PROOF

Hal Clement

Astounding, June 1942
Kron held his huge freighter motionless, feeling forward for outside contact. The tremendous interplay of magnetic and electrostatic fields just beyond the city's edge was as clearly perceptible to his senses as the city itself—a mile-wide disk ringed with conical field towers, stretching away behind and to each side. The ship was poised between two of the towers; immediately behind it was the field from which Kron had just taken off. The area was covered with cradles of various forms—cup-shaped receptacles which held city craft like Kron's own; long, boat-shaped hollows wherein reposed the cigarlike vessels which plied between the cities; and towering skeleton frameworks which held upright the slender double cones that hurtled across the dark, lifeless regions between stars.
Beyond the landing field was the city proper; the surface of the disk was covered with geometrically shaped buildings—cones, cylinders, prisms, and hemispheres, jumbled together.
Kron could "see" all this as easily as a human being in an airplane can see New York; but no human eyes could have perceived this city, even if a man could have existed anywhere near it. The city, buildings and all, glowed a savage, white heat; and about and beyond it—a part of it, to human eyes—raged the equally dazzling, incandescent gases of the solar photosphere.
The freighter was preparing to launch itself into that fiery ocean; Kron was watching the play of the artificial reaction fields that supported the city, preparatory to plunging through them at a safe moment.
There was considerable risk of being flattened against the edge of the disk if an inauspicious choice was made, but Kron was an experienced flier, and slipped past the barrier with a sudden, hurtling acceleration that would have pulped any body of flesh and bone. The outer fringe of the field flung the globe sharply downward; then it was free, and the city was dwindling above them.
Kron and four others remained at their posts; the rest of the crew of thirty relaxed, their spherical bodies lying passive in the cuplike rests distributed through the ship, bathing in the fierce radiance on which those bodies fed, and which was continually streaming from a three-inch spheroid at the center of the craft. That an artificial source of energy should be needed in such an environment may seem strange, but to these creatures the outer layers of the Sun were far more inhospitable to life than is the stratosphere of Earth to human beings.
They had evolved far down near the solar core, where pressures and temperatures were such that matter existed in the "collapsed" state characteristic of the entire mass of white dwarf stars. Their bodies were simply constructed: a matrix of close-packed electrons—really an unimaginably dense electrostatic field, possessing quasi-solid properties—surrounded a core of neutrons, compacted to the ultimate degree. Radiation of sufficient energy, falling on the "skin," was stabilized, altered to the pattern and structure of neutrons; the tiny particles of neutronium which resulted were borne along a circulatory system—of magnetic fields, instead of blood—to the nucleus, where it was stored.
The race had evolved to the point where no material appendages were needed. Projected beams and fields of force were their limbs, powered by the annihilation of some of their own neutron substance. Their strange senses gave them awareness not only of electromagnetic radiation, permitting them to "see" in a more or less normal fashion, but also of energies still undreamed of by human scientists. Kron, hundreds of miles below the city now, was still dimly aware of its location, though radio waves, light and gamma rays were all hopelessly fogged in the clouds of free electrons. At his goal, far down in the solar interior, "seeing" conditions would be worse—anything more than a few hundred yards distant would be quite indetectable even to him.
Poised beside Kron, near the center of the spheroidal sunship, was another being. Its body was ovoid in shape, like that of the Solarian, but longer and narrower, while the ends were tipped with pyramidal structures of neutronium, which projected through the "skin." A second, fainter static aura enveloped the creature outside the principal surface; and as the crew relaxed in their cups, a beam of energy from this envelope impinged on Kron's body. It carried a meaning, transmitting a clear thought from one being to the other.
"I still find difficulty in believing my senses," stated the stranger. "My own worlds revolve about another which is somewhat similar to this; but such a vast and tenuous atmosphere is most unlike conditions at home. Have you ever been away from Sol?"
"Yes," replied Kron, "I was once on the crew of an interstellar projectile. I have never seen your star, however; my acquaintance with it is entirely through hearsay. I am told it consists almost entirely of collapsed matter, like the core of our own; but there is practically no atmosphere. Can this be so? I should think, at the temperature necessary for life, gases would break free of the core and form an envelope."
