OK, we have no way of knowing how many other lifeforms may be out there, how bright they are, or how advanced they’ve become.

Our own, admittedly limited, knowledge and experience shows us that there is probably other life out there, and that some of it at least is likely to be intelligent. Because the Universe we can see is composed of the same types of matter and energy we are familiar with, and that these must be subject to the same laws they appear subject to here. Life is not a statistical anomaly, it is a series of chemical reactions which are wholly dependent on the nature of the atoms and molecules involved. Where they exist in sufficient quantity and proximity, and where the environmental conditions are optimal, those reactions must and will occur. Once life exists, so does evolution, if only because the nature of life is to reproduce and adapt in ways that will increase the chances of successful reproduction. Evolution is the unpredictable part of the system, because the outcome of the process is dependent upon environmental factors, and these may not always favour intelligence as a means of becoming dominant. So not all life-bearing planets may be suitable for the development of intelligent life-forms.

Then there is the possibility -a very real one — that under different environmental conditions, the chemicals that produce life may be different ones from the ones we know. One can talk about silicon-based life, but there is always the possibility of something even more alien. Life we would not recognise as life, and which would not recognise us, either.

Finally, we use search techniques based upon our own technology. But in doing so we forget, or fail to realise, that the technology we have developed is based upon the materials to hand, the gravitic, chemical and magnetic properties of the planet, and our own sensory and physical configuration. An intelligent invertebrate whose sensory hierarchy places smell and touch above sight and hearing, would produce communication technology that works very differently from ours!

So all in all, the idea of finding and interacting with aliens is all very nice, but unless they are depressingly like us, not very likely! For all we know, there are thriving colonies of aliens living here, but we don’t realise they’re alive, and they think the planet is uninhabited!