Seven Brief Lessons on Physics

by Carlo Rovelli

The difference between past and future only exists when there is heat. The fundamental phenomenon that distinguishes the future from the past is the fact that heat passes from things that are hotter to things that are colder.

There is not an ‘I’ and ‘the neurons in my brain’. They are the same thing. An individual is a process: complex, tightly integrated. When we say that human behaviour is unpredictable, we are right, because it is too complex to be predicted, especially by ourselves. Our intense sensation of internal liberty, as Spinoza acutely saw, comes from the fact that the ideas and images which we have of ourselves are much cruder and sketchier than the detailed complexity of what is happening within us. We are the source of amazement in our own eyes.

We have a hundred billion neurons in our brains, as many as there are stars in a galaxy, with an even more astronomical number of links and potential combinations through which they can interact. We are not conscious of all of this. ‘We’ are the process formed by this entire intricacy, not just by the little of it of which we are conscious.

We are a species which is naturally moved by curiosity, the only one left of a group of species (the genus Homo) made up of a dozen equally curious species. The other species in the group have already become extinct; some, like the Neanderthals, quite recently, roughly thirty thousand years ago. It is a group of species which evolved in Africa, akin to the hierarchical and quarrelsome chimpanzees – and even more closely akin to the bonobos, the small, peaceful, cheerfully egalitarian and promiscuous type of chimps. A group of species which repeatedly went out of Africa in order to explore new worlds, and went far: as far, eventually, as Patagonia – and as far, eventually, as the moon. It is not against nature to be curious: it is in our nature to be so.

I believe that our species will not last long. It does not seem to be made of the stuff that has allowed the turtle, for example, to continue to exist more or less unchanged for hundreds of millions of years; for hundreds of times longer, that is, than we have even been in existence. We belong to a short-lived genus of species. All of our cousins are already extinct. What’s more, we do damage. The brutal climate and environmental changes which we have triggered are unlikely to spare us. For the Earth they may turn out to be a small irrelevant blip, but I do not think that we will outlast them unscathed – especially since public and political opinion prefers to ignore the dangers which we are running, hiding our heads in the sand. We are perhaps the only species on Earth to be conscious of the inevitability of our individual mortality. I fear that soon we shall also have to become the only species that will knowingly watch the coming of its own collective demise, or at least the demise of its civilization.