We most easily intuit the passage of time measured in days, months and years, the units with which we routinely calibrate our lives. But the span of the cosmos is incomprehensibly greater. The “Cosmic Calendar” is a useful way of thinking about time. It imagines the span of the universe’s existence as though it lasted a single year. The Big Bang, with which the universe began about 13.6 billion years ago, happens on January 1. The cosmic calendar year ends on December 31, at midnight, coinciding with our current time.
When compressed into a single year, all human endeavour is confined to the last few seconds before midnight on December 31. Indeed, modern humans appear just eight minutes before midnight and the Indus Valley civilisation just 12 seconds before that day ends. In the river of time, humanity leaves the barest ripple.
Despite its evanescence on a cosmic scale, the human race now has the power to irreversibly alter the course of life on earth. The impact of human activity on the planet’s climate is clear enough that one cannot think of the future of the biosphere without accounting for it. Humanity now determines the trajectory of planetary life and the speed at which it changes. Our present, the Anthropocene or Human Age, is a fusion of historical and geological eras, when our species dominates all others.
