What does it really mean to say that time ‘passes’? Why does time pass faster in the mountains than it does at sea level? The physicist explains in this extract from his latest book I stop and do nothing. Nothing happens. I am thinking about nothing. I listen to the passing of time. This is time, familiar and intimate. We are taken by it. The rush of seconds, hours, years that hurls us towards life then drags us towards nothingness ... We inhabit time as fish live in water. Our being is being in time. Its solemn music nurtures us,...