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

If, despite its best attempts at cosmic engineering, a future civilization concludes that parts of it are doomed to drift out of contact forever, it might simply let them go and wish them well. However, if it has ambitious computing goals that involve seeking the answers to certain very difficult questions, it might instead resort to a slash-and-burn strategy: it could convert the outlying galaxies into massive computers that transform their matter and energy into computation at a frenzied pace, in the hope that before dark energy pushes their burnt-out remnants from view, they could transmit the long-sought answers back to the mother cluster. This slash-and-burn strategy would be particularly appropriate for regions so distant that they can only be reached by the “cosmic spam” method, much to the chagrin of the preexisting inhabitants. Back home in the mother region, the civilization could instead aim for maximum conservation and efficiency to last as long as possible.

How Long Can You Last?

Longevity is something that most ambitious people, organizations and nations aspire to. So if an ambitious future civilization develops superintelligence and wants longevity, how long can it last?

The first thorough scientific analysis of our far future was performed by none less than Freeman Dyson, and table 6.3 summarizes some of his key findings. The conclusion is that unless intelligence intervenes, solar systems and galaxies gradually get destroyed, eventually followed by everything else, leaving nothing but cold, dead, empty space with an eternally fading glow of radiation. But Freeman ends his analysis on an optimistic note: “There are good scientific reasons for taking seriously the possibility that life and intelligence can succeed in molding this universe of ours to their own purposes.”8

I think that superintelligence could easily solve many of the problems listed in table 6.3, since it can rearrange matter into something better than solar systems and galaxies. Oft-discussed challenges such as the death of our Sun in a few billion years won’t be showstoppers, since even a relatively low-tech civilization can easily move to low-mass stars that last for over 200 billion years. Assuming that superintelligent civilizations build their own power plants that are more efficient than stars, they may in fact want to prevent star formation to conserve energy: even if they use a Dyson sphere to harvest all the energy output during a star’s main lifetime (recouping about 0.1% of the total energy), they may be unable to keep much of the remaining 99.9% of the energy from going to waste when very hefty stars die. A heavy star dies in a supernova explosion from which most of the energy escapes as elusive neutrinos, and for very heavy stars, a large amount of mass gets wasted by forming a black hole from which the energy takes 10 67years to seep out. What WhenCurrent age of our Universe 10 10years Dark energy pushes most galaxies out of reach 10 11years Last stars burn out 10 14years Planets detached from stars 10 15years Stars detached from galaxies 10 19years Decay of orbits by gravitational radiation 10 20years Protons decay (at the earliest) > 10 34years Stellar-mass black holes evaporate 10 67years Supermassive black holes evaporate 10 91years All matter decays to iron 10 1500years All matter forms black holes, which then evaporate 10 1026years

Table 6.3: Estimates for the distant future, all but the 2nd and 7th made by Freeman Dyson. He made these calculations before the discovery of dark energy, which may enable several types of “cosmocalypse” in 10 10–10 11years. Protons may be completely stable; if not, experiments suggest it will take over 10 34years for half of them to decay.

As long as superintelligent life hasn’t run out of matter/energy, it can keep maintaining its habitat in the state it desires. Perhaps it can even discover a way to prevent protons from decaying using the so-called watched-pot effect of quantum mechanics, whereby the decay process is slowed by making regular observations. There is, however, a potential showstopper: a cosmocalypse destroying our entire Universe, perhaps as soon as 10–100 billion years from now. The discovery of dark energy and progress in string theory has raised new cosmocalypse scenarios that Freeman Dyson wasn’t aware of when he wrote his seminal paper.

So how’s our Universe going to end, billions of years from now? I have five main suspects for our upcoming cosmic apocalypse, or cosmocalypse, illustrated in figure 6.9: the Big Chill, the Big Crunch, the Big Rip, the Big Snap and Death Bubbles. Our Universe has now been expanding for about 14 billion years. The Big Chill is when our Universe keeps expanding forever, diluting our cosmos into a cold, dark and ultimately dead place; this was viewed as the most likely outcome back when Freeman wrote that paper. I think of it as the T. S. Eliot option: “This is the way the world ends / Not with a bang but a whimper.” If you, like Robert Frost, prefer the world to end in fire rather than ice, then cross your fingers for the Big Crunch, where the cosmic expansion is eventually reversed and everything comes crashing back together in a cataclysmic collapse akin to a backward Big Bang. Finally, the Big Rip is like the Big Chill for the impatient, where our galaxies, planets and even atoms get torn apart in a grand finale a finite time from now. Which of these three should you bet on? That depends on what the dark energy, which makes up about 70% of the mass of our Universe, will do as space continues to expand. It can be any one of the Chill, Crunch or Rip scenarios, depending on whether the dark energy sticks around unchanged, dilutes to negative density or anti-dilutes to higher density, respectively. Since we still have no clue what dark energy is, I’ll just tell you how I’d bet: 40% on the Big Chill, 9% on the Big Crunch and 1% on the Big Rip.

Figure 6.9: We know that our Universe began with a hot Big Bang 14 billion years ago, expanded and cooled, and merged its particles into atoms, stars and galaxies. But we don’t know its ultimate fate. Proposed scenarios include a Big Chill (eternal expansion), a Big Crunch (recollapse), a Big Rip (an infinite expansion rate tearing everything apart), a Big Snap (the fabric of space revealing a lethal granular nature when stretched too much), and Death Bubbles (space “freezing” in lethal bubbles that expand at the speed of light).

What about the other 50% of my money? I’m saving it for the “none of the above” option, because I think we humans need to be humble and acknowledge that there are basic things we still don’t understand. The nature of space, for example. The Chill, Crunch and Rip endings all assume that space itself is stable and infinitely stretchable. We used to think of space as just the boring static stage upon which the cosmic drama unfolds. Then Einstein taught us that space is really one of the key actors: it can curve into black holes, it can ripple as gravitational waves and it can stretch as an expanding universe. Perhaps it can even freeze into a different phase much like water can, with fast-expanding death bubbles of the new phase offering another wild-card cosmocalypse candidate. If death bubbles are possible, they would probably expand at the speed of light, just like the growing sphere of cosmic spam from a maximally aggressive civilization.

Moreover, Einstein’s theory says that space stretching can always continue, allowing our Universe to approach infinite volume as in the Big Chill and Big Rip scenarios. This sounds a bit too good to be true, and I suspect that it is. A rubber band looks nice and continuous, just like space, but if you stretch it too much, it snaps. Why? Because it’s made of atoms, and with enough stretching, this granular atomic nature of the rubber becomes important. Could it be that space too has some sort of granularity on a scale that’s simply too small for us to have noticed? Quantum gravity research suggests that it doesn’t make sense to talk about traditional three-dimensional space on scales smaller than about 10 -34meters. If it’s really true that space can’t be stretched indefinitely without undergoing a cataclysmic “Big Snap,” then future civilizations may wish to relocate to the largest non-expanding region of space (a huge galaxy cluster) that they can reach.