Gregory Benford - The Far Future

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GREGORY BENFORD

THE FAR FUTURE

Little science fiction deals with truly grand perspectives in time. Most

stories and novels envision people much like ourselves, immersed in cultures

that quite resemble ours, and inhabiting worlds which are foreseeable

extensions of the places we now know.

Such landscapes are, of course, easier to envision, more comfortable to the

reader, and simpler for the writer; one can simply mention everyday objects

and let them set the interior stage of the reader's mind.

Yet some of our field's greatest works concern vast perspectives. Most of Olaf

Stapledon's novels (Star Maker, Last And First Men) are set against such

immense backdrops. Arthur C. Clarke's Against the Fall of Night opens over a

billion years in our future. These works have remained in print many decades,

partly because they are rare attempts to "look long" -- to see ourselves

against the scale of evolution itself.

Indeed, H.G. Wells wrote The Time Machine in part as a reaction to the

Darwinian ideas which had swept the intellectual world of comfortable England.

He conflated evolution with a Marxist imagery of racial class separation,

notions that could only play out on the scale of millions of years. His doomed

crab scuttling on a reddened beach was the first great image of the far

future.

Similarly, Stapledon and Clarke wrote in the dawn of modern cosmology, shortly

after Hubble's discovery of universal expansion implied a startlingly large

age of the universe. Cosmologists believed this to be about two billion years

then. From better measurements, we now think it to be at least five times

that. In any case, it was so enormous a time that pretensions of human

importance seemed grotesque. We have been around less than a thousandth of the

universe's age. Much has gone before us, and even more will follow.

In recent decades there have been conspicuously few attempts to approach such

perspectives in literature. This is curious, for such dimensions afford

sweeping vistas, genuine awe. Probably most writers find the severe demands

too daunting. One must understand biological evolution, the physical sciences,

and much else -- all the while shaping a moving human story, which may not

even involve humans as we now know them. Yet there is a continuing audience

for such towering perspectives.

"Thinking long" means "thinking big." Fiction typically focuses on the local

and personal, gaining its power by unities of time and setting. Fashioning

intense stories against huge backdrops is difficult. And humans are special

and idiosyncratic, while the sweep of time is broad, general and uncaring.

We are tied to time, immense stretches of it. Our DNA differs from that of

chimps by only 1.6 percent; we lords of creation are but a hair's breadth from

the jungle. We are the third variety of chimp, and a zoologist from Alpha

Centauri would classify us without hesitation along with the common chimp of

tropical Africa and the pygmy chimp of Zaire. Most of that 1.6 percent may

well be junk, too, of no genetic importance, so the significant differences

are even smaller.

We carry genetic baggage from far back in lost time. We diverged genetically

from the Old World monkeys about 30 million years ago, from gorillas about ten

million years ago, and from the other chimps about seven million years ago.

Only 40 thousand years ago did we wondrous creatures appear -- meaning our

present form, which differs in shape and style greatly from our ancestor

Neanderthals. We roved further, made finer tools, and when we moved into

Neanderthal territory, the outcome was clear; within a short while, no more

Neanderthals.

No other large animal is native to all continents and breeds in all habitats,

from rainforests to deserts to the poles. Among our unique abilities which we

proudly believe led to our success, we seldom credit our propensity to kill

each other, and to destroy our environment--yet there are evolutionary

arguments that these were valuable to us once, leading to pruning of our genes

and ready use of resources.

These same traits now threaten our existence. They also imply that, if we last

into the far future, those deep elements in us will make for high drama,

rueful laughter, triumph and tragedy.

While we have surely been shaped by our environment, our escape from bondage

to our natural world is the great theme of civilization. How will this play

out on the immense scale of many millennia? The environment will surely

change, both locally on the surface of the Earth, and among the heavens. We

shall change with it.

We shall probably meet competition from other worlds, and may fall from

competition to a Darwinian doom. We could erect immense empires and play

Godlike games with vast populations. And surely we could tinker with the

universe in ingenious ways, the inquisitive chimpanzee wrestling whole worlds

to suit his desires. Once we gain great powers, we can confront challenges

undreamed of by Darwin. The universe as a whole is our ultimate opponent.

In the very long run, the astrologers may turn out to be right: our fates may

be determined by the stars. For they are doomed.

