Ray Kurzweil, 65

VIEW OF THE FUTURE: Within 20 years, we will have millions of nanobots inside our bodies that will augment our immune system, enabling a life virtually free of disease. By 2045, we will make—or become—a machine more intelligent than humans, a theory known as the technological singularity. This will enable us to bring back deceased loved ones using their DNA and personal items. Kurzweil plans on reuniting with his dad.

HOW HE'S PREPARING FOR IT: Kurzweil, who sells a line of vitamins and low-fat, low-carb, low-calorie health food with antiaging guru Dr. Terry Grossman, eats a special diet and takes at least 150 supplements a day in the hopes of surviving until the coming age of immortality.

BONA FIDES: Where to start? Director of engineering at Google; holds 19 honorary doctorates; cofounder of the Singularity Summit conference; pioneer of speech-recognition technology (think Siri) and text-to-speech synthesis (think Stephen Hawking's speech-generating devices); inducted into the National Inventor's Hall of Fame; author of five best sellers; and Time magazine cover subject. Also: Predicted the downfall of the Soviet Union, the Internet explosion, and the proliferation of Wi-Fi. Laid down some mad beats with EDM star Steve Aoki on the track "Singularity."

DOOMSDAY SCENARIO: Is dismissive of those who fret about Earth's future. His biggest fear is dying before his master plan takes shape.

HATERS: According to Douglas Hofstadter, Pulitzer Prize–winning author of Göedel, Escher, Bach, "If you read Ray Kurzweil's books . . . what I find is that it's a very bizarre mixture of ideas that are solid and good with ideas that are crazy. It's as if you took a lot of very good food and some dog excrement and blended it all up so that you can't possibly figure out what's good or bad."

• • •

Peter Thiel, 45

VIEW OF THE FUTURE: Thiel believes the world is broken and envisages a planet consisting of self-governing "start-up" communities founded on Ayn Rand–style principles and built on ocean rigs, which will have tens of millions of residents by 2050 and no welfare or minimum wage.

HOW HE'S PREPARING FOR IT: Bolstered by a net worth of $1.6 billion, Thiel invests in the Seasteading Institute, the think tank behind the floating communities, and has given $3.5 million to the Methuselah Foundation, which aims to reverse human aging. Immortality comes with a lot of vacation days: Enter SpaceX, Elon Musk's affordable space-exploration company (the Royal Caribbean of the future), to which Thiel's investment firm Founders Fund gave $20 million.

BONA FIDES: The German-born Stanford grad cofounded PayPal and was an angel investor in Facebook—but don't assume futurists love him just for his money. Thiel can nerd out with the best—he's a former chess master and a Lord of the Rings devotee who named his venture-capital firm Mithril Capital Management after the lightweight chainmail worn by Frodo.

DOOMSDAY SCENARIO: Thanks to government meddling (Thiel largely bankrolled Ron Paul's presidential bid), we're living it now, or at least the beginning stages. As the Founder's Fund manifesto states, "We wanted flying cars, instead we got 140 characters." Chalk it up, says Thiel, to crippling regulations, a de-emphasis on science, a decades-long "tech slowdown," and the out-of-control swelling of the financial sector.

BILLIONAIRES SAY THE DARNDEST THINGS: In a 2009 essay, "The Education of a Libertarian," Thiel wrote, "We are in a deadly race between politics and technology. . . . The fate of our world may depend on the effort of a single person who builds or propagates the machinery of freedom that makes the world safe for capitalism."

• • •

Peter Diamandis, 52

VIEW OF THE FUTURE: Man as "multi-planetary species." Diamandis may be the brains behind the Singularity University, a continuing-education program in which he encourages his "students" (most of them academics, technologists, and entrepreneurs) to pursue ideas that will have a positive impact on at least a billion people, but you won't hear him blathering on about immortality. Diamandis has spent his entire adult life thinking about and creating ways to help mankind transition off planet Earth.

HOW HE'S PREPARING FOR IT: In 1995, he created the XPRIZE Foundation, which "addresses the world's Grand Challenges by creating and managing large-scale, high-profile, incentivized prize competitions that stimulate investment in research and development worth far more than the prize itself." The winners of the first XPRIZE famously created a commercial space vehicle that could launch twice in a two-week period. Subsequent winners have achieved breakthroughs in fuel efficiency, oil-spill clean-up, and sustainable lunar exploration. Last year, Diamandis cofounded Planetary Resources, a company devoted to mining platinum, water, and other minerals from asteroids.

BONA FIDES: Worked at MIT and cofounded the International Space University while on leave from Harvard Medical School. Started a rocket-launch company upon graduation.

DOOMSDAY SCENARIO: Getting left behind on Earth.

• • •

Aubrey de Grey, 50

VIEW OF THE FUTURE: Immortality is within our grasp, says de Grey. The hard-drinking (he believes beer provides energy and creativity) biomedical gerontologist, estimates that 100,000 people die needlessly of old age every day. And as for the obvious population problem that would ensue if we could all live for centuries? De Grey, who has no children, says that as we begin to live longer, humans will be forced to reconsider reproducing.

HOW HE'S PREPARING FOR IT: De Grey insists that if his work is properly funded, then the world's first 1,000-year-old human may already be among us. He says he needs about $1 billion—$100 million a year over the next decade—to complete his research. His SENS Research Foundation is funded by underwriters like Peter Thiel.

SIGNATURE STYLE: Rocks a Father Time beard and 'stache and an outfit—baggy jeans and oversize sweaters—that suggests Appalachian meth chef more than mad scientist.

BONA FIDES: He's a Ph.D. from Cambridge; a fellow at the Gerontological Society of America, the American Aging Association, the Institute for Ethics and Emerging Technologies; adviser to the Singularity University; cofounder of the Methuselah Foundation; editor-in-chief of the academic journal Rejuvenation Research; author of The Mitochondrial Free Radical Theory of Aging (1999) and coauthor of Ending Aging (2007).

DOOMSDAY SCENARIO: Having to install an AmeriGlide Ultra Stair Lift in his home.

HATERS: Half the scientific community. In 2005, Technology Review, a magazine published by MIT that has called de Grey's theories "trollish," offered $20,000 to the scientist who could debunk his theory that old age is a treatable disease. Nobody could. How We Die author Sherwin Nuland has called de Grey a "single-minded zealot."

• • •