Li essa história em uma das muitas antologias que tive ao longo dos anos, mas não consigo encontrá-la. O protagonista é um cientista. Algo dá errado com um experimento e ele começa a pular no tempo. É somente quando ele chega à morte do último humano que o tempo reinicia e ele volta ao presente.
"Vôo para sempre", uma novela de Poul Anderson, que também foi minha resposta (não aceita) para essa velha pergunta. Publicado pela primeira vez em Super Science Stories, Novembro 1950 (disponível no Internet Archive), foi reimpresso várias vezes; algum de estas capas tocar um sino?
A história combina muito bem com a sua descrição, exceto que o protagonista precisa passar da morte do último humano, até da morte de todo o universo, para voltar ao seu tempo. A aventura começa quando o protagonista decide montar sua máquina do tempo nos anos 100 no futuro para descobrir por que as máquinas automáticas não voltaram. (Má ideia.) Ele descobre que uma lei desconhecida da natureza torna impossível viajar mais do que uma curta distância no tempo:
It took two hours to fight back five years. Then Saunders stopped the projector. His voice shook.
"No go, Sam. We've used up three quarters of our stored energy—and the farther back we go, the more we use per year. It seems to be some sort of high-order exponential function."
"So—"
"So we'd never make it. At this rate, our batteries will be dead before we get back another ten years." Saunders looked ill. "It's some effect the theory didn't allow for, some accelerating increase in power requirements the farther back into the past we go. For twenty-year hops or less, the energy increases roughly as the square of the number of years traversed. But it must actually be something like an exponential curve, which starts building up fast and furious beyond a certain point. We haven't enough power left in the batteries!"
Incapaz de voltar, eles começam a "avançar no tempo", esperando encontrar alguma civilização avançada que possa enviá-los de volta.
2500 A.D. The machine blinked into materialization on top of a low hill—the pit had filled in during the intervening centuries. Pale, hurried sunlight flashed through wind-driven rain clouds into the hot interior.
[. . . .]
3100 A.D. A waste of blackened, fused rock. Saunders switched on the Geiger counter and it clattered crazily. Radioactive! Some hellish atomic bomb had wiped Liung-Wei from existence. He leaped another century, shaking.
3200 A.D. The radioactivity was gone, but the desolation remained, a vast vitrified crater under a hot, still sky, dead and lifeless. There was little prospect of walking across it in search of man, not did Saunders want to get far from the machine. If he should be cut off from it. . . .
By 3500, soil had drifted back over the ruined land and a forest was growing. They stood in a drizzling rain and looked around them.
[. . . .]
4100 A.D. They flashed into materialization on a broad grassy sward where low, rounded buildings of something that looked like tinted plastic stood between fountains, statues, and bowers. A small aircraft whispered noiselessly overhead, no sign of motive power on its exterior.
[. . . .]
4300 A.D. The campus buildings were gone, but small, elaborate summerhouses had replaced them. Youths and girls in scanty rainbowhued dress crowded around the machine.
[. . . .]
4400 A.D. A villa was burning, smoke and flame reaching up into the clouded sky. Behind it stood the looming hulk of a ray-scarred spaceship, and around it boiled a vortex of men, huge bearded men in helmets and cuirasses, laughing as they bore out golden loot and struggling captives. The barbarians had come!
Depois de mais algumas paradas, eles chegam ao 50,000 AD, onde grande parte da história acontece no tribunal da Imperatriz Taury.
The four squeezed into the aircraft and it lifted with a groan of ancient engines. Vargor gestured at the fortress ahead and his tone was a little wild. "Welcome to the hold of Brontothor! Welcome to the Galactic Empire!"
"The Empire?"
"Aye, this is the Empire, or what's left of it. A haunted fortress on a frozen ghost world, last fragment of the old Imperium and still trying to pretend that the Galaxy is not dying—that it didn't die millennia ago, that there is something left besides wild beasts howling among the ruins." Vargor's throat caught in a dry sob. "Welcome!"
Eventualmente, em torno do 4,000,000 AD:
He was in a city. But it was not such a city as he had ever seen or imagined, he couldn't follow the wild geometry of the titanic structures that loomed about him and they were never the same. The place throbbed and pulsed with incredible forces, it wavered and blurred in a strangely unreal light. Great devastating energies flashed and roared around him—lightning come to Earth. The air hissed and stung with their booming passage.
The thought was a shout filling his skull, blazing along his nerves, too mighty a thought for his stunned brain to do more than grope after meaning:
CREATURE FROM OUT OF TIME, LEAVE THIS PLACE AT ONCE OR THE FORCES WE USE WILL DESTROY YOU!
Through and through him that mental vision seared, down to the very molecules of his brain, his life lay open to Them in a white flame of incandescence.
Can you help me? he cried to the gods. Can you send me back through time?
MAN, THERE IS NO WAY TO TRAVEL FAR BACKWARD IN TIME, IT IS INHERENTLY IMPOSSIBLE. YOU MUST GO ON TO THE VERY END OF THE UNIVERSE, AND BEYOND THE END, BECAUSE THAT WAY LIES—
He screamed with the pain of unendurably great thought and concept filling his human brain.
GO ON, MAN, GO ON! BUT YOU CANNOT SURVIVE IN THAT MACHINE AS IT IS. I WILL CHANGE IT FOR YOU . . . GO!
The time projector started again by itself. Saunders fell forward into a darkness that roared and flashed.
Saunders continua:
A hundred billion years in the future, the sun had used up its last reserves of nuclear reactions. Saunders looked out on a bare mountain scene, grim as the Moon—but the Moon had long ago fallen back toward its parent world and exploded into a meteoric rain. Earth faced its primary now; its day was as long as its year. Saunders saw part of the sun's huge blood-red disc shining wanly.
So good-by, Sol, he thought. Good-by, and thank you for many million years of warmth and light. Sleep well, old friend.
Some billions of years beyond, there was nothing but the elemental dark. Entropy had reached a maximum, the energy sources were used up, the universe was dead.
The universe was dead!
He screamed with the graveyard terror of it and flung the machine onward. Had it not been for the gods' command, he might have lit it hang there, might have opened the door to airlessness and absolute zero to die. But he had to go on. He had reached the end of all things, but he had to go on. Beyond the end of time—
Finalmente, o universo se reforma e ele volta para casa:
He walked into the living room and smiled at Eve and MacPherson. "Hello," he said. "I guess I must be a little early."