My most vivid encounter with the vastness of nature occurred years ago on the Aegean Sea. My wife and I had chartered a sailboat for a two-week holiday in the Greek islands. After setting out from Piraeus, we headed south and hugged the coast, which we held three or four miles to our port. In the thick summer air, the distant shore appeared as a hazy beige ribbon—not entirely solid, but a reassuring line of reference. With binoculars, we could just make out the glinting of houses, fragments of buildings.

Then we passed the tip of Cape Sounion and…