Stars are immense reservoirs of energy, dissipating their energy stores into

light as quickly as their bulk allows. Our own star is 4.3 billion years old,

almost halfway through its eleven billion year life span. After that, it shall

begin to burn heavier and heavier elements at its core, growing hotter. Its

atmospheric envelope of already incandescent gas shall heat and swell. From a

mild-mannered, yellow-white star it shall bloat into a reddened giant,

swallowing first Mercury, then Venus, then Earth and perhaps Mars.

H.G. Wells foresaw in The Time Machine a dim sun, with a giant crablike thing

scuttling across a barren beach. While evocative, this isn't what astrophysics

now tells us. But as imagery, it remains a striking reflection upon the deep

problem that the far future holds -- the eventual meaning of human action.

About 4.5 billion years from now, our sun will rage a hundred times brighter.

Half a billion years further on, it will be between 500 and a thousand times

more luminous, and seventy percent larger in radius. The Earth's temperature

depends only slowly on the sun's luminosity (varying as the one fourth root),

so by then our crust will roast at about 1400 degrees Kelvin, room temperature

is 300 Kelvin. The oceans and air will have boiled away, leaving barren plains

beneath an angry sun which covers thirty-five degrees of the sky.

What might humanity -- however transformed by natural selection, or by its own

hand -- do to save itself? Sitting further from the fire might work.

Temperature drops inversely with the square of distance, so Jupiter will be

cooler by a factor of 2.3, Saturn by 3.1. But for a sun 500 times more

luminous than now, the Jovian moons will still be 600 degrees Kelvin (K), and

Saturn's about 450 K. Uranus might work, 4.4 times cooler, a warm but

reasonable 320 K. Neptune will be a brisk 255 K. What strange lives could

transpire in the warmed, deep atmospheres of those gas giants?

Still, such havens will not last. When the sun begins helium burning in

earnest it will fall in luminosity, and Uranus will become a chilly 200 K.

Moving inward to Saturn would work, for it will then be at 300 K, balmy

shirtsleeve weather -- if we have arms by then.

The bumpy slide downhill for our star will see the sun's luminosity fall to

merely a hundred times the present value, when helium burning begins, and the

Earth will simmer at 900 K. After another fifty million years --how loftily

astrophysicists can toss off these immensities! -- as further reactions alter

in the sun's core, it will swell into a red giant again. It will blow off its

outer layers, unmasking the dense, brilliant core that will evolve into a

white dwarf. Earth will be seared by the torrent of escaping gas, and bathed

in piercing ultraviolet light. The white-hot core will then cool slowly.

As the sun eventually simmers down, it will sink to a hundredth of its present

luminosity. Then even Mercury will be a frigid 160 K, and Earth will be a

frozen corpse at 100 K. The solar system, once a grand stage, will be a black

relic beside a guttering campfire.

To avoid this fate, intelligent life can tinker -- at least for a while --

with stellar burning. Our star will get into trouble because it will

eventually pollute its core with the heavier elements that come from burning

hydrogen. In a complex cycle, hydrogen fuses and leaves assorted helium,

lithium, carbon and other elements. With all its hydrogen burned up at its

core, where pressures and temperatures are highest, the sun will begin fusing

helium. This takes higher temperatures, Which the star attains by compressing

under gravity. Soon the helium runs out. The next heavier element fuses.

Carbon bums until the star enters a complex, unstable regime leading to

swelling. (For other stars than ours, there could even be explosions

(supernovas) if its mass is great enough.)

To stave off this fate, a cosmic engineer need only note that at least ninety

percent of the hydrogen in the star is still unburned, when the cycle turns in

desperation to fusing helium. The star's oven lies at the core, and hydrogen

is too light to sink down into it.

Envision a great spoon which can stir the elements in a star, mixing hydrogen

into the nuclear ash at the core. The star could then return to its calmer,

hydrogen-fusing reaction.

No spoon of matter could possibly survive the immense temperatures there, of

course. But magnetic fields can move mass through their rubbery pressures. The

sun's surface displays this, with its magnetic arches and loops which stretch

for thousands of kilometers, tightly clasping hot plasma into tubes and

strands.

If a huge magnetic paddle could reach down into the sun's core and stir it,

the solar life span could extend to perhaps a hundred billion years. To do

this requires immense currents, circulating over coils larger than the sun

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