Are we Alone In The Universe?

But I'm enthusiastic about these searches, because of the import of any manifestly artificial signal. Even if we couldn't make much sense of it, we'd have learnt that 'intelligence' wasn't unique and had emerged elsewhere. Our cosmos would seem far more interesting; we would look at a distant star with renewed interest if we knew it was another Sun, shining on a world as intricate and complex as our own.

NASA Galaxies, stars and planets, a cosmic structure we share with any aliens

If we ever established contact with aliens, what could we discuss with them? I've argued in a new book that we're assured one common interest. We'd belong to the same universe of stars and planets, all made of similar atoms and governed by universal laws. We'd all trace our origins back to a single 'genesis event' -- the so-called 'big bang', which happened about 12 billion years ago.

To firm up the odds on alien life, we need to understand how life begins and evolves. An extraordinary precession of species (almost all now extinct) have swum, crawled and flown during the Earth’s 4.5 billion year history. For a billion years, primitive 'bugs' exhaled oxygen, transforming the young Earth's poisonous atmosphere and clearing the way for our eventual emergence. We know from fossils that a cornucopia of swimming and creeping things evolved during the Cambrian era 550 million years ago. The next 200 million years saw the greening of the land, offering a habitat for exotic creatures ---dragonflies as big as seagulls, millipedes a yard long, giant scorpions and squid-like sea-monsters. Then came the dinosaurs. Their sudden demise opened the way to mammals -- to the evolution of apes and us. We are the outcome of time and chance: if evolution was 're-run', there would be no humans, and we can't predict whether any other species would achieve our dominant role. So we can't lay firm odds on whether 'intelligence' would emerge on another Earth-like planet.