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A Scientist's Notebook
by Gregory Benford

Pascal's Terrible Silence

The silence of those infinite spaces terrifies me.
-- Blaise Pascal, 1623-1662

We moderns have had to confront new varieties of physical infinity, and Pascal's reaction to the scale of creation science was only beginning to unveil still rings true to us.

But Pascal did not cower merely before largeness; he feared its hush.

Perhaps humanity can't stand emptiness, the flip side of infinity. For Pascal feared the meaninglessness of it all, the absence of any hint that human effort had pith and substance. Nearly all sf attempts to answer this supreme agoraphobia by populating the yawning abyss.

The longing for alien contact seems to fulfill a parallel need. Yet this is a curious reassurance, since on the face of it such a discovery will deprive us of what many still believe to be a true uniqueness. So I think the clue behind the longings of UFO fans and Star Trek episodes and endless sf texts is that aliens give us companionship, making the infinities comfy, even talkative.

A truly strange and unknowable alien undercuts this comfortable feeling, and thus is quite rare in sf. Similarly, the use of time in sf so often veers away from truly labyrinthian implications. The infinities of causal loops in Robert Heinlein's classic "By His Bootstraps---" and onward are often seen as horrifying. A standard cliché of such loop stories is that the narrator ends trapped in one, feeling himself tiring, filling with angst and ennui.

But this betrays and denies the nature of a truly fixed causal loop, for the victim caught in one cannot experience loss of energy or accumulation of knowledge--everything really will be the same each cycle. The infinity of time becomes a cage that implicitly denies the premise--but even that seems preferable to the abyss of meaningless repetition.

So what interests me most is sf which does not subvert the infinite. I prefer Oalf Stapledon's Star Maker, which many find hard to read. Their difficulty probably stems from the novel's resolute refusal to ground its vision in concrete detail, to give the feeling of a mapped territory. Instead, immensity is seen abstractly, its ponderous forces unrolling through measureless time.

By contrast, Arthur Clarke's novel 2001 made its approach to the infinite clearly symbolic. Taking another tack, the film 2001 grounded the implied infinity in hard surfaces, such as the eighteenth century bedroom wherein human mortality plays itself out.

Like the alien, the infinite is a subject best crept up on. Much must be implied, the reader must be caught by sudden visions. I attempted something like this in a novel, Against Infinity, only to find much later that an entire symbolic undercurrent seemed to be working to other purposes. The enormous is sometimes a legitimate metaphor for the infinite, but the core of the mystery lies in the difference. Our minds were not built for the truly infinity.

An enormous hush, however, calls forth other demons.

*     *     *

A cliché of post-George Lucas space films are the fighter-pilot zooms and roars in high vacuum. Just about everybody knows this is phony, yet we do not think of all creation as a place without a voice, a vault of no sound. The gleaming galaxy is silent. Stars smashing to supernovas, black holes sucking down whole solar systems in a day—all without a tremor.

Sound is by definition the wave motion of molecules, whether in gas or solid or liquid. No matter-or at least, very little-means no sound.

Between the stars there is about one hydrogen atom in the volume of a sugar cube. That is too little to support a sound wave, because a molecule must smack into another to convey the information that the wave is there.

To be a wave at all implies some reciprocity, a give and take. Under the slight pressure of the wave, gas atoms must move forward, overshoot their place, then return to where they were. Only the wave moves, just as on the surface of the ocean; the sea stays where it was.

That lone hydrogen atom cannot find another hydrogen to thump for a very long time - long after the ostensible wave would have passed. Hence, if something (say, a passing asteroid) shoves on a hydrogen atom, it just takes off, saying nothing to other hydrogens nearby. The asteroid sheds these atoms, like gravel spitting away from the tires of a car; no sinuous motion, no reciprocity between the press of a wave and the inertia of matter.

Between the Earth and the nearest star there lies a vacuum better than any we can produce in the laboratory. Take that sugar cube of volume and push it out, all the way to the nearest star, sweeping up all the hydrogen in the way. That is a fantastic distance, 4.2 light years - that unit itself an everyday synonym for the infinite.

