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It could create a time paradox. The results of which could cause a chain reaction that would unravel the very fabric of the space-time continuum and destroy the entire universe!... Granted, that's the worst-case scenario. The destruction however might be limited merely to our own galaxy.
When Marty McFly was fourteen years old, he balked at solving the tensor field Doc put in front of him. The problem wasn't beyond him, but he couldn't solve it while he was distracted by the baseball game. Jack Hanson had thrown a pitch inside and he'd ducked away from it while chopping a defensive half-swing that was nowhere near the ball. His teammates hadn't quite called him a chicken, but they hadn't had to. Marty was fully capable of self-critique.
"Fine, then," Doc had said. "If you don't want to solve it, you don't have to. Am I your physics tutor or your friend?"
The barb had stung. Doc was rarely sarcastic, which made his ironic one-liners hurt all the more because of how they stuck out. Still, he had too much on his mind to add high level mathematics to the list. He fiddled with the ballcap on his head restlessly, strapping and unstrapping the back.
"Other eighth graders don't have to study unified field theory in their spare time. They have time to practice their swings. Why can't I?"
Doc had chuckled derisively. "Don't get ahead of yourself, kiddo. You're not ready for unified field theory. This is just the basic mathematics you need to get out of the way to be prepared for that. UFT isn't until high school. You won't be able to touch the equations I've developed for my flux capacitance theory until you're nearly twenty-five, I'd say, with your doctorate in physics."
"And then we'll be partners, right?"
"Right. Partners and friends. But only if you can solve this tensor field." A week later, having faced down Jack Hanson at the plate and hit an RBI double, Marty finally solved the problem.
***
In nineteen eighty five, Marty McFly went back to nineteen fifty five. He met his mother and father as teenagers, nearly destroyed the time-space continuum, and learned that the flux capacitor required 1.21 gigawatts of power to send the DeLorean back thirty years. These were all clues, but he couldn't even see the whole puzzle.
How had Doc calculated the power to supply the DeLorean? Was that night with Einstein really the first time he had tested the machine? Where was the math that guided the time machine, the math that Doc had taught Marty guided everything in the known world?
When Marty had gotten interested in rock somewhere around his sophomore year of high school, Doc had suspended their UFT seminar to go into the physics of sound. He'd justified it by saying that Marty would need a deep intuitive understanding of waves to follow the flux capacitance equations, but Marty figured it was his way of being a friend. Being supportive of Marty's interests. To thank him, he'd bought Doc a cassette of Leroy Anderson melodies. Soon, the lab was humming to the tune of "The Syncopated Clock", when Marty wasn't borrowing Doc's amps to practice.
Marty used his knowledge of sound engineering to make his band sound better than any of them had dreamed possible, performing on-the-fly Fourier Transforms the like of which Hill Valley had never seen. But the end result was that by the time they went back to learning Unified Field Theory, they were a solid eight months behind Doc's schedule. And by the time Doc was ready to test the DeLorean, Marty was unprepared to serve as more than a glorified lab technician. And friend. Lord knows Doc needed friends.
Time travel had exhilarated and frightened Marty. It was one thing to work on physics problems with Doc Brown, sorting through variables to make them say what you wanted them to. Confronting physics outside of the laboratory was an intersection of two worlds Marty had carefully kept separate. He wasn't a nerd, like those kids who got all the science medals. He was a physicist, an occupation whose training had nothing to do with the lectures he got in high school.
***
Three people had believed Martin McFly would earn his doctorate in physics. Emmett Brown, Tina Benton, and Marty McFly were the only people who had ever believed in his ability as a student. Yet here he was, 29 years old and a hotshot on something besides his skateboard. About to walk across the stage in an outfit nearly as preposterous as the future fashions Doc had once asked him to wear. Except this time it didn't feel preposterous. This time, the clothing fit. Without any servos.
He was the kind of person that people pointed to and said, "He has a bright future ahead of him." His dissertation on "A Discussion of Techniques for the Minimization of Quantum Well Fluctuations in Nanopatterned Materials" was being highly buzzed about, in certain pockets of the scientific community. It was, and there was no point being modest about it, a magnificent compromise between pragmatism and flashing theoretical insight.
He was a little out of place at times in those pockets, but that was acceptable. Doc Brown had taught him that accomplishing valuable scientific research did not require community, merely fellowship. He ignored the snide comparisons to Feynman the way his mentor had ignored the comparisons to Einstein. His work with Dr. Benton had given him purpose and drive. Under her tutelage, he had developed the discipline and attention to detail he could have never gotten from Doc. Still, Dr. Benton was aware of the special relationship he had with the eccentric amateur experimentalist who had taught him physics.