"They tend to do so, of course," returned the other, "but our surface gravity is immeasurably greater than anything you have here; even your core pull is less, since it is much less dense than our star. Only the fact that our worlds are small, thus causing a rapid diminution of gravity as one leaves them, makes it possible to get a ship away from them at all; atoms, with only their original velocities, remain within a few miles of the surface.
"But you remind me of my purpose on this world—to check certain points of a new theory concerning the possible behavior of aggregations of normal atoms. That was why I arranged a trip on your flier; I have to make density, pressure, temperature, and a dozen other kinds of measurements at a couple of thousand different levels, in your atmosphere. While I'm doing it, would you mind telling me why you make these regular trips—and why, for that matter, you live so far above your natural level? I should think you would find life easier below, since there would be no need to remain in sealed buildings, or to expend such a terrific amount of power in supporting your cities."
Kron's answer was slow.
"We make the journeys to obtain neutronium. It is impossible to convert enough power from the immediate neighborhood of the cities to support them; we must descend periodically for more, even though our converters take so much as to lower the solar temperature considerably for thousands of miles around each city.
"The trips are dangerous—you should have been told that. We carry a crew of thirty, when two would be enough to man this ship, for we must fight, as well as fly. You spoke truly when you said that the lower regions of Sol are our natural home; but for aeons we have not dared to make more than fleeting visits, to steal the power which is life to us.
"Your little worlds have been almost completely subjugated by your people, Sirian; they never had life forms sufficiently powerful to threaten seriously your domination. But Sol, whose core alone is far larger than the Sirius B pair, did develop such creatures. Some are vast, stupid, slow-moving, or immobile; others are semi-intelligent, and rapid movers; all are more than willing to ingest the ready-compacted neutronium of another living being."
Kron's tale was interrupted for a moment, as the Sirian sent a ray probing out through the ship's wall, testing the physical state of the inferno beyond. A record was made, and the Solarian resumed.
"We, according to logical theory, were once just such a race—of small intelligence, seeking the needs of life among a horde of competing organisms. Our greatest enemy was a being much like ourselves in size and power—just slightly superior in both ways. We were somewhat ahead in intelligence, and I suppose we owe them some thanks—without the competition they provided, we should not have been forced to develop our minds to their present level. We learned to cooperate in fighting them, and from that came the discovery that many of us together could handle natural forces that a single individual could not even approach, and survive. The creation of force effects that had no counterpart in nature was the next step; and, with the understanding of them, our science grew.
"The first cities were of neutronium, like those of today, but it was necessary to stabilize the neutrons with fields of energy; at core temperature, as you know, neutronium is a gas. The cities were spherical and much smaller than our present ones. For a long time, we managed to defend them.
"But our enemies evolved, too; not in intelligence, but in power and fecundity. With overspecialization of their physical powers, their mentalities actually degenerated; they became little more than highly organized machines, driven, by an age-old enmity toward our race, to seek us out and destroy us. Their new powers at last enabled them to neutralize, by brute force, the fields which held our cities in shape; and then it was that, from necessity, we fled to the wild, inhospitable upper regions of Sol's atmosphere. Many cities were destroyed by the enemy before a means of supporting them was devised; many more fell victims to forces which we generated, without being able to control, in the effort. The dangers of our present-day trips seem trivial beside those our ancestors braved, in spite of the fact that ships not infrequently fail to return from their flights. Does that answer your question?"
The Sirian's reply was hesitant. "I guess it does. You of Sol must have developed far more rapidly than we, under that drive; your science, I know, is superior to ours in certain ways, although it was my race which first developed space flight."
"You had greater opportunities in that line," returned Kron. "Two small stars, less than a diameter apart, circling a larger one at a distance incomparably smaller than the usual interstellar interval, provided perfect ground for experimental flights; between your world and mine, even radiation requires some one hundred and thirty rotations to make the journey, and even the nearest other star is almost half as far.
"But enough of this—history is considered by too many to be a dry subject. What brings you on a trip with a power flier? You certainly have not learned anything yet which you could not have been told in the city."
During the conversation, the Sirian had periodically tested the atmosphere beyond the hull. He spoke, rather absently, as though concentrating on something other than his words.
