Neal Stephenson -Seveneves torrent

What would happen if the world were ending?A catastrophic event renders the earth a ticking time bomb. In a feverish race against the inevitable, nations around the globe band together to devise an ambitious plan to ensure the survival of humanity far beyond our atmosphere, in outer space.
But the complexities and unpredictability of human nature coupled with unforeseen challenges and dangers threaten the intrepid pioneers, until only a handful of survivors remain . . .
Five thousand years later, their progeny—seven distinct races now three billion strong—embark on yet another audacious journey into the unknown . . . to an alien world utterly transformed by cataclysm and time: Earth