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

by Michio Kaku

If the universe is dense enough, then there is enough matter and gravity to attract the distant galaxies and reverse the expansion, so that the Big Crunch becomes a realistic possibility. If the universe lacks sufficient mass, then there is not enough gravity to reverse the expansion and the universe goes into a Big Freeze. The critical density separating these two scenarios is roughly six hydrogen atoms per cubic meter.

A headlamp of known brightness is a “standard candle.” A Type Ia supernova acts as a standard candle, so it’s easy to tell its distance.)

So in addition to the Big Freeze and Big Crunch, a third alternative began to emerge from the data, the Big Rip, which is like the Big Freeze on steroids. It is a vastly accelerated time frame for the life cycle of the universe.

All the devotion, all the inspiration, all the noonday brightness of human genius, are destined to extinction in the vast death of the solar system, and [the] whole temple of man’s achievement must inevitably be buried beneath the debris of a universe in ruins…Only within the scaffolding of these truths, only on the firm foundation of unyielding despair, can the soul’s habitation henceforth be safely built.

For the Earth, the future lies in fire. In five or so billion years we will have the last nice day on our home planet, then the sun will exhaust its hydrogen fuel and expand into a red giant star. Eventually the sun will set the sky on fire. The oceans will boil and the mountains will melt. The Earth will be engulfed by the sun, and will orbit like a burnt-out cinder within its fiery atmosphere. There is a biblical reference that says, from ashes to ashes, dust to dust. Physicists say, from stardust we came, to stardust we will return.

1. In the first epoch, the first billion years after the Big Bang, the universe was filled with hot opaque clouds of ionic molecules, too hot for electrons and protons to condense into atoms. 2. In the second epoch, a billion years after the Big Bang, the universe cooled down enough so that atoms, stars, and galaxies could emerge from the chaos. Empty space suddenly became crystal clear, and stars lit up the universe for the first time. We are living in this era now. 3. In the third epoch, about one hundred billion years after the Big Bang, the stars will have exhausted most of their nuclear fuel. The universe will consist mainly of small red dwarf stars, which burn so slowly that they can shine for trillions of years. 4. In the fourth epoch, trillions of years after the Big Bang, all the stars will finally burn out and the universe will go completely black. Only dead neutron stars and black holes remain. 5. In the fifth epoch, even black holes begin to evaporate and disintegrate, so the universe becomes a sea of nuclear waste and drifting subatomic particles.

The first is the Copernican principle, which simply states that there is nothing special about the Earth. So the Earth is just a piece of cosmic dust wandering aimlessly through the cosmos. It is just a coincidence that the forces of nature are “tuned” just right.

“Can entropy ever be reversed?” the master computer replies each time, “There is insufficient data for a meaningful answer.”