"I would not be too sure of that, Solarian. My measurements are of greater delicacy than we have ever before achieved. I am looking for a very special effect, to substantiate or disprove an hypothesis which I have recently advanced—much to the detriment of my prestige. If you are interested, I might explain: laugh afterward if you care to—you will not be the first.
"The theory is simplicity itself. It has occurred to me that matter—ordinary substances like iron and calcium—might actually take on solid form, like neutronium, under the proper conditions. The normal gas, you know, consists of minute particles traveling with considerable speed in all directions. There seems to be no way of telling whether or not these atoms exert appreciable forces on each other; but it seems to me that if they were brought closely enough together, or slowed down sufficiently, some such effects might be detected."
"How, and why?" asked Kron. "If the forces are there, why should they not be detectable under ordinary conditions?"
"Tiny changes in velocity due to mutual attraction or repulsion would scarcely be noticed when the atomic speeds are of the order of hundreds of kilometers per second," returned the Sirian. "The effects I seek to detect are of a different nature. Consider, please. We know the sizes of the various atoms, from their radiations. We also know that, under normal conditions, a given mass of any particular gas fills a certain volume. If, however, we surround this gas with an impenetrable container and exert pressure, that volume decreases. We would expect that decrease to be proportional to the pressure, except for an easily determined constant due to the size of the atoms, if no interatomic forces existed; to detect such forces, I am making a complete series of pressure-density tests, more delicate than any heretofore, from the level of your cities down to the neutron core of your world.
"If we could reduce the kinetic energy of the atoms—slow down their motions of translation—the task would probably be simpler; but I see no way to accomplish that. Perhaps, if we could negate nearly all of that energy, the interatomic forces would actually hold the atoms in definite relative positions, approximating the solid state. It was that somewhat injudicious and perhaps too imaginative suggestion which caused my whole idea to be ridiculed on Sirius."
The ship dropped several hundred miles in the few seconds before Kron answered; since gaseous friction is independent of change in density, the high pressures of the regions being penetrated would be no bar to high speed of flight. Unfortunately, the viscosity of a gas does increase directly as the square root of its temperature; and at the lower levels of the sun, travel would be slow.
"Whether or not our scientists will listen to you, I cannot say," said Kron finally. "Some of them are a rather imaginative crowd, I guess, and none of them will ignore any data you may produce.
"I do not laugh, either. My reason will certainly interest you, as your theory intrigues me. It is the first time anyone has accounted even partly for the things that happened to us on one of my flights."
The other members of the crew shifted slightly on their cradles; a ripple of interest passed through them, for all had heard rumors and vague tales of Kron's time in the space carrier fleets. The Sirian settled himself more comfortably; Kron dimmed the central globe of radiance a trifle, for the outside temperature was now considerably higher, and began the tale.

"This happened toward the end of my career in space. I had made many voyages with the merchant and passenger vessels, had been promoted from the lowest ranks, through many rotations, to the post of independent captain. I had my own cruiser—a special long-period explorer, owned by the Solarian government. She was shaped like our modern interstellar carriers, consisting of two cones, bases together, with the field ring just forward of their meeting point. She was larger than most, being designed to carry fuel for exceptionally long flights,
"Another cruiser, similar in every respect, was under the command of a comrade of mine, named Akro; and the two of us were commissioned to transport a party of scientists and explorers to the then newly discovered Fourth System, which lies, as you know, nearly in the plane of the solar equator, but about half again as distant as Sirius.
"We made good time, averaging nearly half the speed of radiation, and reached the star with a good portion of our hulls still unconsumed. We need not have worried about that, in any case; the star was denser even than the Sirius B twins, and neutronium was very plentiful. I restocked at once, plating my inner walls with the stuff until they had reached their original thickness, although experience indicated that the original supply was ample to carry us either back to Sol, to Sirius, or to Procyon B.
"Akro, at the request of the scientists, did not refuel. Life was present on the star, as it seems to be on all stars where the atomic velocities and the density are high enough; and the biologists wanted to bring back specimens. That meant that room would be needed, and if Akro replated his walls to normal thickness that room would be lacking—as I have mentioned, these were special long-range craft, and a large portion of their volume consisted of available neutronium.
