One cannot walk down an avenue, converse with a friend, enter a building, browse beneath the sandstone arches of an old arcade without meeting an instrument of time. Time is visible in all places. Clock towers, wristwatches, church bells divide years into months, months into days, days into hours, hours into seconds, each increment of time marching after the other in perfect succession. And beyond any particular clock, a vast scaffold of time, stretching across the universe, lays down the law of time equally for all.