Gravity

– It is easy to forget, sometimes, how some of the most ordinary of things in life are also the most remarkable.
– I suppose so. Were you thinking of anything in particular?
– I don't know... Perhaps, if I was forced to give an example, there is the moment in the evolution of our species when our ancestors first stood upright, and indeed walked forward boldly on two legs.
– I do that all the time.
– But that's the point: we now do it all the time. But imagine the thrill of those first faltering steps. We take for granted the complexity of it all: the coordination of muscle and sinew required to haul our flimsy frames up against the crushing force of gravity.
– Is this anything to do with your accident?
– It wasn't really an accident–
– More just tripping over the pavement.
– Well, yes. But it just goes to highlight the immense achievement of being able to walk. And the difficulty of navigating pavements.