I remember a maths teacher telling the class —and he sounded confident — that the biggest number that can be meaningfully encompassed by the human brain is one million. That is the total number of little squares on 150 sheets of graph paper — the paper lined with green ink on which most of us learned geometry.
Stand a couple of feet away and you can hold all 150 sheets within your field of vision, but you can also see each of the individual squares. To put it another way, a million is a number we can make visual sense of. Beyond