It dropped like a stone. It fell for long, long seconds. Once it wavered, as if it made a final effort to continue its frenzy in the air. But again it fell like a stone. It reached the horizon. It dropped behind it.
Seconds later the ground trembled very, very slightly. Soames hit the graph-machine case. The pens jiggled. He'd made a time-recording of an earth-shock somewhere.
Now he read off the interval between the burst of screaming static and the jog he'd made by striking the instrument. Earth-shock surface waves travel at four miles per second. The radar had said the thing which appeared in mid-air did so eighty miles away. The static-burst was simultaneous. There was a twenty-second interval between the static and the arrival of the earth-tremor waves. The static and the appearance of something from nowhere and the point of origin of the earth-shock matched up. They were one event. The event was timed with the outburst of radio noise, not the impact of the falling object, which was a minute later.
Soames struggled to imagine what that event could be. The inter-base radio babbled. Somebody discovered that the static had been on all wave-lengths at the same time. Voices argued about it.
In the radar-dome Captain Moggs said indignantly:
"This is monstrous! I shall report this to Washington! What was that thing, Mr. Soames?"
Soames shrugged.
"There isn't anything it could be," he told her. "It was impossible. There couldn't be anything like that."
Gail cocked her head on one side.
"D'you mean it's something new to science?"
Soames realized how much he liked Gail. Too much. So he spoke with great formality. The radar had tried to detect and range on something that wasn't there. The nearest accurate statement would be that the radar had detected something just before it became something the radar could detect, which did not begin to make sense.
Planes didn't appear in mid-sky without previously having been somewhere else; it wasn't a plane. There could be meteors, but it wasn't a meteor because it went too slowly and changed course and stood still in the air and went upward. Nor was it a missile. A ballistic missile couldn't change course, a rocket-missile would show on the radar.
He looked at his watch.
"Six minutes and a half from the static," he said grimly. "Eighty miles. Sound travels a mile every five seconds. Let's listen. Ten seconds—eight—six—four—"
Now the wave-guide radar had gone back to normal operation. Its silver-plated square tube flickered and quivered and spun quickly in this direction and that, searching all the sky.
There was a booming sound. It was infinitely low-pitched. It was long-continued. It was so low in frequency that it seemed more a vibration of the air than a sound.
It died away.
"It's a concussion-wave," said Soames soberly. "It arrived four hundred odd seconds after the static. Eighty miles.... A noise has to be pretty loud to travel so far! A ground-shock has to be rather sharp to be felt as an earth-tremor at eighty miles. Even a spark has to be very, very fierce to mess up radio and radar reception at eighty miles.... Something very remarkable happened down yonder tonight—something somebody ought to look into."
Gail said quickly, "How about a spaceship from another world?"
"It would have come in from outer space," said Soames. "It didn't."
"A secret weapon," said Captain Moggs firmly. "I shall report to Washington and ask orders to investigate."
"I wouldn't," said Soames. "If you ask orders you promise to wait for them. If you wait for orders, whatever fell will be covered by snow past discovery by the time your orders come."
Gail looked at him interestedly, confidently.
"What will you do, then?"
"I think," said Soames, "we'll find it and then report.
"You were planning a cosey little article on Housewives of the Antarctic; The Care and Feeding of One's Penguin Husband. Right?"
Gail grinned suddenly.
"I see. Yes."
"We take off in the 'copter," said Soames. "We start out ostensibly to gather material for an article on Can This Penguin Marriage Be Saved. But we'll be blown off course. We'll find ourselves quite accidentally where the radar said there was the great-grandfather of static bursts, with a ground-shock and a concussion-wave to boot. We may even be blown farther, to where something dived downward for four or five miles and vanished below the horizon."
Captain Moggs said uneasily:
"Most irregular. But it might be wise."
"Of course," said Soames. "It's always safer to report something you've found than not find something you've reported."
"We start at sunrise," said Captain Moggs authoritatively.
Soames went back to the radar. As he looked at it, it picked out something rather smaller than a marble at a height of seventy-nine miles and followed that unthinkably ancient small wanderer of space down to its spectacular suicide by fire at a height of thirty-four miles.
He went painstakingly over the radar. It worked perfectly. The taped record of its observations carried the story of all that Gail and Captain Moggs had seen when he saw it. Machinery may err, but it does not have delusions. It would have to be subject to systematic hallucination to have reported and recorded what this radar insisted was the truth.
When dawn came, he went out to the helicopter's hangar. There was a supply-plane on the runway, but the helicopter belonged at the base. He found himself excessively conscientious in his check-over. Though he hated to admit it, he knew it was because Gail would be in the plane.
When he headed back toward the main building one of the geophysics gang beckoned to him. He followed to the small, far-spaced hut—now snow-buried to its eaves—in which the seismograph ticked away to itself.
"I think I'm going crazy," said the geophysics man. "Did you ever hear of a ground-shock starting inside out?"
He pointed to the graph-paper that fed very, very slowly past the seismograph's pens. The recording did look odd.
"If you put your hand just under the surface of the water in a bathtub," said the geophysics man harassedly, "and jerk it downward, you get a hollow that spreads out with a wave behind it. It's the exact opposite of dropping a pebble into water, which makes a wave that spreads out with a hollow—a trough—behind it. But except for that one way of making it, all waves—absolutely all wave-systems—start out with a crest and a trough behind it. Everywhere, all the time, unless you do what I said in a bathtub."
"I'm a shower man, myself," observed Soames. "But go on."
"This," said the geophysics man bitterly, "is like a bathtub wave. See? The ground was jerked away, and then pushed back. Normal shock-waves push away and then spring back! An ice-crack, a rock-slide, an explosion of any sort, all of them make the same kind of waves! All have compression phases, then rarefaction phases, then compression phases, and so on. What—" his voice was plaintive—"what in hell is this?"
"Are you saying," Soames asked after a moment, "that ordinary earth-tremors record like explosion-waves, but that you'd have to have an implosion to make a record like this?"
"Sure!" said the geophysics man. "But how can you have an implosion that will make an earth-shock? I'm going to have to take this whole damned wabble-bucket apart to find out what's the matter with it! But there's nothing the matter! It registered what it got! But what did it get?"
"An implosion," said Soames. "And if you have trouble imagining that, I'm right there with you."