"So it happened that the other ship left the Fourth System with a low, but theoretically sufficient, stock of fuel, and half a dozen compartments filled with specimens of alien life. I kept within detection distance at all times, in case of trouble, for some of those life forms were as dangerous as those of Sol, and, like them, all consumed neutronium. They had to be kept well under control to safeguard the very walls of the ship, and it is surprisingly difficult to make a wild beast, surrounded by food, stay on short rations.
"Some of the creatures proved absolutely unmanageable; they had to be destroyed. Others were calmed by lowering the atomic excitation of their compartments, sending them into a stupor; but the scientists were reluctant to try that in most cases, since not all of the beings could stand such treatment.
"So, for nearly four hundred Solar rotations, Akro practically fought his vessel across space—fought successfully. He managed on his own power until we were within a few hundred diameters of Sol; but I had to help him with the landing—or try to, for the landing was never made.
"It may seem strange, but there is a large volume of space in the neighborhood of this sun which is hardly ever traversed. The normal landing orbit arches high over one of the poles of rotation, enters atmosphere almost tangentially somewhere between that pole and the equator, and kills as much as remains of the ship's velocity in the outer atmospheric layers. There is a minimum of magnetic interference that way, since the flier practically coasts along the lines of force of the Solar magnetic field.
"As a result, few ships pass through the space near the plane of the Solar equator. One or two may have done so before us, and I know of several that searched the region later; but none encountered the thing which we found.
"About the time we would normally have started correcting our orbits for a tangential landing, Akro radiated me the information that he could not possibly control his ship any farther with the power still available to him. His walls were already so thin that radiation loss, ordinarily negligible, was becoming a definite menace to his vessel. All his remaining energy would have to be employed in keeping the interior of his ship habitable.
"The only thing I could do was to attach our ships together with an attractor beam, and make a nearly perpendicular drop to Sol. We would have to take our chances with magnetic and electrostatic disturbances in the city-supporting fields which cover so much of the near-equatorial zones, and try to graze the nucleus of the Sun instead of its outer atmosphere, so that Akro could replenish his rapidly failing power.
"Akro's hull was radiating quite perceptibly now; it made an easy target for an attractor. We connected without difficulty, and our slightly different linear velocities caused us to revolve slowly about each other, pivoting on the center of mass of our two ships. I cut off my driving fields, and we fell spinning toward Sol.
"I was becoming seriously worried about Akro's chances of survival. The now-alarming energy loss through his almost consumed hull threatened to exhaust his supply long before we reached the core; and we were still more than a hundred diameters out. I could not give him any power; we were revolving about each other at a distance of about one-tenth of a Solar diameter. To lessen that distance materially would increase our speed of revolution to a point where the attractor could not overcome centrifugal force; and I had neither power nor time to perform the delicate job of exactly neutralizing our rotary momentum without throwing us entirely off course. All we could do was hope.
"We were somewhere between one hundred and one hundred and fifty diameters out when there occurred the most peculiar phenomenon I have ever encountered. The plane of revolution of our two ships passed near Sol, but was nearly perpendicular to the Solar equator; at the time of which I speak, Akro's ship was almost directly between my flier and the Sun. Observations had just shown that we were accelerating Sunward at an unexpectedly high pace, when a call came from Akro.
" ‘Kron! I am being pulled away from your attractor! There is a large mass somewhere near, for the pull is gravitational, but it emits no radiation that I can detect. Increase your pull, if you can; I cannot possibly free myself alone.'
"I did what I could, which was very little. Since we did not know the location of the disturbing dark body, it was impossible to tell just what I should do to avoid bringing my own or Akro's vessel too close. I think now that if I had released him immediately he would have swung clear, for the body was not large, I believe. Unfortunately, I did the opposite, and nearly lost my own ship as well. Two of my crew were throwing as much power as they could convert and handle into the attractor, and trying to hold it on the still easily visible hull of Akro's ship; but the motions of the latter were so peculiar that aiming was a difficult task. They held the ship as long as we could see it; but quite suddenly the radiations by means of which we perceived the vessel faded out, and before we could find a band which would get through, the sudden cessation of our centripetal acceleration told us that the beam had slipped from its target.
"We found that electromagnetic radiations of wave lengths in the octave above H-alpha would penetrate the interference, and Akro's hull was leaking energy enough to radiate in that band. When we found him, however, we could scarcely believe our senses; his velocity was now nearly at right angles to his former course, and his hull radiation had become far weaker. What terrific force had caused this acceleration, and what strange field was blanketing the radiation, were questions none of us could answer.
