Four knocks. Four knocks would be the sound of victory, opening up time travel to unlimited ranges.
“You ready, Marty McFly?” said Ronald Barth. Harvey Alvarez rolled his eyes, but the nickname was appropriate. Harvey was about to visit the Ronald Barth of seven years ago—albeit through a wall—letting Ron know then that he would succeed making a time machine in the future.
“Ready as I’ll ever be, Doctor Brown.”
Everyone thinks time travel entails crazy dramatic events, like time-loop paradoxes, becoming your own great grandfather, and dinosaur chases, but to Ron there was nothing more exhilarating than a few raps on a wall. Seven years ago, mere days before he installed the first temporal marker, Ron heard knocking from inside the sealed time chamber in his personal lab, well before the university sponsored his work. At the time it stunned him, but he soon realized it had to have been someone on a temporal journey making the noise.
One might expect this to be anti-climactic, since he already knew he was successful, but Ron felt like a victorious general returning home. He had already accomplished time travel. In the last seven years he installed forty-six temporal markers, as many as he could make in that time, and the team had sent time travelers to eleven of them. Ron had gone twice. This time was different.
They calibrated all of the markers, triangulating space and time to send Alvarez to the precise moment of the knocks, before the temporal markers even existed! If they could do it by a few days, it would not be long before they could send the travelers anywhen. Decades ago. Centuries ago. Eons.
The entire team was abuzz around Alvarez strapping himself into the capsule. Dr. Jacobson, the slim, balding professor who headed the program. Dr. Glenn, chubby, black-haired theorist. Dr. Jensen, the quick-witted but flinty physicist who kept her hair in a ponytail. Also Ron and a half dozen interns like Alvarez.
The door closed and the capsule receded into the time machine, which started its cycle.
“Hah,” said Jacobson to Glenn. “I’ll be victorious this round.”
“Howzat?” asked Glenn.
“I changed his instructions to knock three times.”
Ron’s face turned hot and felt like a balloon expanding. “You what?” he roared.
Jacobson jumped into Glenn, who steadied him. “Nothing. I just made it three knocks instead of four.”
“Why? Why in hell would you do that?”
“Well, me and Glenn do this all the time,” Jacobson stammered. “I think we can change the past. He thinks we can’t. So we fix the instructions to see if we can change it.”
“Not after the instructions have been carefully evaluated and approved, you don’t. You can’t run an experiment without approv—” Ron balled his fists on his temples and screeched, stomping in a circle. When he recovered he stuck his finger in Jacobson’s face.
“You stupid, arrogant jerk. Keep your damn rivalries out of my experiments! Don’t you realize what you’ve done? If he comes back after knocking only three times, that means it wasn’t him who I heard seven years ago. We would have failed.”
“Maybe your memory will change,” said Dr. Jacobson, his hands clinging tightly to his tie. “Then we’ll know.”
Ron threw his arms out. “If my memory changes, that means every memory associated with it changes, and we’ll have no idea what really happened.”
Jacobson brightened. “But we’ll know it worked. It will just be three knocks instead of four.”
Ron widened his eyes. “We don’t know how time changes, yet. Time loops may very well be real—have you thought about what happens if the timeline changes and I say three knocks, then you meddle in the new timeline by telling him to knock four times? A time loop of you changing it back and forth between three and four could lock the universe and end it for all eternity. Forever locked by an idiot’s whim.”
“The most dangerous force in the universe,” said Jensen, her beady eyes unmistakably condemning Jacobson.
Ron looked at the time machine’s clock and gasped. “We’ve got less than a minute before he gets back. Quick! What can we do to stop this loop?”
“I’ll concentrate really hard to remember this in the next timeline,” said Jacobson. “I’m the only one that can stop it.”
Glenn shook his head. “You think your brain can overpower time and space?”
“C’mon, Dr. Glenn,” said Ron. “You’re our theorist. What can we do?”
Glenn frowned in thought, then shrugged.
“Can you recalibrate the temporal markers to signal us in the next loop that something changed?” asked Dr. Jensen.
“Almut, that’s genius!” He raced over to the control panel. “I’ll ramp up the—”
The time machine’s engine churned and the door popped open.
“We’re too late.” Ron’s voice a weak rasp.
Harvey Alvarez opened the door of the capsule and unstrapped himself. “You know, we really don’t need these,” he said as he pulled his legs out. He rubbed his forehead and winced.
“Report,” said Ron. He thought he could feel his mind change, memories fading, experiences disappearing. He fought fiercely to keep them.
“Geez,” said Alvarez. “You guys look like you’ve seen a ghost.”
“Report!” they yelled.
“Okay. Geez.” He climbed out and steadied himself on the side. “But someone get me some ice.”
Glenn signaled an intern.
“I arrived. It was pitch black, so I had to grope around for the wall. I knocked three times…” he hesitated. Ron groaned. “Unfortunately, a bolt or something on the floor caught my shoe. You really should build your stuff better, Ron. It twisted me up, and I hit the wall again with my fist. Then I bumped my head on the capsule.” His fingers fidgeted. “I’m really sorry.”
Everyone stared quietly for a few seconds.
Dr. Glenn threw his arms up. “I win again!”