"There were things Doc and I shared that I've never told you about," he had told her when she'd asked. "He knew me better than anyone, and he knew I'd be here some day. But there were things he never shared with me, and I always hoped that if I could reach this point, he'd magically appear and explain how the equations work to me. If there actually were equations."
"What equations?"
"Never mind. Just one of his experiments that I was helping him with. I thought when I completed my studies we would work on it as partners." The equations governing the flux capacitor still eluded him, though he understood what flux was and what a capacitor was. Neither Ohm's Law nor Gauss's Law appeared time-dependent to his careful inspection.
"Pomp and Circumstance" swelled in the background and Marty realized it was time to walk. He pushed thoughts of the time machine aside and turned to join his classmates.
***
That night, Marty had sat down at his desk with a pencil, a notebook, and a fifth of Jack Daniels. This was not his usual regimen by any means, but a sense of desperation and loss had seized him after the graduation party his parents had 'surprised' him with, and he had found he needed to be alone with his work and the bottle.
Neither was this his usual notebook. Borrowing a system from Dr. Benton, all of his research on nanostructures was kept in a series of green bound notebooks. His thesis research had filled seventeen of those notebooks, and he was starting to fill an eighteenth. But his work on time travel was kept in blue notebooks, and it was the sixth blue notebook that he was writing in tonight. The blue notebooks that nobody, not even Dr. Benton, had ever seen.
The tensor field he was working with tonight was the seventh such structure he'd tried, pulling mathematical models from obscure papers by Lorentz, Poincare, and Euler and trying to make them speak to him. Tonight's model was half Einstein and half McFly, the first Frankensteinian monster he'd developed.
It was funny, but the permutations seemed to be coming easier tonight. The liquor sloshed uneasily in his stomach, but his hand was steady. It was almost like he was taking dictation, the symbols coming to him one by one without him investing thought.
Or more like a conversation, him and Doc sitting in the lab trading hypotheses back and forth like friends and partners, the way they were supposed to. The equations he was setting down and the geometries he was describing made sense in a fundamental way they never had before. He recalled his mentor's description of the moment of revelation, the legendary bathroom fall. This drunken night, Marty feels like he's had his own bathroom fall, and is grateful for Doc's ghostly company.
"No, Doc, that doesn't work!" he slurs, unable to see any problem with what he's saying. "If I perform a rotational transform on that matrix, it becomes clear that we end up right where we started. That kind of symmetry could never produce a non-zero flux capacitance!" Except that this time, the equations feel right. The symmetry is something he is stuck with. He's going to have to make it fit.
He doesn't know what makes him say this. Doc was always an experimentalist more than a theoretician, and Dr. Benton has taught him to never accept anything as true until you confirm it in the lab. Twice. To ten significant figures. But this isn't Doc Brown's research now, it's Dr. Martin McFly, and sometimes you just jump on the skateboard and have faith that with your skills and a little luck, it'll take you where you need to go.
He checks over his work again, the numbers fading in and out as he struggles to focus his eyes on the paper. The symmetry is still there, but now he can see the beginnings of a design.
"The flux capacitor," he says, whispering to himself as if afraid somebody is listening. "So that's how you did it, Doc."
Nothing can stop him now, not his fatigued brain telling him to go to sleep and not the laws of physics. He pulls out a T-square and a sheet of 11x17 paper and starts drafting the schematic that will cause the impossible collision.
It seemed so blindingly obvious now. Whenever he traveled in time, it was an altered collision that changed the time stream. His grandfather hitting him instead of his father. Griff punching him instead of his son. Find enough energy to disrupt causality, and direct it in the right direction, and you produce time flux. Build a device to store it and you have a flux capacitor. The time machine was built on altering the time stream.
His pencil point breaks and he debates calling an end to his night. But he's still stuck on that symmetry, the symmetry that originally convinced him he couldn't be right. If the system is that symmetrical, why does it allow this to happen?
He's still stuck on that symmetry. He's still stuck on that symmetry as his head crashes to the table with a surprisingly gentle thud. His last thought before he passes out for the night is that he's maintained more muscle control than he expected.
***
Marty awakens to the smell of fresh instant coffee.
"Hung over from the party?" his mother asks sympathetically, rubbing his shoulders with short, jerky strokes as she sets a cup in front of him. He doesn't tell her that he didn't drink at the party, just nods blearily and accepts the cup of coffee.
