Our Sliver of Time

摘要

In which we reflect on three milestones in the maturing of our moist blue planet—the dawn of life, the growth of oxygen, and the first Earthlet spores—stunned by the privilege of being alive during our brief sliver of time. Less than four decades ago, life flew off Earth to visit another celestial body. It was an extraordinary milestone in the maturing of our planet. Indeed, when ranked with other events during the almost five billion years since our planet condensed-out from cosmic debris, I think only two rank its equal. The first occurred nearly four billion years ago when life itself began. Early life required neither sunlight nor oxygen and came to be called anaerobic. Oxygen was a poison to this early life that had grown up in a world without an oxidizing atmosphere.