Like a college professor reading off routine announcements at the beginning of class, Dihn Ruuu went on, “It is with great pleasure that I state that the home world of the Mirt Korp Ahm does in fact still exist, and neither it nor its star have been destroyed, despite the impossibility of locating them that I experienced. According to communications received on this planet 13,595,486 years ago, the Mirt Korp Ahm embarked on a project at that time for the transformation of their home system into an enclosed sphere permitting full utilization of the solar energy. An uninhabited planet of the system was used as the source of mass for this project. The enterprise was successfully completed within a period of 150 years after receipt of first notice here. Thereafter, naturally, the home star of the Mirt Korp Ahm ceased to be detectible by conventional optical means.”
I pondered the meaning of that set of cloudy phrases without much immediate success. But to Saul Shah-moon the robot’s explanation was lucidity itself. “Of course!” Saul cried. “A Dyson sphere!” Taking no notice of the interruption, Dihn Ruuu sailed serenely onward. “No communications have been received from the home world since the completion of the enclosure project,” the robot said. “However, there is every reason to believe that the Mirt Korp Ahm continue to inhabit their original solar system. Inasmuch as my own responsibilities have been terminated, I propose to journey at once to that system and request reassignment. It would please me if you were to accompany me there.”
Time out for explanations. I needed some myself, at this point.
A Dyson sphere, according to Saul, is a concept first put forth by an American physicist, Freeman Dyson, some time in the early years of the Energy Revolution. Dyson lived in the middle of the twentieth century, after the harnessing of atomic energy but before the colonization of Earth’s surrounding planets.
Dyson’s main point was that in its natural state a solar system is a terribly wasteful thing. The central sun, surrounded by a handful of planets, sends most of its energy shooting uselessly off into space. The planets are too widely separated to intercept more than a small fraction of the energy the sun generates; and therefore the sun’s output speeds away in all directions, radiating so intensely in the visible spectrum alone that its light can be seen thousands of light-years away. This has the esthetic advantage of producing lovely starry nights on distant worlds, but otherwise has little to commend it.
A really thrifty civilization, Dyson said, would catch all of its sun’s energy before it was squandered. One way to do it, he suggested, was to demolish Jupiter and use its mass to build a shell surrounding the sun at approximately the distance of Earth’s orbit from the center of the solar system. Smashing up the biggest planet and rearranging its pieces this way would take a fair amount of energy all by itself: roughly as much as the sun’s total output for eight hundred years. But once the job was finished, the shell would intercept every photon of energy coming from the sun; this could be put to use as an all-purpose power source.
Mankind would cease to live on the Earth, which even in his time was a pretty small and crowded place, and unsatisfactory in terms of application of solar energy, since at any given time half of it is receiving no solar radiation at all. Instead we would take up residence on the inner surface of the artificial sphere. Not only would every point on that surface have full access to sunlight at every moment, but the surface area of the sphere would be about one billion times greater than the surface area of the Earth. Splicing in all the plus factors, we’d find that the sphere could comfortably support a human population of 3 x 1023 individuals, which is to say a good many sextillion or septillion people — work out the exponents yourself. Anyway, it would be a gigantic number. Let’s see: Earth has thirteen billion people now, which is 13 x 109, and things are pretty crowded, and this would be a population increase of 1014, so … It gives you the dizzies, eh?
Dyson thought that any intelligent species would be capable of converting its home world into such a sphere within two or three thousand years after it entered the industrial age. So we ought to be able to do it about 4000 A.D. However, it must be a tougher trick in practice than in theory, if the Mirt Korp Ahm, whom we know were at the stage of galactic travel 1.1 billion years ago, waited until a mere thirteen million years ago to do it. Or did they just not bother to get around to it any earlier?
A Dyson sphere would not, of course, show up on optical telescopes, since all of the sun’s light output is trapped inside the sphere. That explains Dihn Ruuu’s failure to see the star when he looked for it in the sky. Nevertheless, even a Dyson-sphere civilization would be unable to make use of all the energy that was available to it, and would have to get rid of some of it in the form of heat, that is to say, infrared radiation. Dyson suggested that the sphere would have a surface temperature of 200° to 300° K., and would be emitting plentiful radiation in the far infrared wavelengths. This, of course, could be detected easily by outside observers. Dihn Ruuu could stop grieving, then. The home star of his creators had neither burned out nor blown up. It was still there — under wraps, so to speak.
Small surprises eclipse big miracles. Old Paradoxian proverb, just invented by your humble servant. Dihn Ruuu had thrown so much astonishing news at us in a dozen sentences that for a moment, in the excitement of the Dyson-sphere discussion, we forgot to get excited over the real orbit-smasher, which was…
That the High Ones possibly weren’t extinct at all…
And that Dihn Ruuu was inviting us to help him pay a call on them.
Wonders were multiplying too swiftly.
Of course, Dihn Ruuu’s guess that the High Ones were still alive was only a guess. The McBurney IV robots had heard neither beep nor plink from the Mirt Korp Ahm in thirteen million years, and it’s dangerous to think of thirteen million years as anything but a zog of a long time. On the other hand, we were accustomed to thinking of the High Ones as beings buried a billion years in the past; if they had survived until thirteen million years ago, it was a reasonable bet that they still existed. On the third hand —
We did a lot of talking all at once, shouting out theories, disputations, suppositions, postulates, hypotheses, and even some plain old guesses. Nobody could hear anybody else in the uproar, until suddenly one voice cut across all the rest:
“Help!”
We fell silent and looked around.
“Who called for help?” Dr. Schein asked.
“I did,” Pilazinool said in a small voice. “I finally did it.”
He finally had. During our excited outburst, the Shilamakka had given way to his old nervous habit of unfastening hands and feet and limbs, and this time, in a kind of supreme act of self-mutilation, he had contrived to unscrew everything at once, arms and legs. Don’t ask me how. I guess he was simultaneously unscrewing his right arm with his left, and his left with his right; however it happened, he had stripped himself down to a bare torso and was looking piteously at his heap of discarded limbs, unable to start assembling himself again. His expression of bewilderment was so intense that I was afraid something was seriously wrong. But then Dr. Schein began to laugh, and Mirrik snorted, and Kelly picked up one of Pilazinool’s arms and put it in place, whereupon Pilazinool began hastily and in huge embarrassment to get the rest of himself attached.