Theoretical physicist Michio Kaku, author of the bestselling 1994 book "Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the Tenth Dimension," is a science writer who's had the great good fortune to be dubbed a “futurist,” an expert on things that haven't happened yet, as evidenced in the titles of his last two books, also robust sellers: 2011's "Physics of the Future" and 2014's "The Future of the Mind." His new book, The Future of Humanity: Terraforming Mars, Interstellar Travel, Immortality, and Our Destiny Beyond Earth, continues this trend. 

In this new book, Kaku actually quotes Mark Twain, who once quipped, “There is something fascinating about science. One gets such wholesale returns on conjecture out of such a trifling investment of fact.” And yet the fundamental premise of "The Future of Humanity" isn't truly conjecture but rather inescapable projection of fact: One kind of doom or other surely awaits humans. Ninety-nine point nine percent of all species that have evolved on this planet have likewise gone extinct, and the tenure on Earth of modern-day Homo sapiens is an eye-blink compared to that of many thousands of those now-vanished species.

The rogue's gallery of possible culprits is large and well known. Earth orbits the sun in what Carl Sagan (quoted often in Kaku's book) referred to as a kind of cosmic shooting gallery, with potentially life-eradicating comets and asteroids whizzing into the inner solar system all the time; a direct impact by virtually any of these Near Earth Objects would probably wipe out most life on the planet. The general climate of Earth is currently lulling between two ice ages, so Kaku is entirely warranted in speculating about how crushing a new ice age would be for a species like humans, which grew and flourished in that warm trough. And there's always the Yellowstone Supervolcano, which is statistically “due” for the kind of eruption that would darken the skies of the planet, render agriculture all but impossible, and imperil all life on Earth.

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