A way to think of it is to imagine the sun as a tennis ball in Times Square, New York. Then the Earth would be a dust mote floating across the street. Alpha Centauri, our nearest neighbor, would be another yellow tennis ball rolling around near Chicago.

Along all that huge distance, the hydrogen swept up by a speeding sugar cube would add up to about a millionth of an ounce, an undetectable weight. So filmy is this gas that it does not function as a gas at all, just a collection of independent atoms.

Of course there is much more flitting between the stars, all kinds of electromagnetic noise as electrons fidget from one atomic energy level to the next. If these revels happen to resonate in the region of wavelengths our eyes have evolved to see, we get to witness the stars' own unleashed furies. Sympathetic electrons in our own retinas dance in response, excited by incoming waves.

For those frequencies we cannot see, our antennas can now pick up the excited buzz of gas turning into stars, or the reverse. In the last century we have thrown open the windows on more and more of this electromagnetic blare, a cacophony descending from all the universe. The cosmic bedlam goes right back to the primordial, faded hiss of hydrogen itself being born right after the Big Bang.

Fred Hoyle offered that name as ridicule, since he preferred his own model of Creation, with matter coming into being at a constant clip, the Steady State Universe. It was a pretty picture, that Creation had no beginning and no end, just a universe swelling from a pinpoint that had already enjoyed an infinite life. Pretty, appealing-which was why so many were drawn to it-and wrong. (A famous motto holds that "Science is the brutal murder of beautiful theories by ugly facts.")

The Big Bang had the last word. But it was wordless, in fact--and soundless, too. Instead of envisioning an explosion, like a hand grenade going off in a phone booth, it is best to think of the Big Bang as all of space and time beginning at a point, and then emerging, cooling, expanding into the space it was making for itself. Call it the Enormous Emergence, though of course in the first unimaginable fraction of a second it was not enormous at all, and took up no more space than your fist.

And it didn't bang, either. There was no source for this Emergence, no one place it started and expanded into another place. It just happened. So, without matter running into other matter to create a coherent wave, there was no sound.

Pascal feared the moral silence of those spaces. He might have preferred that they be angry, the abode of a Satan perhaps, to what science was telling him: that far worse than being malign, the stars were indifferent. We can take on any opponent, but don't ignore us. Show some respect.

Yet in a way that heavenly silence should remind us to respect the fact that our natural world is alive with sound. How come?

*     *     *

When Apollo 8 looped around the moon, giving us our first look at our world, to my mind it justified every penny spent in space. They showed us ourselves whole and entire for the first time, revealed that we lived inside a membrane.

Looking at Earth, you seldom see earth--that is, dirt. You witness instead the skin of air and cloud and sea the planet has learned to wrap about itself. Our planet is a machine that edits its sun, a craft it evolved.

Life began here under a killing sleet of ultraviolet that hammered down from the unedited star just born, its hard glare unblocked by murky layers of methane and carbon dioxide.

Only water vapor intercepted some of the piercing radiation. Its efforts were self-limited, for the fierce energies of ultraviolet split water into hydrogen and oxygen, and the oxygen in turn absorbs exactly those wavelengths of ultraviolet that shatter water.

Only living creatures could do better, by inventing photosynthesis. The first forms to do this had to hide from the biting ultraviolet beneath about ten meters of water. Lakes or ponds seem best for this, since oceans seldom let floating algae stay at a constant depth.

Once these plants started editing the air, the air edited sunlight. Oxygen got fried into ozone at the top of the atmosphere, shielding the evolving forms below. Once oxygen reached about one percent of the air, the non-oxygen breathers started to feel its poisoning sting.

All this took a while. About two billion years passed before oxygen began making itself felt. The oxygen that did come into play was often scooped up by the carbon in the soil, and buried away. The carbon kept being recycled, leaving oxygen below ground, by processes of plate tectonics.

On a world more like Mars than Earth, with tectonics that began and then quickly froze out as the planet cooled, oxygen might have accumulated in the atmosphere much earlier, perhaps in only one hundred million years. Life could get a quicker start on such a world-a possibility still open in our theories of the early eras of Mars.

