The key ideas

The Future of Humanity: Terraforming Mars, Interstellar Travel, Immortality, and Our Destiny Beyond Earth

Michio Kaku, 2018

More than 99.9% of all species that ever lived on Earth have gone extinct. Physicist Michio Kaku believes humanity has a chance to escape their fate by becoming multiplanetary. Step by step he travels from the Moon and Mars to light sails and ideas about transferring consciousness, and each time he asks: does physics forbid this, or is it only a matter of cost for now?

Who it is for

For anyone curious about what really keeps people from living on Mars and flying to the stars: the laws of physics, or money and engineering.

Sooner or later we will have to leave the Earth: either we become a multiplanetary species, or we share the fate of almost every species that has gone extinct.

What the book is about

More than 99.9% of all species that ever lived on Earth eventually went extinct. Michio Kaku opens the book with that number. About 66 million years ago an asteroid ended the age of the dinosaurs. Kaku lists what may be waiting for us: a new ice age, the eruption of a supervolcano such as Yellowstone, a collision with an asteroid and, billions of years from now, an aging Sun. In his words, the laws of physics are clear: sooner or later humanity will face a crisis that threatens its very existence.

Kaku's answer is the term the whole book is built around: a multiplanetary species. A human race with a home on more than one planet.

Almost every chapter follows the same pattern: threat, engineering path, what physics says, how realistic it is. The third step matters most to the author. He keeps separating what the laws of nature forbid from what is simply hard and expensive. Everything said about the future from here on is Kaku's forecast as of the book's release in 2018. And his story begins with a newspaper that declared spaceflight impossible.

Idea 1. The newspaper that apologized 49 years later

In 1920 the American physicist Robert Goddard wrote that a rocket could reach the Moon. The New York Times mocked him in an editorial: in a vacuum a rocket has nothing to push against, and the professor apparently lacked the knowledge taught in high school. The newspaper was wrong. A rocket is pushed by the gases it throws out behind it, and it needs no air to do that.

Goddard kept working. In 1926 he launched the first liquid-fuel rocket, and he died in 1945 without ever being recognized. In July 1969, while Apollo 11 was on its way to the Moon, the newspaper printed a correction and expressed regret for its error.

Even earlier, in Russia, Konstantin Tsiolkovsky, who had been inspired by Jules Verne as a young man, derived the equation of rocket motion. It was Tsiolkovsky who wrote: “A planet is the cradle of mind, but one cannot live in the cradle forever.”

The story is well documented. The lesson drawn from it is Kaku's own view.

The apology appeared on July 17, 1969, three days after Apollo 11 lifted off: rockets do work in a vacuum after all, and the paper regrets the error. Goddard had been dead for twenty-four years.

For Kaku, “impossible” can mean “we don't know how yet”. Before you reject a bold idea, it helps to ask: is it forbidden by physics, or only by today's technology and price?

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About the author

Michio Kaku is an American theoretical physicist, a professor at the City College of New York and one of the founders of string field theory. A well-known popularizer of science, he is the author of Physics of the Impossible, Physics of the Future, Parallel Worlds and other books.

All books by this author: Michio Kaku

Terms from the book

  • Einstein
  • Hawking
  • Edwards
  • Apollo
  • Neuron
  • Bezos
  • Musk
  • SpaceX
  • Terraforming
  • Alpha Centauri
  • Milner
  • Breakthrough Starshot
  • Jules Verne
  • Antimatter
  • Supervolcano: A volcano capable of an eruption hundreds or thousands of times more powerful than an ordinary one. Such eruptions happen once in tens or hundreds of thousands of years and change the climate of the whole planet.
  • Yellowstone: A national park in the United States that sits on top of one of the largest supervolcanoes. Its last super eruption was about 640,000 years ago.
  • Multiplanetary species: The central image of the book: a human race with settlements on more than one planet. Kaku sees this as a way to survive global catastrophes.
  • Goddard: Robert Goddard was an American physicist and inventor, a pioneer of rocketry. In 1926 he launched the world's first liquid-fuel rocket.
  • The New York Times: One of the best known American newspapers, published in New York since 1851.
  • Tsiolkovsky: Konstantin Tsiolkovsky was a self-taught Russian scientist and a schoolteacher from Kaluga, the founder of the theory of spaceflight. He derived the formula used to calculate a rocket's speed.
  • Blue Origin: An American private space company founded by Jeff Bezos in 2000. It also develops reusable rockets.
  • Cosmic radiation: Streams of extremely energetic particles coming from the Sun and from deep space. On Earth the atmosphere and the magnetic field protect us from them; in space they are a danger to health.
  • Polar caps: Icy regions at the poles of Mars. They are made of water ice and frozen carbon dioxide, that is, dry ice.
  • Jakosky: Bruce Jakosky is an American planetary scientist at the University of Colorado who for many years led NASA's MAVEN mission, which studies the atmosphere of Mars.
  • Generation ships: Hypothetical huge ships on which the journey to the stars lasts so long that the children or grandchildren of those who set out are the ones who arrive.
  • Laser porting: Kaku's speculative idea: sending a digital map of the brain by laser beam to a robot on another planet. It is untested and may prove impossible.
  • Connectome: A complete map of the connections between the neurons of a brain. No such map exists yet for the human brain.
  • Kardashev: Nikolai Kardashev was a Soviet and Russian astrophysicist. In 1964 he proposed comparing civilizations by the amount of energy they use.
  • Kardashev scale: A way to compare civilizations by how much energy they use: on the scale of a planet, a star or a galaxy. It is a tool for reasoning, not a measured quantity.
  • Warp drive: A hypothetical engine that would compress space in front of a ship and stretch it behind, to get around the ban on travelling faster than light. So far it exists only on paper.
  • Wormhole: A hypothetical “tunnel” in spacetime that could connect distant points of the universe by a short path. No wormhole has ever been found.
  • Negative energy: An unusual form of energy needed for wormholes and warp drives. Quantum physics allows it in tiny amounts, but no one has produced it on the scale required.

All terms

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