The Drake Equation gives an estimate of the number of civilisations in our galaxy which might be able to communicate with us. The problem with it is that most of the terms in the equation are completely unknown, so different interpretations of the idea give wildly different results.
For an SF writer this is both a problem and an opportunity. On the one hand I’m sending my characters out in their “swift ships upon the wine-dark void of space” (all right, I’m misquoting) and I’ve no way of knowing how likely it is that they’ll find intelligent aliens. On the other I can guess at almost all the terms in the Drake Equation with no real fear of being contradicted.
In the thirty years since Jane came bounding into my imagination and took over the timeline there has been a rush of discoveries of exoplanets. This is something I predicted in the first story, and it’s given me the confidence to make a guess at the alien question.
My unjustified personal guess is this:
- Most stars have a planetary system.
- Many planets are at a suitable distance from their star to support life, and have all the chemicals needed.
- On very few of these does life arise.
- Where life does arise it almost always leads to intelligence and civilisation.
My guess is that planets inhabited by intelligent aliens exist, but are very rare, planets which have no life but could be seeded by humans (the process I call terraforming) are quite common. Once the human race gets around to developing faster-than-light spaceship technology we will expand out turning lifeless rocks into living, breathing worlds for a long time before we meet another race. By then I hope we’ll have learned to be polite to our neighbours.