"Strain as we might, not one of us could pick up an erg of radiant energy that might emanate from the thing that had trapped Akro. We could only watch, and endeavor to plot his course relative to our own, at first. Our ships were nearing each other rapidly, and we were attempting to determine the time and distance of closest approach, when we were startled by the impact of a communicator beam. Akro was alive! The beam was weak, very weak, showing what an infinitesimal amount of power he felt he could spare. His words were not encouraging.
" `Kron! You may as well cut your attractor, if you are still trying to catch me. No power that I dare apply seems to move me perceptibly in any direction from this course. We are all badly shocked, for we hit something that felt almost solid. The walls, even, are strained, and may go at any time.'
" `Can you perceive anything around you?' I returned. `You seem to us to be alone in space, though something is absorbing most of your radiated energy. There must be energies in the cosmos of which we have never dreamed, simply because they did not affect our senses. What do your scientists say?'
" `Very little,' was the answer. `They have made a few tests, but they say that anything they project is absorbed without reradiating anything useful. We seem to be in a sort of energy vacuum—it takes everything and returns nothing.'
"This was the most alarming item yet. Even in free space, we had been doubtful of Akro's chances of survival; now they seemed reduced to the ultimate zero.
"Meanwhile, our ships were rapidly approaching each other. As nearly as my navigators could tell, both vessels were pursuing almost straight lines in space. The lines were nearly perpendicular but did not lie in a common plane; their minimum distance apart was about one one-thousandth of a Solar diameter. His velocity seemed nearly constant, while I was accelerating Sunward. It seemed that we would reach the near-intersection point almost simultaneously, which meant that my ship was certain to approach the energy vacuum much too closely. I did not dare to try to pull Akio free with an attractor; it was only too obvious that such an attempt could only end in disaster for both vessels. If he could not free himself, he was lost.
"We could only watch helplessly as the point of light marking the position of Akro's flier swept closer and closer. At first, as I have said, it seemed perfectly free in space; but as we looked, the region around it began to radiate feebly. There was nothing recognizable about the vibrations, simply a continuous spectrum, cut off by some interference just below the H-alpha wave length and, at the other end, some three octaves higher. As the emission grew stronger, the visible region around the stranded ship grew larger, fading into nothingness at the edges. Brighter and broader the patch of radiance grew, as we swept toward it."

That same radiance was seriously inconveniencing Gordon Aller, who was supposed to be surveying for a geological map of northern Australia. He was camped by the only waterhole in many miles, and had stayed up long after dark preparing his cameras, barometer, soil kit, and other equipment for the morrow's work.
The arrangement of instruments completed, he did not at once retire to his blankets. With his back against a smooth rock, and a short, blackened pipe clenched in his teeth, he sat for some time, pondering. The object of his musing does not matter to us; though his eyes were directed heavenward, he was sufficiently accustomed to the southern sky to render it improbable that he was paying much attention to its beauties.
However that may be, his gaze was suddenly attracted to the zenith. He had often seen stars which appeared to move when near the edge of his field of vision—it is a common illusion; but this one continued to shift as he turned his eyes upward.
Not far from Achernar was a brilliant white point, which brightened as Aller watched it. It was moving slowly northward, it seemed; but only a moment was needed for the man to realize that the slowness was illusory. The thing was slashing almost vertically downward at an enormous speed, and must strike Earth not far from his camp.
Aller was not an astronomer, and had no idea of astronomical distances or speeds. He may be forgiven for thinking of the object as traveling perhaps as fast as a modern fighting plane, and first appearing at a height of two or three miles. The natural conclusion from this belief was that the crash would occur within a few hundred feet of the camp. Aller paled; he had seen pictures of the Devil's Pit in Arizona.
Actually, of course, the meteor first presented itself to his gaze at a height of some eighty miles, and was then traveling at a rate of many miles per second relative to Earth. At that speed, the air presented a practically solid obstacle to its flight, and the object was forced to a fairly constant velocity of ten or twelve hundred yards a second while still nearly ten miles from Earth's surface. It was at that point that Aller's eyes caught up with and succeeded in focusing upon the celestial visitor.
