“Do you have a pen, some paper?” Runyan whispered hoarsely to Danielson. He was scarcely breathing.
Danielson rummaged in her purse and produced a pen and a small airline cocktail napkin she had salvaged on the flight down.
“I only have—” she started to say.
“Fine,” Runyan breathed, grabbing the pen and napkin, “that’ll do.”
He pressed the napkin onto his bare knee and began to scratch symbols and numbers on it, oblivious to the uncertain, dispirited conversation in the room. Danielson was confused by his action, but could feel a new tension radiating from him. She had trouble following the discussion. Even though he was completely ignoring her, she felt partially mesmerized by Runyan’s newly focused intensity. She found this intensity, contrasted with a potential for warm amiability, strangely attractive.
Runyan was uncertain how much time had passed when he finally drew a long breath and let it out slowly. He handed the pen back to Danielson and locked eyes with her for a long moment. Then he stuffed the napkin into a pocket of his shorts and waited for a break in the discussion. At an appropriate point he poked a finger up.
Phillips nodded at him. “Dr. Runyan. You have a thought?”
Runyan lapped his fingers together and leaned forward, forearms on his bare knees. He pressed his thumbs in opposition, looked down at his hands and then up toward Phillips. His terrible conclusion was inescapable. Now he had to lead his colleagues down the same path.
“Let me see if I can speak to what is bothering all of us,” he said slowly and reflectively. “We’ve been unable to account for any extraterrestrial source, natural or artificial. The fact that we’re dealing with something that has a fixed direction in space suggests an origin out there.” He jerked a thumb toward the ceiling. “But the basic phenomenon occurs within the depths of the Earth.” He jabbed a long forefinger toward the floor. “It only comes to the surface periodically.”
Danielson sat tensely on the sofa, partially turned toward Runyan, watching his eyes and mouth as he spoke. The words were neutral enough, but seemed darkly ominous to her, a cold vapor filling the room.
“Incredible as it seems,” Runyan continued, “I think the conclusion we’ve been avoiding is that there is actually something inside the Earth, something moving around through the Earth, triggering seismic waves and tunneling holes as it goes.”
He glanced sideways at Danielson, his eyes crinkled by a faint smile. “I don’t remember whether it was Sherlock Holmes or Nero Wolfe who argued that one should throw out every impossible explanation, and the remaining one, no matter how improbable, must be the truth.” The smile faded. “I’ve done something like that in my own mind and reached a conclusion, but it’s bizarre, and I don’t want to prejudice you with it yet. I’d like you to follow this line of reasoning and see where you think it leads.”
Runyan seemed to be sitting calmly, looking around at his colleagues, but Danielson happened to glance down at his feet. His toes were curled around the end of the thongs, gripping them, pale splotches on the knuckles contrasting with the tanned skin.
Across the room, Isaacs was staring at Runyan, mentally groping, trying to grasp the implications of the scientist’s statements. The quiet was broken by Fletcher who sat up straight in his chair and muttered, “Oh, Jesus.” He swiveled to look at Runyan. The two locked gazes and stared at one another for an extended moment. Then Fletcher broke off and waved a hand inviting Runyan to take the floor.
Runyan stood and made his way slowly to the blackboard, deep in thought. With a habit born of long hours in the classroom, he selected a moderately long piece of chalk from the tray before turning to face his audience.
“Let’s forget the seismic signal itself and concentrate on the derived trajectory for a moment,” he began, unconsciously slipping into a pedagogical tone. He turned to the board and sketched a circle representing the Earth, with a curved arrow above it indicating the direction of rotation. Then he added a straight line beginning a third of the way from the equator to the North Pole. The line passed through the center of the circle and out the opposite side.
Watching the tip of the chalk, Danielson suddenly pictured a stiletto, piercing the Earth. Her shoulders contracted in a brief shiver.
“The source moves like this,” Runyan tapped the line with the chalk, “with a period of eighty minutes and thirty seconds. We can think of the Earth as a sphere of roughly constant density, which produces a certain gravitational potential. An object falling freely in that harmonic potential would oscillate back and forth along a line. To close approximation, the line would point to a fixed direction in space. The period would be eighty some-odd minutes.” He looked at Fletcher, then at Leems. “Essentially the same as that of an Earth-orbiting satellite.”
There were scattered rustlings in the room as a couple more individuals began to see where Runyan’s arguments were leading.
“Now, if we consider the real Earth,” Runyan continued, “there would be some differences. A minor factor would be that the density of the Earth is not constant. An orbiting object would feel a somewhat different gravitational pull than the idealized case I’ve described. That would alter the period of the trajectory somewhat. There could also be precessional effects on the orientation, but all that’s negligible for now.”
He looked around the room, focusing briefly on Danielson. Her stomach tightened as if his gaze were a physical grip. His face was a sharp image against blurred surroundings. She could make out beads of sweat along his hairline.
“The significant feature,” Runyan continued, “is that the path is anything like a free orbit since, as we all know, the Earth resists quite effectively the attempt of any material body to move through it. If I’m on the right track, the orbiting body can’t be ordinary material.”
“Let me get this straight,” said Gantt. “You’re proposing that something is actually orbiting within the Earth?”
“C’mon!” snorted Leems.
“That’s the only picture that makes sense to me,” Runyan replied, his voice tensing at the implied skepticism. He turned to the board and drew heavily, repeatedly, on the line that slashed through the circle. “Back and forth on a line fixed by the inertial frame of the stars, independent of the rotation of the Earth. That’s been one of the strangest features of the story Dr. Danielson has told us.
“The problem,” he continued, “is to identify what the thing could be. It’s apparently slicing through the Earth like the proverbial knife through butter. That seems to call for something significantly denser than the densest parts of the mantle and core, denser than anything occurring naturally on Earth or made in any laboratory.”
“I don’t see where you’re going,” said Leems sceptically. “Are you talking about some superheavy element?”
Runyan glared at him. He could see the answer so clearly. Was Leems being deliberately obtuse?
“In a sense,” he replied, coolly. “My thoughts go to stellar examples, where high densities naturally result from huge gravitational fields.” He glanced at Fletcher who gave a brief nod. “White dwarf matter, which is crushed until atoms blur into one another, exists at densities from a million to a billion grams per cubic centimeter. Neutron star material is even more extreme. Matter is squeezed until atomic nuclei dissolve at densities greater than a hundred trillion grams per cubic centimeter. If you could drop a chunk of either kind of matter on Earth, it would meet virtually no resistance and plunge to the center and pass through to the opposite side as it performed an essentially free orbit.”
“Are you suggesting a neutron star is orbiting inside the Earth?” asked Gantt incredulously.