The world's granularity is very low at the moment. He cannot be sure that the spoon his mom set in front of him to stir his coffee is not in fact a fork with the tines blurred together. He reaches out and strokes the concavity and is relieved to confirm that it is a spoon. He fumbles the handle into his hand and stirs the coffee absently. When he is convinced it is cool enough, he takes a cautious sip.
Ten minutes later, his stomach is feeling more settled and he is a little more confident that he has sufficient motor skills to speak.
"I think I made a breakthrough last night," he says across the table, where his mom has been patiently reading the Business section of the New York Times. "If I wasn't so drunk that I imagined it." He glances down at his notes and finds that his sketched flux capacitor schematic is still there, though the lines are a lot shakier than he recalled. He slips the cover of the book closed and pushes it aside.
***
Marty's first prototype is less efficient than Doc's. He needs to supply 1.34 GW of power to make the time circuits operate. He borrows the required plutonium from a grad student in the nuclear physics department who owes him a favor. Marty is taking no chances with Libyan terrorists. 88 miles per hour remains the speed required, one of those funny implications of the fine structure constant. So he installs his flux capacitor into a battered Aston Martin a professor friend was trying to unload.
He understands the need for secrecy intuitively, though he doesn't have a mathematical justification for it. He doesn't want another Jennifer incident, let alone a Biff incident. Yet the math seems to be saying there isn't any risk of paradox, and time is self-repairing. The math appears to be telling him that what he saw back in 1955, his photograph fading away as he altered the time stream, is a physical impossibility. The empiricist in him knows there's something he hasn't thought of. The daredevil in him says he'll only figure it out by trying it.
All alone in the night, Marty is not sure if he's more excited about driving a time machine or driving Bond's car. The road is empty clear out to the mountains at this time of a weeknight. When he was younger, he would sometimes take a car out on this road to drag race against a rival, but his manhood doesn't get called into question so often now. He slips the car into gear and starts racing against himself.
The car builds up speed as he moves her smoothly down the straightaway, working the clutch smoothly and carefully but with a measurable degree of satisfaction. The speedometer dial climbs, first into the fifties and then, as the roar of the wind's drag picks up, into the sixties and seventies.
He is breaking the law now, but that's okay. There aren't any police around, and anyway, surely breaking the laws of physics is a more serious offense. He won't be bringing down the physics cops on him, though. By and large, nature is her own enforcer.
Marty tops the 88mph barrier to the familiar crashing sound and then the frightening and peculiar silence of passing instantaneously through time. Then he slams powerfully on the brakes as he looks around to see where has has ended up.
Unlike previous trips, Marty has taken care to travel on a road built by the WPA, a road he knows will still be continuous when he arrives at 8PM July 13, 1942. Doc had never prepared him for that sort of tedious, careful preparation, but his time in Dr. Benton's lab had shown him that if you thought things out before you performed your experiment, you could avoid a lot of disaster.
The road is dusty and potholed, the vibrations passing through the Aston Martin's sporty, tight suspension and making Marty feel alive with that vivid sensation he has been nostalgic for. The ancient Germans called it Wanderlust, the relentless pursuit of new frontiers that has driven the human race farther in each generation than the past generation had imagined possible. The more Marty learns about himself, the more he is sure that it's what drove Doc Brown as well.
"The worst mistake I ever made in my life," he once told an 18 year old Marty McFly, "Was declining to serve my country during the War. I thought I was being so high-minded, refusing to use my gifts to help bring the Atom Bomb to life. 21 year old physics genius Emmett Brown, standing between Roosevelt and the Doomsday Device. When we learned what Adolf Hitler was really doing over in Europe, I regretted it. But it was too late. I was the stuck-up nerd who went to jail instead of answering his country's call to be part of the Greatest Generation. No wonder the whole town hates me."
"I didn't realize they sent scientists to jail for refusing to work on the Manhattan Project," Marty had said.
"Not usually, but General Groves was suspicious of me. My cousin Wernher was working for the Nazis, and he feared I would defect if he didn't put me somewhere he could keep an eye on me."
He had put his hand on Marty's shoulder, a tender, friendly caress. "Kid, you may not think the choices you make at your age matter that much. When you're so young, it seems like it's easy to fix a mistake you made. The world doesn't work like that. You may be paying for the rest of your life for a slip up you make next week."
Beale Air Force Base is a 30 minute drive from the mountains on modern roads. On 1940s California roads, it takes him over an hour and a half to reach the erstwhile Camp Beale. Marty starts wondering where he's going to find a road clean enough to safely hit 88. He shrugs, remembering that his contingency plans allow for him to make it back to 1996 even if he has to build a flux capacitor with vacuum tubes and hitch it to a freight train.
