of the formation, therewere coruscations of little shooting stars, and one-two-three planesdisgustedly descended to lower levels as out of action. Then the singleship shot upward, seemed eagerly to shake itself, plunged back--and thelast ships tried wildly to escape, but each in turn was technically shotdown.
The Mahon jet headed back for its own tiny airfield. Somehow, it lookedas if, had it been a dog, it would be wagging its tail and pantinghappily.
"That one ship," said Lecky blankly, "it defeated the rest?"
"It's got a lot of experience," said the sergeant. "You can't beatexperience."
He led the way into Communications Center. In the room where Betsystood, Howell and Graves had been drawing diagrams at each other to thepoint of obstinacy.
"But don't you see?" insisted Howell angrily. "There can be no sourceother than a future time! You can't send short waves throughthree-dimensional space to a given spot and not have them interceptiblebetween. Anyhow, the Compubs wouldn't work it this way! They wouldn'tput us on guard! And an extra-terrestrial wouldn't pretend to be a humanif he honestly wanted to warn us of danger! He'd tell us the truth!Physically and logically it's impossible for it to be anything but whatit claims to be!"
Graves said doggedly:
"But a broadcast originating in the future is impossible!"
"Nothing," snapped Howell, "that a man can imagine is impossible!"
"Then imagine for me," said Graves, "that in 2180 they read in thehistory books about a terrible danger to the human race back in 1972,which was averted by a warning they sent us. Then, from theirhistory-books, which we wrote for them, they learn how to make atransmitter to broadcast back to us. Then they tell us how to make atransmitter to broadcast ahead to them. They don't invent thetransmitter. We tell them how to make it--via a history book. We don'tinvent it. They tell us--from the history book. Now imagine for me howthat transmitter got invented!"
"You're quibbling," snapped Howell. "You're refusing to face a factbecause you can't explain it. I say face the fact and then ask for anexplanation!"
"Why not ask them," said Graves, "how to make a round square or afive-sided triangle?"
* * * * *
Sergeant Bellews pushed to a spot near Betsy. He put down his now-linkedMahon machines and began to move away some of the recording apparatusfocused on Betsy.
"Hold on there!" said Howell in alarm. "Those are recorders!"
"We'll let 'em record direct," said the sergeant.
* * * * *
Lecky spoke feverishly in support of Bellews. But what he said was, ineffect, a still-marveling description of the possibilities ofMahon-modified machines. They were, he said with ardent enthusiasm, thenext step in the historic process by which successively greater portionsof the cosmos enter into a symbiotic relationship with man. Domesticanimals entered into such a partnership aeons ago. Certain plants--wheatand the like--even became unable to exist without human attention. Andmachines were wrought by man and for a long time served him reluctantly.Pre-Mahon machines were tamed, not domestic. They wore themselves outand destroyed themselves by accidents. But now there were machines whichcould enter into a truly symbiotic relationship with humanity.
"What," demanded Howell, "what in hell are you talking about?"
Lecky checked himself. He smiled abashedly:
"I think," he said humbly, "that I speak of the high destiny of mankind.But the part that applies at the moment is that Sergeant Bellews mustnot be interfered with."
He turned and ardently assisted Sergeant Bellews in making room for thejust-brought devices. Sergeant Bellews led flexible cables from them toBetsy. He inserted their leads in her training-terminals. He madeadjustments within.
It became notable that Betsy's standby light took up new tempos in itswavering. There were elaborate interweavings of rate and degree ofbrightening among the lights of all three instruments. There was nopossible way to explain the fact, but a feeling of pleasure, of zestfulstirring, was somehow expressed by the three machines which had beenlinked together into a cooperating group.
Sergeant Bellews eased himself into a chair.
"Now everything's set," he observed contentedly. "Remember, I ain't seenany of these broadcasts unscrambled. I don't know what it's all about.But we got three Mahon machines set up now to work on the next crazybroadcast that comes in. There's Betsy and these two others. And allmachines work accordin' to the Golden Rule, but Mahon machines--they arehoney-babes! They'll bust themselves tryin' to do what you ask 'em. AndI asked these babies for plenty--only not enough to hurt 'em. Let's seewhat they turn out."
He pulled a pipe and tobacco from his pocket. He filled the pipe. Hesqueezed the side of the bowl and puffed as the tobacco glowed. Herelaxed, underneath the wall-sign which sternly forbade smoking by allmilitary personnel within these premises.
It was nearly three hours--but it could have been hundreds--beforeBetsy's screen lighted abruptly.
* * * * *
The broadcast came in; a new transmission. The picture-pattern onBetsy's screen was obviously not the same as other broadcasts fromnowhere. The chirps and peepings and the rumbling deep sounds were notrepetitions of earlier noise-sequences. It should have taken many daysof finicky work by technicians at the Pentagon before the originallybroadcast picture could be seen and the sound interpreted. But aplay-back recorder named Al, and a picture-unscrambler named Gus were inclosed-circuit relationship with Betsy. She received the broadcast andthey unscrambled the sound and vision parts of it immediately.
The translated broadcast, as Gus and Al presented it, was calculated toput the high brass of the defense forces into a frenzied tizzy. Theanguished consternation of previous occasions would seem like very calmcontemplation by comparison. The high brass of the armed forces shouldgrow dizzy. Top-echelon civilian officials should tend to talkincoherently to themselves, and scientific consultants--biologists inparticular--ought to feel their heads spinning like tops.
The point was that the broadcast had to be taken seriously because itcame from nowhere. There was no faintest indication of any signaloutside of Betsy's sedately gray-painted case. But Betsy was not makingit up. She couldn't. There was a technology involved which required themost earnest consideration of the message carried by it.
And this broadcast explained the danger from which the alleged futurewished to rescue its alleged past. A brisk, completely deracializedbroadcaster appeared on Gus's screen.
In clipped, oddly stressed, but completely intelligible phrases, heexplained that he recognized the paradox his communication represented.Even before 1972, he observed, there had been argument about what wouldhappen if a man could travel in time and happened to go back to anearlier age and kill his grandfather. This communication was aninversion of that paradox. The world of 2180 wished to communicate backin time and save the lives of its great-great-great-grandparents so thatit--the world of 2180--would be born.
Without this warning and the information to be given, at least half thehuman race of 1972 was doomed.
In late 1971 there had been a mutation of a minor strain of_staphylococcus_ somewhere in the Andes. The new mutation thrived andflourished. With the swift transportation of the period, it had spreadpractically all over the world unnoticed, because it produced nosymptoms of disease.
Half the members of the human race were carriers of the harmless mutated_staphylococcus_ now, but it was about to mutate again in accordancewith Gordon's Law (the reference had no meaning in 1972) and the newmutation would be lethal. In effect, one human being in two carried inhis body a semi-virus organization which he continually spread, andwhich very shortly would become deadly. Half the human race was bound todie unless it was instructed as to how to cope with it. Unless--
* * * * *
Unless the world of 2180 told its ancestors what to do about it. Thatwas the proposal. Two-way communication was necessary for the purpose,because th
ere would be questions to be answered, obscure points to beclarified, numerical values to be checked to the highest possible degreeof accuracy.
Therefore, here were diagrams of the transmitter needed to communicatewith future time. Here were enlarged diagrams of individual parts. Theenigmatic parts of the drawing produced a wave-type unknown in 1972. Buta special type of wave was needed to travel beyond the three dimensionsof ordinary space, into the fourth dimension which was time. Thiswave-type produced unpredictable surges of power in the transmitter,wherefore at least six transmitters should be built and linked togetherso that if one ceased operation another would instantly take up thetask.
* * * * *
The broadcast ended