“Our sun formed 4.5 billion years ago, but it’s got 6 billion more before the fuel runs out,” Sir Martin Rees, the Astronomer Royal, told the audience seated among the busts and weathered books of the institution’s second-story library. “It won’t be humans who witness the sun’s demise: It will be entities as different from us as we are from a bug.”  
 
The occasion for Rees’s mind-bending assertion was his acceptance of the 2011 Templeton Prize, an annual cash award of $1.7 million, payable to individuals who have made “an exceptional contribution to affirming life’s spiritual dimension” — in Rees’s case, by looking millions of years into the future and venturing a guess as to what might be waiting.  
 
Humans have been interested in the future for millennia, mostly as a subject for theologians. But theologians were, along with everyone else, thinking small. Most humans who have ever lived have died in conditions almost exactly like the ones into which they were born, and without written history had no way to grasp that the future might be different at all. Only now have we gained the scientific knowledge necessary to appreciate how exactly how deep a rabbit-hole the future really is: not just long enough to see empires rise and crumble, but long enough to make all human history so far seem like a sneeze of the gods.