He parks on the side of the road a quarter mile from the base. These bases were designed to keep out German and Japanese spies, not to prevent a traveler from the late 20th century armed with powerful technology. With infrared scanners to tell him if anybody is approaching and a battery powered rotary cutter, breaking through the un-electrified fence proves a minimal challenge.
It takes little more than time and patience to shear through. Marty falls into the machinist's zen state, alert and watching for any sign of resistance, but deeply, deeply relaxed by the powerful, dangerous machine he cradles in his arms. At 1AM July 14th, Marty is on base. He prowls, watchful of patrols, fully in command.
The photocopied base plan is in the coat pocket of his surplussed captain's uniform. Marty pulls it out and carefully unfolds it, fold by fold. The building in front of him, as the plan claimed, appears to be the base jail.
It is a forbidding edifice. Squat, illuminated on the outside by nothing more than a single torch, it has no windows at all. A single, solid steel door mars the uniformity of its brick exterior.
Looking around, Marty finds a small grove of oak trees. It appears to be a good place to hide out and wait for morning. He darts over to make sure nobody sees him. Then he sprawls out on the underbrush, his coat carefully folded and set aside so it won't wrinkle. In a moment, he is asleep.
***
He awakens to the sun in his eyes and an uncontrollable urge to scratch his face. Frantic, he looks around and sees to his dismay that there is poison ivy amidst the plants he has slept in. He slips a mirror from his shoulder bag and examines the blotchy red rash covering his left cheek. Great Scott, the Doc would have said. He shrugs and considers for a moment before deciding to go forward with the plan.
He shrugs the captain's coat back onto his shoulders and spends a minute getting in character. Then he strides out of the grove and walks over to the prison, keeping a brisk march that he hopes looks military.
At the front door, he raps twice, quickly. After a minute, the door whines open. A young, fresh-faced blond private greets him with a salute. He returns it, then pulls a sheaf of papers out of his coat, carefully forged with declassified World War II documents as his guide.
"Captain Martin McFly, Special Division. I need to speak to the scientist you have in the poky. Alone." He glares.
The private gulps. "Uh... Special Division, sir?"
"You don't have a need to know, Private... Anderson. Can I see Emmett Brown or do I have to go to your sergeant?"
"No... uh... sir," he stammered. "Fffollow me." Marty was starting to understand why Biff had always loved being the bully. The private leads him down a long white-halled corridor. He removes a key from his belt and unlocks the door. It squeals open and reveals a row of cells. A man that Marty recognized from photographs as young Emmett Brown is sitting on a bench in the third cell on the right, behind the wide iron bars.
The familiar shock of hair makes Marty smile instantly. He quickly suppresses that smile with a harsh grimace for the benefit of the private, and the other prisoners. His hair was light blonde, long, and unruly, resisting gravity as it had.... or rather, would... for the next fifty years. His cheeks were smooth, flecked with a couple days of boyish stubble. His eyes were brown and sharp, but unfocused. He stared off into the distance, not appearing to notice the no-nonsense captain who had just entered the jail.
"You have a room I can interrogate him in alone, private?"
"Yes, sir." He unlocked the door and ordered Emmett to follow. He ignored the private, not even appearing to notice the order. The private grabbed him by the arm and yanked, pulled him brutally off the bench. Caught unaware, he flew off the bench, inertia keeping him in motion until his head slammed against the bars. Marty winced in sympathy, but kept his response to a dry "That was unnecessary, private." Getting in character was easier than he expected.
Emmett and Marty followed the private down the hallway to another locked room. Emmett's nose was bleeding, so Marty handed him the handkerchief from his pocket. The Doc accepted it gratefully.
Finally, they were alone in the room. Marty dismissed the private without saying a word and carefully locked the door. He sat down across the table from his old friend.
"Emmett, this is going to sound strange. Don't you dare faint on me again. I'm Martin McFly. I am a traveler from the future. I was a friend of yours 50 years from now." Again, the tenses.
"You invented... no. You will invent a time machine in the year 1986. I destroyed the machine after a disastrous series of time paradoxes left future-you stuck in the 19th century. But I later built a new machine and came back to set one thing right that you told me you always regretted."
Emmett processed all of this silently, continuing to stare off into space.
"You told me that the one thing in the world you would fix if you had a chance was your decision to sit in jail for the war instead of serving your country."