Once there was about one percent oxygen to shield it, only about six hundred million years ago, life could begin to venture to the top of lakes, ponds, and oceans. Skeletons became common, leaving us plenty of fossils to mark the change.

Oxygen levels still climbed, born of life, until at around ten percent of the atmosphere's mass, its umbrella against ultraviolet allowed forms to climb out onto land. This happened about four hundred million years ago.

Oxygen was the crucial gas, because its atomic bonds stopped the ultraviolet that hammers hard on proteins and the like. Plus, it let the milder sun rays through to feed photosynthesis.

Since this is a universal property of oxygen, it bodes well for planets that can begin with the same sort of unpromising atmosphere we once had. But the crust of the world must cooperate, capturing some but not all the gases that together make an evolving atmosphere.

We still witness the ebb and sway of carbon dioxide in and out of our atmosphere, a tiny but crucial part. Though only a fraction of a percent of the air, it feeds all plant life and regulates the temperature of the surface through the now-famous greenhouse effect. In the long run, a rise in carbon dioxide may warm the Earth enough to stimulate plant growth, which then puts a brake on carbon in the air.

The reverse seems to work, too, with a lower temperature killing plants, so that they cannot pull much carbon from the air. Volcanoes could then replenish it, in time.

All this is like breathing, as the late Lewis Thomas remarked, but on an immense time scale. The cycles of ice ages take at least tens of thousands of years, the "respiration" of the biosphere's largest membrane. Carbon in, carbon out . . .

That this intricate mechanism evolved on its own, though prodded by the slow increase in the sun's luminosity and the continental churn driven by the spinning Earth, is a striking example of coherent organization springing from unthinking processes--spontaneous order on the largest planetary scale.

With it, the Earth resembles an enormous cell, its life mediated by a permeable membrane that edits energy and light. It even selects from among the hailstorm of meteorites that bombard us daily, letting pass without firey death only those larger than Volkswagens.

More subtly, it edits out our own voices. Just as we cannot hear the cataclysms of distant suns, no hint of our own hubbub can escape Earth's airy membrane. The silence above that Pascal feared edits out all our brave talk, all the booming of our significance. The membrane refracts and reflects all our noises back from the top of the air, so that they return to us, dispersed and inaudible, each of our voices spread over whole territories by the time it bounces back from the high reaches.

So there is no way to speak to the stars except through electromagnetic waves. Yet life-here, at least--is engineered for acoustic waves. No creature uses more than a tiny sliver of the electromagnetic spectrum, mostly the visible and the near infrared, where our mammalian bodies radiate. (I've written about aliens who see in the radio wavelengths, for reasons of their local environment, in a novel, Across the Sea of Suns--but I don't think they're likely. I was intrigued by the idea that they might be our co-correspondents in interstellar communication, but we would not guess their nature for a long time, because we thought they had our advanced technology.)

So the membrane has edited us as well, tailoring our extraordinary hearing until in closed conditions we can hear over seven orders of magnitude of sound amplitude.

So Pascal's silence was ordained by evolution. Life sharpened its perception of the waves in its membrane, largely ignoring the electromagnetic discourse of the stars.

*     *     *

Jean Cocteau, in the first volume of his diaries, remarked that Andre Gide "has never experienced the discomfort of infinity." To the reserved French mind of that time perhaps infinity was simply too messy, too unconstrained, to be admitted into experience. European literary society had a habit of wrapping the universe around itself, shutting out the immensities. Jules Verne was the first great French writer of sf, and the last.

So in the end, our ceaseless grappling with infinity demands art of a peculiarly intellectual kind. The essence of enormity must be attacked indirectly, by leaving in the narrative a feeling for the non-centrality of humans themselves, for the prospect that unlimited space and time promises more, finally, than our ultimately futile attempts at closure and domestication.

We talk often, I suspect, to drown out the silence of the spheres.

===THE END===


copyright © 2001 Abbenford Associates

Comments on this column welcome at gbenford@uci.edu, or Physics Dept., Univ. Calif., Irvine, CA 92717


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