On the train this morning, I just finished reading the book
We need to talk about Kelvin by Marcus Chown. It's an excellent book where Chown makes connections between what is readily observable everyday -- the solidness of our bodies and the stuff around us, our reflection on a glass window, the darkness of the night sky, etc. -- to the counter-intuitive realities that quantum physics predict about our universe.
In the last chapter of
Kelvin, Chown lays out an extensive discussion around the probability of us coming into contact with extra-terrestrial (ET) intelligent life. He brings together the views of an array of experts on the subject. Biologists, for one, describe the fine points around how infinitessimally improbable the evolution of complex multi-cellular organisms is, much less intelligent life. To highlight that point, they show how single-cell life forms were around on Earth for more than three billion years before multi-cellular life emerged and flourished only in the last 700 million years. Imagine how lucky a little planet like Earth is. It managed to survive long enough, circling the sun more than three billion times without being blown to bits by a stray asteroid, to see our close ancestors (in relative terms given geological timescales) crawling out of the muck!