Emmett snapped to attention.
"I said what? I said I'd rather help destroy the world than sit here and work on new and interesting physics to help us better understand the world? Preposterous!"
"Look, Doc... Do they still call you Doc back in 1942? Doc, the atom bomb project shortened the war by years and saved countless lives. And it eventually settled into a balance of power that left all countries afraid to use the weapon. In 1996, where I came from, countries are slowly phasing out nuclear weapons from their arsenals."
"You shouldn't be telling me so much about the future! If my calculations are correct, it could cause a chain reaction that would unravel the very fabric of the space-time continuum and destroy the entire universe!"
"Your calculations are correct, Doc. Up to a point. But the universe is resilient. When I went back to your work to build the new time machine, I found some terms in the equation that I didn't understand for a while. But I think they're a restitution coefficient. Time travel destabilizes the cosmos, but the universe will always return to the state it was in originally."
"Great Scott! So that's what that expression was."
"But the reason you regretted it wasn't because of the good the atom bomb did for America. It was the personal damage sitting in prison did to your reputation. You became a recluse, isolated from the scientific community, reviled in your home town. Punks vandalized your home. Oppenheimer became famous and you became a famous crazy."
"Oppenheimer? That commie bastard?" Blood starts dripping from his nose again.
"Aww, jeeze, Doc. Look at you. You're a mess. Your nose is bleeding again. Put that handkerchief back up there." He'd forgotten that going back to save 21 year old Doc would involve dealing with, well, 21 year old Doc. Marty was gaining an appreciation for the stunts Doc had endured from him.
"So we were friends in 1996?"
"Uh... no. You died in 1885, after being trapped back in the past by a broken time machine. I got a message from you saying you were happy, so I went back to 1985 and destroyed the machine. Back then, I thought it was too dangerous to keep playing with."
"Oh." His face fell, as he processed the news of this unsettling death. Doc had never been good at dealing with the temporal nonlinearities his machine had introduced, Marty realized. He had been unable to figure out what the restoration coefficient did because in his observation, causality went one way. But Marty had brought his parents back together after separating them. He had prevented Biff from using the almanac. Fixing the timestream was something that Marty understood.
"I'm sorry, Emmett. I should have worked up to that better. But I'm back here now, and I think this is a chance for us to build our friendship again from scratch. This is another chance for you to live your life. You don't have to make the same mistakes this time. I'll be there to help you this time."
He got up, unlocked the door, and pushed it open a few inches, just enough to peek outside. The private he had bullied was still out there, waiting.
"Private, could you bring me a basin of water? And contact your supervisor. I believe he'll be interested in what Doctor Brown here just told me." The private scurried off to do what he asked. It was fun having subordinates. In a minute, the Private returned with the water and word that Captain Hollison would be there in a few minutes. Mighty curious, too, Marty suspected.
In the meantime, he brought the basin of water into the interrogation room. Taking his handkerchief out of Emmett's hand, he dipped it in the water and started to wipe the blood off of Emmett's face with a gentle touch.
"Are you okay, Emmett?" he asked, and his old friend nodded dumbly as Marty rubbed his hands over his face. It was the first time Marty had touched Emmett in... ten experiential years... and he wanted to keep doing it. But the captain would be here soon and Emmett needed to be ready.
"When the captain comes in, you tell him that you're prepared to serve General Groves. We'll get you out of this prison and then... we'll see what comes next, okay?" Emmett nodded dumbly again. Jesus, he's just a kid, Marty thought for the fifth time.
***
When the war ended in May, 1945, Doctor Emmett Brown and Doctor Martin McFly found jobs in the University of California-Berkeley's physics department. They taught across the hall from each other for years, spreading the joy they took in the natural world's wonders to generations of students, and taking pleasure in each other's company.
When Marty had gone back out of Camp Beale in 1942 to his Aston Martin time machine, he found that it was already half-faded away. He had turned back and hiked to town with a quizzical smile on his face. His theory had been proven out, but the cost was something he would have to live with.
Dr. Benton wouldn't have approved of any of this. Science the Benton way required carefully controlled experiments that left nothing to chance and took no risks. Dr. Benton would never use herself as a lab subject the way he had, the way Doc Brown had taught him to. But ultimately, for all that he'd learned from her, Marty supposed he was more like Doc than he'd realized. He was, it seemed, more comfortable with being trapped in 1942 than he'd expected.
Any time Emmett asked him about the equations for time travel that Marty had mastered, Marty had just smiled and asked, "Am I your physics tutor or your friend?"