Professor Greenfield searched frantically on the cluttered desk for his ringing phone. Finally he lifted a fallen pile of abstracts and triumphantly snatched it up.

"Hello?"

"Professor Greenfield?" The voice was high pitched and fast. "I did it, Professor! I did it! I've got an experiment that can prove your theory."

Greenfield pulled the phone away from his ear and stared at the display. He didn't recognize the number, or the voice. It sounded like a child.

"Who is this?" asked Greenfield. "Are you one of my graduate students?"

"No!" came the reply. "I'm Billy Martin. I listened to your online advanced physics seminars. All of them. Honest."

Greenfield hesitated. "That's very gratifying, Billy," he said. He glanced out his window at the setting sun. "But I have regular office hours for undergraduate students tomorrow. Why don't you stop by then?"

"Because," said Billy, "my experiment can prove the multiple interacting worlds theory using your gravitational constant differentials hypothesis."

Greenfield stared at his phone again. Billy sounded young. Far too young to contribute to that particular headache of a theory.

"Billy," he said. "Are you in one of my undergraduate classes?"

"No!" Billy's voice rose, sounding even younger than before. "I TOLD you. I listened to your ONLINE lectures."

"So you did." Greenfield rubbed his bald spot. Should he end the call? Something in Billy's voice made him pause instead.

"Why don't you tell me about your experiment?" He leaned back in his chair.

"I got the idea during your lecture on universal particle entanglement," said Billy. "You know, the one where you said that every particle in the universe was entangled to some degree with every other, and went on to--"

"I'm familiar with the lecture," interrupted Greenfield dryly, "considering that I gave it." He glanced at his phone clock. He'd give this one more minute.

"Oh, yeah," said Billy, sounding a little deflated.

"Now, back to your experiment, eh?" prompted Greenfield.

Billy described his experiment, including its equipment, procedure, and hypothesis. Greenfield nodded along.

When Billy began to explain his math, Greenfield straightened up. He switched his phone to speaker, and began typing frantically on his tablet, struggling to keep up.

"Anyway," said Billy, bubbling with excitement, "by leveraging a small amount of energy, we can switch the state of a single particle in our universe so it matches the state of a particle in the nearest adjacent universe, and fractionally change the affected particle's gravitational constant."

Greenfield now sat bolt upright, his phone once more clamped tightly to his ear. He had given up typing and was recording.

"Yes, yes, I begin to see," he said. "And by forcing this change of state in the manner you described, by the laws of entanglement, the new gravitational constant is likewise forced upon every other particle in our universe."

"Yeah!" Billy's voice climbed even higher. "And wouldn't that mean we're in a totally different universe?"

Greenfield's mind was already exploring several new fascinating avenues of inquiry. "It would certainly be different," he said absently.

"Do you think it will be better or worse?" asked Billy.

Greenfield blinked. What was Billy getting at?

"It's not really a matter of better or worse," he said, disconcerted by the question. "Have you considered the actual effects of changing the universal gravitational constant?"

"Oh, sure," said Billy. "That was the first thing I calculated. And don't worry. It will be really small. Less than a thousandth of a percent. We'd never notice it."

"You and I wouldn't," agreed Greenfield, settling back in his chair. "Individual human beings have far too little mass to be substantially affected. But what of the effects on larger objects? Such as this planet? Or, better yet, the sun?"

"Um," said Billy.

"There might be earthquakes," said the professor. "Or the sun could grow hotter and turn most of the Earth into a desert. Or get colder and trigger an ice age."

"I didn't think of all that," Billy admitted, his voice faint.

"It's a lot to think about," said Greenfield. "When you're a little older, why don't you apply to study here, and someday maybe do real experiments in my graduate program."

For several seconds there was no reply.

"Yeah, sure," Billy finally said, his voice flat.

"Excellent," said Greenfield. "Well, good luck until then, Billy."

Satisfied that he had sufficiently encouraged this particular inquiring mind, Greenfield disconnected.

In his darkened bedroom, twelve-year-old Billy sat on the edge of the unmade bed. He dropped his phone onto the dirty sheet beside him. Several ancient desktop computers he'd salvaged and repaired lined the walls of his small room.

The insides of various laser pointers, a microwave oven, high frequency transformers, and other electronic parts glowed and hummed in the center of the floor. A wooden chair tilted back, jammed under the knob of his door.

Billy unclenched his right fist to touch his bruised and blackened eye. His Mom's and her boyfriend's raised, angry voices penetrated up through the floorboards. His left hand clutched a small, gray box with a single switch and an unlit status lamp. A twisted pair of wires trailed from the side of the box and curved down towards the jumble of electronic parts.

As the voices below grew louder, Billy's knuckles tightened on the box.

His mom screamed. There came a loud sharp smack. And her scream cut off.

The sun had set by the time Professor Greenfield left the physics building. Glancing up, he located a few of the brighter stars and the three-quarter moon shining in the night sky.

He hummed to himself and walked briskly along the lighted pathway towards the parking lot. When he reached his car, he opened the door, tossed his tablet inside, and climbed behind the wheel.

He drove off, never noticing how in the clear, cloudless night sky the moon dimmed. Turned orange. Then dark red. And finally disappeared.

But he did notice when the ground began to shake.