It was a long walk today, close to 6 kilometres, and hilly as well, so we became quite tired at the end. The conversation was interesting indeed. I explained to Gianluca the concept of biodegradability. We pondered on the sounds made by animals, in particular, chickens. We realised that while cows moo and cats meow, a dog doesn't woof - it barks. I suggested, without much conviction, that dogs say "Bark, bark!" but Gianluca would have none of it. We never got to work out the word for chickens' utterances.
We argued some more on whether dinosaurs had roamed the particular spot where we were walking, and I insisted that physical locations only appear to be fixed - they are actually in motion but it's so extremely slow that we cannot notice it for hundreds of years. However, going back 65 million years the lie of the land would be completely different, and "this exact spot" doesn't have any meaning that far back in time.
Terribly pedantic, I know.
Mind you, Gianluca was on fire today. Billions and trillions were flying all over the place. He wanted to know whether any human can run faster than a car, whether there's a smaller unit than a millimetre (which led us to conclude that there are a billion micrometres in one kilometre). As we sat down to rest, he asked me about the smallest object in the world. I was treading on shaky ground here. We were in the domain of subatomic particles. Electrons are very small, ventured Gianluca, correctly. I have the impression that electrons are made up of quarks, but any smaller than that I'm lost.
Another difficult question - where's the narrowest passage in the world? You mean, that people can walk through? Yes. Wild guess - Yemen.
Final bombshell - how many ants have been trodden on and squashed by humans since the beginning of time? Here I had to protest that this was totally impossible to calculate. To begin with, going back in evolution, you cannot pinpoint exactly when our ancestors could be called humans and not apes. "Include apes as well," which solves nothing since apes also evolved from something else. But Gianluca insisted, "Close your eyes and imagine you're in a quiz competing with a million others to get the best estimate." I said, "Is there anyone who knows the correct answer?" "Just imagine and give an answer!"
Ok, ok! 15 billion souls times a hundred gave a trillion and a half ants squashed by humans throughout history. Except that, I later realised that 100 ants squashed per lifetime is too conservative - about two ants per person per year. Surely, it has to be more than that.
I'll keep the pictures of today's walk for Gianluca's post, when he comes round to writing it. As I write, he's busy with his buddy Andrew, who came over to visit tonight...