A (me): Since the return is to the exact time of departure, the mass present is constant.
Q: Very well, but what about the arrival in the past? Doesn’t this violate the conservation law?
A: No. The energy needed is taken from the Dirac sea, by the mechanism I explain in detail in the Phys Rev paper. When the object returns to the “future,” the energy is restored to the sea.
Q (intense young physicist): Then doesn’t Heisenberg uncertainty limit the amount of time that can be spent in the past?
A: A good question. The answer is yes, but because we borrow an infinitesimal amount of energy from an infinite number of particles, the amount of time spent in the past can be arbitrarily large. The only limitation is that you must leave the past an instant before you depart from the present.
In half an hour I was scheduled to present the paper that would rank my name with Newton’s and Galileo’s – and Dirac’s. I was twenty-eight years old, the same age that Dirac was when he announced his theory. I was a firebrand, preparing to set the world aflame. I was nervous, rehearsing the speech in my hotel room. I took a swig out of an old Coke that one of my grad students had left sitting on top of the television. The evening news team was babbling on, but I wasn’t listening.
I never delivered that talk. The hotel had already started to burn; my death was already foreordained. Tie neat, I inspected myself in the mirror, then walked to the door. The doorknob was warm. I opened it onto a sheet of fire. Flame burst through the opened door like a ravening dragon. I stumbled backward, staring at the flames in amazed fascination.
Somewhere in the hotel I heard a scream, and all at once I broke free of my spell. I was on the thirtieth story; there was no way out. My thought was for my machine. I rushed across the room and threw open the case holding the time machine. With swift, sure fingers I pulled out the Renselz coils and wrapped them around my body. The carpet had caught on fire, a sheet of flame between me and any possible escape. Holding my breath to avoid suffocation, I punched an entry into the keyboard and dove into time.
I return to that moment again and again. When I hit the final key, the air was already nearly unbreathable with smoke. I had about thirty seconds left to live, then. Over the years I’ve nibbled away my time down to ten seconds or less.
I live on borrowed time. So do we all, perhaps. But I know when and where my debt will fall due.
* * *
Dancer died on February 9, 1969. It was a dim, foggy day. In the morning, he said he had a headache. That was unusual, for Dancer never had headaches. We decided to go for a walk through the fog. It was beautiful, as if we were alone in a strange, formless world. I’d forgotten about his headache altogether, until, looking out across the sea of fog from the park over the bay, he fell over. He was dead before the ambulance came. He died with a secret smile on his face. I’ve never understood that smile. Maybe he was smiling because the pain was gone.
Lisa committed suicide two days later.
You ordinary people, you have the chance to change the future. You can father children, write novels, sign petitions, invent new machines, go to cocktail parties, run for president. You affect the future with everything you do. No matter what I do, I cannot. It is too late for that, for me. My actions are written in flowing water. And having no effect, I have no responsibilities. It makes no difference what I do, not at all.
When I first fled the fire into the past, I tried everything I could to change it. I stopped the arsonist, I argued with mayors, I even went to my own house and told myself not to go to the conference.
But that’s not how time works. No matter what I do, talk to a governor or dynamite the hotel, when I reach that critical moment – the present, my destiny, the moment I left – I vanish from whenever I was, and return to the hotel room, the fire approaching ever closer. I have about ten seconds left. Every time I dive through the Dirac sea, everything I changed in the past vanishes. Sometimes I pretend that the changes I make in the past create new futures, though I know this is not the case. When I return to the present, all the changes are wiped out by the ripples of the converging wave, like erasing a blackboard after a class.
Someday I will return and meet my destiny. But for now, I live in the past. It’s a good life, I suppose. You get used to the fact that nothing you do will ever have any effect on the world. It gives you a feeling of freedom. I’ve been places no one has ever been, seen things no one alive has ever seen. I’ve given up physics, of course. Nothing I discover could endure past that fatal night in Santa Cruz. Maybe some people would continue for the sheer joy of knowledge. For me, the point is missing.
But there are compensations. Whenever I return to the hotel room, nothing is changed but my memories. I am again twenty-eight, again wearing the same three-piece suit, again have the fuzzy taste of stale Cola in my mouth. Every time I return, I use up a little bit of time. One day I will have no time left.
Dancer, too, will never die. I won’t let him. Every time I get to that final February morning, the day he died, I return to 1965, to that perfect day in June. He doesn’t know me, he never knows me. But we meet on that hill, the only two willing to enjoy the day doing nothing. He lies on his back, idly fingering chords on his guitar, blowing bubbles and staring into the clouded blue sky. Later I will introduce him to Lisa. She won’t know us either, but that’s okay. We’ve got plenty of time.
“Time,” I say to Dancer, lying in the park on the hill. “There’s so much time.”
“All the time there is,” he says.
NEEDLE IN A TIMESTACK
Robert Silverberg
Robert Silverberg is an American writer widely known for his science fiction and fantasy stories. He is a many-time winner of the Hugo and Nebula awards, was named to the Science Fiction Hall of Fame in 1999, and in 2004 was designated a Grand Master by the Science Fiction Writers of America. His books and stories have been translated into forty languages. Among his best-known titles are Nightwings, Dying Inside, The Book of Skulls, and the three volumes of the Majipoor Cycle: Lord Valentine’s Castle, Majipoor Chronicles, and Valentine Pontifex. His collected short stories, covering nearly sixty years of work, have been published in nine volumes by Subterranean Press. His attraction to the time travel theme is most notable in his novel-length work in books such as Hawksbill Station, House of Bones, and Up the Line. This story was originally published in Playboy in June of 1983.
Between one moment and the next the taste of cotton came into his mouth, and Mikkelsen knew that Tommy Hambleton had been tinkering with his past again. The cotton-in-the-mouth sensation was the standard tip-off for Mikkelsen. For other people it might be a ringing in the ears, a tremor of the little finger, a tightness in the shoulders. Whatever the symptom, it always meant the same thing: your time-track has been meddled with, your life has been retroactively transformed. It happened all the time. One of the little annoyances of modern life, everyone always said. Generally, the changes didn’t amount to much.
But Tommy Hambleton was out to destroy Mikkelsen’s marriage, or, more accurately, he was determined to unhappen it altogether, and that went beyond Mikkelsen’s limits of tolerance. In something close to panic he phoned home to find out if he still had Janine.
Her lovely features blossomed on the screen – glossy dark hair, elegant cheekbones, cool sardonic eyes. She looked tense and strained, and Mikkelsen knew she had felt the backlash of this latest attempt too.