Макс Тегмарк - Life 3.0 - Being Human in the Age of Artificial Intelligence

So if our old perceived limits of life can be shattered by technology, what are the ultimate limits? How much of our cosmos can come alive? How far can life reach and how long can it last? How much matter can life make use of, and how much energy, information and computation can it extract? These ultimate limits are set not by our understanding, but by the laws of physics. This, ironically, makes it in some ways easier to analyze the long-term future of life than the short-term future.

If our 13.8-billion-year cosmic history were compressed into a week, then the 10,000-year drama of the last two chapters would be over in less than half a second. This means that although we cannot predict if and how an intelligence explosion will unfold and what its immediate aftermath will be like, all this turmoil is merely a brief flash in cosmic history whose details don’t affect life’s ultimate limits. If the post-explosion life is as obsessed as today’s humans are with pushing limits, then it will develop technology to actually reach these limits—because it can. In this chapter, we’ll explore what these limits are, thus getting a glimpse of what the long-term future of life may be like. Since these limits are based on our current understanding of physics, they should be viewed as a lower bound on the possibilities: future scientific discoveries may present opportunities to do even better.

But do we really know that future life will be so ambitious? No, we don’t: perhaps it will become as complacent as a heroin addict or a couch potato merely watching endless reruns of Keeping Up with the Kardashians . However, there is reason to suspect that ambition is a rather generic trait of advanced life. Almost regardless of what it’s trying to maximize, be it intelligence, longevity, knowledge or interesting experiences, it will need resources. It therefore has an incentive to push its technology to the ultimate limits, to make the most of the resources it has. After this, the only way to further improve is to acquire more resources, by expanding into ever-larger regions of the cosmos.

Also, life may independently originate in multiple places in our cosmos. In that case, unambitious civilizations simply become cosmically irrelevant, with ever-larger parts of the cosmic endowment ultimately being taken over by the most ambitious life forms. Natural selection therefore plays out on a cosmic scale and, after a while, almost all life that exists will be ambitious life. In summary, if we’re interested in the extent to which our cosmos can ultimately come alive, we should study the limits of ambition that are imposed by the laws of physics. Let’s do this! Let’s first explore the limits of what can be done with the resources (matter, energy, etc.) that we have in our Solar System, then turn to how to get more resources through cosmic exploration and settlement.

Making the Most of Your Resources

Whereas today’s supermarkets and commodity exchanges sell tens of thousands of items we might call “resources,” future life that’s reached the technological limit needs mainly one fundamental resource: so-called baryonic matter, meaning anything made up of atoms or their constituents (quarks and electrons). Whatever form this matter is in, advanced technology can rearrange it into any desired substances or objects, including power plants, computers and advanced life forms. Let’s therefore begin by examining the limits on the energy that powers advanced life and the information processing that enables it to think.

Building Dyson Spheres

When it comes to the future of life, one of the most hopeful visionaries is Freeman Dyson. I’ve had the honor and pleasure of knowing him for the past two decades, but when I first met him, I felt nervous. I was a junior postdoc chowing away with my friends in the lunchroom of the Institute for Advanced Study in Princeton, and out of the blue, this world-famous physicist who used to hang out with Einstein and Gödel came up and introduced himself, asking if he could join us! He quickly put me at ease, however, by explaining that he preferred eating lunch with young folks over stuffy old professors. Even though he’s ninety-three as I type these words, Freeman is still younger in spirit than most people I know, and the mischievous boyish glint in his eyes reveals that he couldn’t care less about formalities, academic hierarchies or conventional wisdom. The bolder the idea, the more excited he gets.

When we talked about energy use, he scoffed at how unambitious we humans were, pointing out that we could meet all our current global energy needs by harvesting the sunlight striking an area smaller than 0.5% of the Sahara desert. But why stop there? Why even stop at capturing all the sunlight striking Earth, letting most of it get wastefully beamed into empty space? Why not simply put all the Sun’s energy output to use for life?

Inspired by Olaf Stapledon’s 1937 sci-fi classic Star Maker, with rings of artificial worlds orbiting their parent star, Freeman Dyson published a description in 1960 of what became known as a Dyson sphere. 1 Freeman’s idea was to rearrange Jupiter into a biosphere in the form of a spherical shell surrounding the Sun, where our descendants could flourish, enjoying 100 billion times more biomass and a trillion times more energy than humanity uses today.2 He argued that this was the natural next step: “One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star.” If you lived on the inside of a Dyson sphere, there would be no nights: you’d always see the Sun straight overhead, and all across the sky, you’d see sunlight reflecting off the rest of the biosphere, just as you can nowadays see sunlight reflecting off the Moon during the day. If you wanted to see stars, you’d simply go “upstairs” and peer out at the cosmos from the outside of the Dyson sphere.

A low-tech way to build a partial Dyson sphere is to place a ring of habitats in circular orbit around the Sun. To completely surround the Sun, you could add rings orbiting it around different axes at slightly different distances, to avoid collisions. To avoid the nuisance that these fast-moving rings couldn’t be connected to one another, complicating transportation and communication, one could instead build a monolithic stationary Dyson sphere where the Sun’s inward gravitational pull is balanced by the outward pressure from the Sun’s radiation—an idea pioneered by Robert L. Forward and by Colin McInnes. The sphere can be built by gradually adding more “statites”: stationary satellites that counteract the Sun’s gravity with radiation pressure rather than centrifugal forces. Both of these forces drop off with the square of the distance to the Sun, which means that if they can be balanced at one distance from the Sun, they’ll conveniently be balanced at any other distance as well, allowing freedom to park anywhere in our Solar System. Statites need to be extremely lightweight sheets, weighing only 0.77 grams per square meter, which is about 100 times less than paper, but this is unlikely to be a showstopper. For example, a sheet of graphene (a single layer of carbon atoms in a hexagonal pattern resembling chicken wire) weighs a thousand times less than that limit. If the Dyson sphere is built to reflect rather than absorb most of the sunlight, then the total intensity of light bouncing around within it will be dramatically increased, further boosting the radiation pressure and the amount of mass that can be supported in the sphere. Many other stars have a thousandfold and even a millionfold greater luminosity than our Sun, and are therefore able to support correspondingly heavier stationary Dyson spheres.