That first burst of light had been radiated by the frightfully compressed and heated air in front of the thing; as the original velocity departed, so did the dazzling light. Aller got a clear view of the meteor at a range of less than five miles, for perhaps ten seconds before the impact. It was still incandescent, radiating a bright cherry-red; this must have been due to the loss from within, for so brief a contact even with such highly heated air could not have warmed the sunship's neutronium walls a measurable fraction of a degree.
Aller felt the ground tremble as the vessel struck. A geyser of earth, barely visible in the reddish light of the hull, spouted skyward, to fall back seconds later with a long drawn-out rumble. The man stared at the spot, two miles away, which was still giving off a faint glow. Were "shooting stars" as regularly shaped as that? He had seen a smooth, slender body, more than a hundred feet in length, apparently composed of two cones of unequal length, joined together at the bases. Around the longer cone, not far from the point of juncture, was a thick bulging ring; no further details were visible at the distance from which he had observed. Aller's vague recollections of meteorites, seen in various museums, brought images of irregular, clinkerlike objects before his mind's eye. What, then, could this thing be?
He was not imaginative enough to think for a moment of any possible extraterrestrial source for an aircraft; when it did occur to him that the object was of artificial origin, he thought more of some experimental machine produced by one of the more progressive Earth nations.
At the thought, Aller strapped a first-aid kit to his side and set out toward the crater, in the face of the obvious fact that nothing human could possibly have survived such a crash. He stumbled over the uneven terrain for a quarter of a mile, and then stopped on a small rise of ground to examine more closely the site of the wreck.
The glow should have died by this time, for Aller had taken all of ten minutes to pick his way those few hundred yards; but the dull-red light ahead had changed to a brilliant-orange radiance against which the serrated edges of the pit were clearly silhouetted. No flames were visible; whence came the increasing heat? Aller attempted to get closer, but a wave of frightfully hot air blistered his face and hands, and drove him back. He took up a station near his former camp, and watched.
If the hull of the flier had been anywhere near its normal thickness, the tremendous mass of neutronium would have sunk through the hardest of rocks as though they were liquid. There was, however, scarcely more than a paper thickness of the substance at any part of the walls; and an upthrust of adamantine volcanic rock not far beneath the surface of the desert proved thick enough to absorb the sunship's momentum and to support its still enormous weight. Consequently, the ship was covered only by a thin layer of powdered rock which had fallen back into the crater. The disturbances arising from the now extremely rapid loss of energy from Akro's ship were, as a result, decidedly visible from the surface.
The hull, though thin, was still intact; but its temperature was now far above the melting point of the surrounding rocks. The thin layer of pulverized material above the ship melted and flowed away almost instantly, permitting free radiation to the air above; and so enormous is the specific heat of neutronium that no perceptible lowering of hull temperature occurred.
Aller, from his point of observation, saw the brilliant fan of light that sprang from the pit as the flier's hull was exposed—the vessel itself was invisible to him, since he was only slightly above the level of the crater's mouth. He wondered if the impact of the "meteor" had released some pent-up volcanic energy, and began to doubt, quite justifiably, if he was at a safe distance. His doubts vanished and were replaced by certainty as the edges of the crater began to glow dull-red, then bright-orange, and slowly subsided out of sight. He began packing the most valuable items of his equipment, while a muted, continuous roaring and occasional heavy thuds from the direction of the pit admonished him to hasten.
When he straightened up, with the seventy-pound pack settled on his shoulders, there was simply a lake of lava where the crater had been. The fiery area spread even as he watched; and without further delay he set off on his own back trail. He could see easily, by the light diffused from the inferno behind him; and he made fairly good time, considering his burden and the fact that he had not slept since the preceding night.
The rock beneath Akro's craft was, as we have said, extremely hard. Since there was relatively free escape upward for the constantly liberated energy, this stratum melted very slowly, gradually letting the vessel sink deeper into the earth. What would have happened if Akro's power supply had been greater is problematical; Aller can tell us only that some five hours after the landing, as he was resting for a few moments near the top of a rocky hillock, the phenomenon came to a cataclysmic end.
