.bbc.com/future/story/20120821-how-many-alien-worlds-exist using the best scientific consensus I could find for each variable, and a fairly modest figure for L, I came up with the figure 29 - that's 29 alien civilisations out there apparently. Will we make contact in my lifetime? Probably not - a single lifetime is but a blink in the 14 billion year history of our universe but it will surely come one day.
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