“The community of thinkers on distant-future questions stretches across disciplinary bounds, with the primary uniting trait a willingness to think about the future as a topic for objective study, rather than a space for idle speculation or science fictional reverie,” says writer Graeme Wood.

They include British Astronomer Royal Martin Rees, theoretical cosmologists like Sean Carroll of the California Institute of Technology, who recently wrote a book about time, nonacademic technology mavens like inventor and theorist Ray Kurzweil, and Nick Bostrom, a philosophy professor who heads Oxford University’s Future of Humanity Institute.

What binds this group together is that they are not, says Bostrom, “just trying to tell an interesting story.” Instead, they aim for precision, systematically analyzing for the first time the worryingly numerous ways in which humanity might fail to survive to see that long future.

The odds of human extinction in the next century: 50 percent (Rees) or 25 percent (Bostrom). “It turns out, if you act and consider all good — including that of future generations — you could outweigh the good you can do today by eliminating world hunger, say, or curing malaria,” says Bostrom. “The reduction of existential risk turns out to be one of the most important things we can do.”

The next hundred years or so might be critical for humanity,” Bostrom says, listing as possible threats the usual apocalyptic litany of nuclear annihilation, man-made or natural viruses and bacteria, or other technological threats, such as microscopic machines, or nanobots, that run amok and kill us all.