There was nothing in Lettersthat particularly interested him, but reading it let him pretend to be doing something useful while he was mainly concerned with thawing out and drinking beer. Of course that made the phone ring. There was an old-fashioned voice-only in the bathroom; he leaned over and punched it. “Here.”
“Matty?” Only one person called him that. “Why can’t I see you?”
“No picture, Mother. I’m on the bathroom phone.”
“I’m sending you money so you can have a phone in the bathroom? I wouldn’t mind a phone in the bathroom.”
“It was already here. It would cost extra to take it out.”
“Well, use your cell. I want to see you.”
“No, you don’t. I look like I’ve been up for thirty-six hours. Because I have.”
“What? You’re killing yourself, you know that. Why on Earth would you stay up that long?”
“Lab work.” Actually, he was disinclined to come home to the empty apartment, the empty bed. But he’d never told his mother about Kara. “I’m going to sleep in tomorrow, maybe not even go to the lab.” He kept talking and pushed the HOLD button down for a moment. “Call coming in, Mother. Buzz you tomorrow on the cell.” He hung up and raised the beer to his lips, and there was a perfunctory knock on the apartment door. It creaked open.
He wiped his feet inadequately on the bathroom throw rug and stumbled into the living room. Kara, of course; no one else’s thumb would open the door.
She was pretty bedraggled, pretty andbedraggled, and had a look that Matt had never seen before. Not a friendly look.
“Kara, it’s so good—”
“I finally stopped trying to call you and came over. Where have you beensince yesterday morning?”
“At the lab.”
“Oh, sure. You spent the night at the lab. Forgot to route to your cell. With the secret number even I can’t call.”
“I did! I mean I didn’t.” He spread his arms wide. “I mean I spent the night at the lab and they don’t allow you to route calls there.”
“Look, I don’t care where you spent the night. Really, I don’t care at all. I just need something from the bathroom. Do you mind?”
He stepped aside and she stomped by him, dripping. He followed, also dripping.
She looked in the medicine cabinet and slammed it shut. Then she looked at the tub. “You’re taking a bath in two inches of water?”
“Just, uh, just my feet.”
“Oh, of course, of course, your feet.” She jerked open a drawer. “You’re weird, Matt. Clean feet, though. Here.” She pulled out a baby blue box of Safeluv contraceptive discs. “Don’t ask.” She pointed a finger into his face. “Don’t you dare ask.” Her face was flushed and her eyes were bright with held-back tears.
“I wouldn’t—” She pushed her way past him. “Won’t you just stay for a cup of coffee? It’s so bad out.”
“Someone’s waiting.” She stopped at the door. “You can take my thumb off the door now.” She paused, as if wanting to say something more, and then spun into the hall. The door closed with a quiet click.
2
Matt did know something about time travel,though it wasn’t his specialty. He didn’t really have a specialty, not anymore, though he was only a couple of hard courses and a dissertation away from his doctorate in physics.
Everybody does travel through time toward the future, trivially, one second at a time. There was no paradox involved in going forward even faster—in fact, modern physics had allowed that possibility since Einstein’s day.
Demonstrating that, though—time dilation through relativistic contraction—requires either really high speeds or the ability to measure very small amounts of time. You have the “twin paradox,” where one twin stays at home and the other flies off to Alpha Centauri and back at close to the speed of light. That’s eight light-years, so the traveling twin is about eight years younger when he returns—to him, his stay-at-home brother has traveled forward in time eight years.
They don’t build spaceships that fast, but you can do it on a smaller scale with a pair of accurate clocks. Send one around the world on a jet plane, and when it comes back, the traveling clock will be about a millionth of a second slower than the stay-at-home.
Matt had been familiar with that stuff since before puberty, and then after puberty, the pursuit of physics had exposed him to more sophisticated time-travel models, Gцdel and Tipler and Weyland. But they all required huge deformations of the universe, harnessing black holes and the like.
Not just pushing a button.
Matt woke up on the couch, groggy and aching. Past the row of empty beer cans on the coffee table, an old movie capered on the TV screen. It had been Fellini when he fell asleep. Now it was Lucille Ball with a grating laugh track. He found the remote on the floor and sent her back to the twentieth century.
His feet were cold. He shuffled into the bathroom and stood for a long time under a hot shower.
He still had several days’ worth of clean clothes hanging in the closet, relics of when there used to be a woman living here. Was Kara fanatically folding and hanging for another man now?
The coffee was ready by the time he got dressed. He sweetened a cup with a lot of honey and made a space at the kitchen table by pushing aside some three-day-old newspapers. He brought his bag to the table and took out the machine, still wrapped in the trash-can liner, his notebook, and the piece of graph paper from the professor’s desk.
He plugged in the notebook and scanned the graph paper into it, with the four data points. The first two were guesses, the third approximate, and the fourth timed with a stopwatch. He drew in appropriate error bars with a stylus and asked the notebook to do a Fourier transform on them. As he expected, it gave him a set of low-probability solutions that curved all over the map, but the cleanest one was a straight line with a slope of 11.8—so the next time he pushed the button, the thing should be gone for 24,461 seconds. Six hours and forty-eight minutes, give or take whatever.
Okay, this one would be scientific. He got the digital alarm from his bedroom and set it to show seconds. He put a fresh eight-hour tab into his cell and set it for continuous video, then propped it up on a stack of books so that it stared at the clock and the machine. As an afterthought, he cleared the junk away from the table behind it, and restarted the cell. This would be part of the history of physics. It ought to look neat.
He rummaged through the everything drawer in the kitchen and found his undergraduate multimeter. The calibrator machine’s power source was a Madhya deep-discharge twenty-volt fuel cell, and the multimeter said it was 99.9999 percent charged. He showed the result to the camera. See how much power the thing drew while it was gone.
It was 9:58, so he decided to wait until exactly 10:00 to push the button. Out of curiosity, he pulled a two-dollar coin out of his pocket and set it on top of the machine. That would be his dramatic sound track: the clink of the coin falling when he pushed the button.
His eye on the clock, he could feel his heart racing. What if nothing happened? Well, nobody else would see the tab.
A split second before ten, he jammed his thumb down on the button. The machine dutifully disappeared.
It took the two-dollar coin with it. No clink.
That was interesting. Both he and the coin had been in contact with the machine, but the coin had been on the metal box, not the nonconducting plastic button. What would have happened if it had been him touching the metal instead?
He should have put the cell onthe machine, rather than outside. Get a record of what happens to it when it’s not here. Not here and now.
Well, next time.
Of course the phone rang. He peered at the caller ID. His mother. When it stopped ringing, he called her from the bathroom.