So the Sci Fi writers have to look further afield, and as we learn increasingly more about our universe the scale of the problem in logistical and plausibility terms becomes harder and easier in equal amounts. For example, a couple of decades ago there was no hard evidence of exoplanets - planets from outside of our solar system - although it was hypothesised that there were potentially millions upon millions of them, with the statistical assumption that some would be life supportable in the same way as Earth. That is, they sat in the Goldilocks orbit around their relative star where the temperature was warm enough to support life without boiling away the water - considered an essential ingredient in all life forms - and not too cold to cause the water to turn to permanent ice.
Of course Sci Fi writers aren't put off by logical arguments like assuming water is essential for all life to exist, or that the Goldilocks requirement is binding on all sentient life forms. Possibly it is, but us writers don't like to let apparent facts get in the way of a good story.
Then scientists started to develop ways to detect the presence of planets around stars without actually having to see the physical ball of rock, first by detecting the wobble of a star as the planet circled while exploiting the bending of light properties that Einstein determined. More recently they have been able to detect the slight dimming of a star as a planet passes in front of it relative to us. The upshot of all this is that the estimate of stars in the universe with planets in the Goldilocks orbit keeps on increasing every time anyone bothers to carry out a quick calculation on the back of a convenient envelope.
All this does for Sci Fi writers is give us more scope from an already rich palette.
The scientists have been upwardly adjusting the estimates even more rapidly of late, largely thanks to the dedicated services of the Hubble telescope which has been discovering planets like there's no tomorrow. And the search for life supportable planets has had a boost as more and more are found to be in the Goldilocks orbit. However until very recently it was believed that exoplanets capable of supporting life were a very long way away. Of course, Sci Fi writers have traditionally handled problems that are technically insurmountable at present - we ignore them.
Consequently in 'The Journeymen' I needed a planet that was close enough to enable space travel by sentient beings across three generations by hitching a lift on a comet that was on a racetrack circuit between earth and their home planet. After a bit of soul searching (and experiments involving a recently licked finger raised in the air) I plumped for a distance of nine light years which, although a challenging distance in today's terms, is just about imaginable as do-able in the near future. Although that isn't a relevant point in the book as the journey I'm talking about happened a little while ago, not in the undefined future. The point is that at the time an exoplanet within nine light years was outrageous given the knowledge of the time (2004) when I wrote the novel.
However scientists have continued to push back the knowledge barriers and have realised that red dwarf stars, stars that burn cooler than our sun and are extremely populous in our galaxy, are actually highly likely to have planets in the Goldilocks orbit - albeit physically closer to the star than Earth is to the Sun. It is estimated that there are about 4.5 billion such stars in our galaxy and around half of them could host life supporting planets. The closest one that would appear to have such a potential planet is 13 light years away, which is pretty ball park in Sci Fi terms. And they're still looking; 4.5 billion stars takes a lot of analysis.
Much of what is written in Sci Fi turns out to be hopelessly wrong in the long run, yet a surprising amount does turn out to be quite close to the truth also - it's a brave person who predicts which ideas will be way off beam and which ones will change the world. It's a smart person who does those things correctly and consistently! I'm not suggesting that because I plumped for a distance that is almost certainly going to end up being correct for a potentially life supporting exoplanet that the rest of 'The Journeymen' will prove to be correct. I'm not even suggesting that the comet ISON, soon to be seen swinging its way around the sun this coming November is more justification - for one thing, it probably originates from within our solar system so that wouldn't make sense.
But if and when you read 'The Journeymen' you may start to wonder if the assertion that there are reasons why the best man doesn't always get the job or the promotion, why the hierarchy in all cultures seems to exist to preserve the status quo and why governments insist on embarking on ventures that don't seem to make sense to normal people is explainable by a quest to push this planet on a technological journey at the cost of the planet could, just, be close to the truth.
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