Some two billion years ago, the first photosynthetic algae evolved the ability to respond to light—the brilliant Sun by day, the spectral Moon by night. Around 700 million years ago, primitive eye-pits appeared; then, during the Cambrian era, arthropod-like creatures gazed at the sky through true eyes, sensing the lunar rising and setting with their arthropod-like comprehension. So it continued, into the succeeding chapters of life featuring mammals, primates, hominins, and Homo sapiens, the last of them plotting the Moon’s movements and mapping the pockmarked terrain of Earth’s companion.
Then, 50 years ago, the perspective flipped. Apollo 8 took off on a figure-eight pattern around the Moon and, on December 24, 1968, three NASA astronauts peered out at the first Earthrise in the history of life. Most of the reminiscences now popping up across the media focus the Earth itself, seen gibbous and gorgeous from afar. But the true power ...
