The Hourglass

Not the flowing waters of time but the falling sands of time have given modern poets their favorite metaphor for the passing hours. In England, sandglasses were frequently placed in coffins as a symbol that life's time had run out. "The sands of time are sinking," went the hymn. "The dawn of heaven breaks." But the hourglass, measuring time by dripping sand, comes late in our story. Sand was, of course, less fluid than water, and hence less adapted to the subtle calibration required by the v...

 Spring Recapitulates Evolution

Spring provides a kind of annual recapitulation of the evolution of life on Earth, an opportunity to celebrate anew the greening of the planet three and a half billion years ago by the first photosynthesizing bacteria. All life—the whole glorious parade along the path—depends upon the photosynthesizers. As spring dresses the deciduous woodlands in its Easter best, the nonphotosynthesizers get moving too. Suddenly the woods are skittering, fluttering, munching. singing. From rock-hard seed...