To discover that we are not alone in the universe, that there actually are extraterrestrial intelligences out there would fundamentally alter how the human race sees itself, but the much more unlikely event of realising that we are totally alone in the universe would I think have far more more profound implications for our philosophy and our civilisation.
An irrational belief in visits by alien space craft and alien abductions along with a constant stream of films and books involving extraterrestrials suggests that most people want to believe and even find some comfort in the idea of there being other intelligent life in the universe, even if it is green and hostile. My guess is that any survey that looked at this would show that most people believe intelligent life to be a part of the universe.
The starting point for almost any discussion about extraterrestrial intelligence starts with this statement. ‘There are billions of stars in our galaxy and there are countless billions of galaxies, there must be millions of stars with planetary systems that have Earth like planets in them. Therefore, we cannot be alone’. But this argument does not really hold up, the conditions and sequences of events for a world like ours to exist are multiple and complex, a fruit machine with a hundred reels would have to come up with all cherries several times in succession to create it. Ice formation in our atmosphere is infinitely less complex than planetary formation and produces trillions of snowflakes in a blizzard, yet no two are alike.
The universe is thought to have existed for approx 15 billion years. It took the first few billion to create the material i.e. heavy elements, for solar systems like ours to form, but that still leaves many billions of years for intelligent life to have evolved. Accepting that the window an evolving civilisation might have for transmitting radio waves that could reach us is small, (we ourselves are already transmitting much less than 50 years ago (cable /internet /satellites directing their transmissions back at the Earth) one would still expect us to have picked up something, CETI has been operating for 50 years and so far has picked up sweet FA. This alone makes the likelihood of extraterrestrial intelligence slim.
The astronauts who went to the moon were all effected by the overwhelming realisation that the tiny blue globe hanging in the vast emptiness that surrounded them was tiny, fragile, and very alone. We should have no need of evangelical politico/ science to make us care for the future. All we need is to see ourselves and the wonder of life around us as a miracle and place a value on it commensurate with that. A more real sense of the immensity of the universe and an understanding of just how miraculous life is might help us to put a proper value on it. Realising that it may be the only life there is might make us treasure it.
And just to humour me, imagine you have watched the news and there was a report that in conjunction with all the worlds largest radio telescope arrays and the most powerful computer ever built, SETI had analyzed the spectra of every star in the galaxy to identify chemical signatures that would indicate there were civilizations on planets going round them, but had found nothing.
Think about how you would feel.