A quivering of the earth beneath him caused the surveyor to look back toward his erstwhile camp. The lake of lava, which by this time was the better part of a mile in breadth, seemed curiously agitated. Aller, from his rather poor vantage point, could see huge bubbles of pasty lava hump themselves up and burst, releasing brilliant clouds of vapor. Each cloud illuminated earth and sky before cooling to invisibility, so that the effect was somewhat similar to a series of lightning flashes.
For a short time—certainly no longer than a quarter of a minute—Aller was able to watch as the activity increased. Then a particularly violent shock almost flung him from the hilltop, and at nearly the same instant the entire volume of molten rock fountained skyward. For an instant it seemed to hang there, a white, raging pillar of liquid and gas; then it dissolved, giving way before the savage thrust of the suddenly released energy below. A tongue of radiance, of an intensity indescribable in mere words, stabbed upward, into and through the lava, volatilizing it instantly. A dozen square miles of desert glowed white, then an almost invisible violet, and disappeared in superheated gas. Around the edges of this region, great gouts of lava and immense fragments of solid rock were hurled to all points of the compass.
Radiation exerts pressure; at the temperature found in the cores of stars, that pressure must be measured in thousands of tons per square inch. It was this thrust, rather than the by no means negligible gas pressure of the boiling lava, which wrought most of the destruction.
Aller saw little of what occurred. When the lava was hurled upward, he had flung an arm across his face to protect his eyes from the glare. That act unquestionably saved his eyesight, as the real flash followed; as it was, his body was seared and blistered through his clothing. The second, heavier shock knocked his feet from under him, and he half crawled, half rolled down to the comparative shelter of the little hill. Even here, gusts of hot air almost cooked him; only the speed with which the phenomenon ended saved his life.
Within minutes, both the temblors and the hot winds had ceased; and he crawled painfully to the hilltop again to gaze wonderingly at the five-mile-wide crater, ringed by a pile of tumbled, still-glowing rock fragments.
Far beneath that pit, shards of neutronium, no more able to remain near the surface than the steel pieces of a wrecked ocean vessel can float on water, were sinking through rock and metal to a final resting place at Earth's heart.

"The glow spread as we watched, still giving no clue to the nature of the substance radiating it," continued Kron. "Most of it seemed to originate between us and Akro's ship; Akro himself said that but little energy was being lost on the far side. His messages, during that last brief period as we swept by our point of closest approach, were clear—so clear that we could almost see as he did the tenuous light beyond the ever-thinning walls of his ship; the light that represented but a tiny percentage of the energy being sucked from the hull surface.
"We saw, as though with his own senses, the tiny perforation appear near one end of the ship; saw it extend, with the speed of thought, from one end of the hull to the other, permitting the free escape of all the energy in a single instant; and, from our point of vantage, saw the glowing area where the ship had been suddenly brightened, blazing for a moment almost as brightly as a piece of Sun matter.
"In that moment, every one of us saw the identifying frequencies as the heat from Akro's disrupted ship raised the substance which had trapped him to an energy level which permitted atomic radiation. Every one of us recognized the spectra of iron, of calcium, of carbon and silicon and a score of the other elements—Sirian, I tell you that that `trapping field' was matter—matter in such a state that it could not radiate, and could offer resistance to other bodies in exactly the fashion of a solid. I thought, and have always thought, that some strange field of force held the atoms in their `solid' positions; you have convinced me that I was wrong. The `field' was the sum of the interacting atomic forces which you are trying to detect. The energy level of that material body was so low that those forces were able to act without interference. The condition you could not conceive of reaching artificially actually exists in Nature!"
"You go too fast, Kron," responded the Sirian. "Your first idea is far more likely to be the true one. The idea of unknown radiant or static force fields is easy to grasp; the one you propose in its place defies common sense. My theories called for some such conditions as you described, granted the one premise of a sufficiently low energy level; but a place in the real universe so devoid of energy as to absorb that of a well-insulated interstellar flier is utterly inconceivable. I have assumed your tale to be true as to details, though you offer neither witnesses nor records to support it; but I seem to have heard that you have somewhat of a reputation as an entertainer, and you seem quick-witted enough to have woven such a tale on the spot, purely from the ideas I suggested. I compliment you on the tale, Kron; it was entrancing; but I seriously advise you not to make anything more out of it. Shall we leave it at that, my friend?"
"As you will," replied Kron.