In Time’s Arrow, Time’s Cycle, Stephen Jay Gould tells the story of one John Playfair, who in 1788 accompanied the great British geologist James Hutton to see an ‘unconformity’ at Siccar Point in Scotland. With the help of this geological visual – an ancient erosion surface dividing two layers of rock, one gently sloping, the other vertically tilted – Hutton explained to Playfair that the Earth is a machine ceaselessly repeating a cycle of erosion, deposition, and uplift. Playfair later wrote: “The impression made will not easily be forgotten … Revolutions still more remote appeared in the distance of this extraordinary perspective. The mind seemed to grow giddy by looking so far into the abyss of time.”