The Body: A Guide for Occupants

by Bill Bryson

To help us deal better with this fractional lag, the brain does a truly extraordinary thing: it continuously forecasts what the world will be like one-fifth of a second from now, and that is what it gives us as the present. That means that we never see the world as it is at this very instant, but rather as it will be a fraction of a moment in the future. We spend our whole lives, in other words, living in a world that doesn’t quite exist yet.

It is a strange, non-intuitive fact of existence that photons of light have no colour, sound waves no sound, olfactory molecules no odour. As British doctor and author James Le Fanu has put it, ‘while we have the overwhelming impression that the greenness of the trees and the blueness of the sky are streaming through our eyes as through an open window, yet the particles of light impacting on the retina are colourless, just as the waves of sound impacting on the eardrum are silent and scent molecules have no smell.16 They are all invisible, weightless, subatomic particles of matter travelling through space.’ All the richness of life is created inside your head.