In it, I viewed time as a helix (this is, as something like a bedspring). Someone could cut across from one turn directly to the next, thus moving into the future by some exact interval, but being incapable of traveling one day less into the future. (I didn’t know the term at the time, but what I had done was to “quantize” time travel.) 

—In Memory Yet Green, Part I of Asimov’s autobiography

Isaac Asimov, Master Traveller

Even though Asimov’s first story was lost, I find it comforting that the story was about time travel, a theme that he returned to over-and-over again with far more variety than any of his other themes. My favorite Asimov story, given to me by my Grandpa Main in its original 1958 issue of Galaxy will always be “The Ugly Little Boy.”

 ‘Four-dimensional, Mr. Mac? But the fourth dimension is time.’ I had learned that the year before, in the third grade. 

1. The Endochronic Properties of Resublimated Thiotimoline (Mar 1948) Astounding
2. The Micropsychiatric Properties of Thiotimoline (Dec 1953) Astounding
3. Thiotimoline and the Space Age (Oct 1960) Analog
4. Thiotimoline to the Stars (Nov 1973) Analog
5. Antithiotimoline (Dec 1977) Analog

 Mr. Asimov, tell us something about the thermodynamic properties of the compound thiotimoline. 

—Professor Ralph S. Halford to Asimov at the conclusion of his Ph.D. oral exam on May 20, 1948.

 There was a short silence, then he said: “I’ll tell you. Why don’t you check with his students?”
I lifted my eyebrows: “You mean in his classes?”
He seemed annoyed: “No, for Heaven’s sake. His research students! His doctoral candidates!” 

 He lifted his foot to step over a Raggedy Ann doll smiling through its neglect as it lay there in the middle of the walk, a foundling not yet missed. He had not quite put his foot down again . . . 

 Because I built a time machine for myself a couple of years ago and went back to the Mesozoic Era and found out what happened to the dinosaurs. 

 Do you remember the time a few weeks back when all of upper Manhattan and the Bronx were without electricity for twelve hours because of the damndest overload cut-off in the main power board? I won’t say we did that, because I am in no mood to be sued for damages. But I will say this: The electricity went off when my uncle Otton turned the third knob. 

 I did. I needed someone with a universal mind; someone who knew people well enough to be able to live with them centuries way from his own time. Shakespeare was the man. I’ve got his signature. As a memento, you know. 

 He had boarded the kettle in the 575th Century, the base of operations assigned to him two years earlier. At the time the 575th had been the farthest upwhen he had ever traveled. Now he was moving upwhen to the 2456th Century. 

 George was deliriously happy. Two years of red tape and now he was finally back in the past. Now he could complete his paper on the social life of the foot soldier of World War II with some authentic details. 

 Ten years of anything you want, within reason, and then you’re a demon. You’re one of us, with a new name of demonic potency, and many privileges beside. You’ll hardly know you’re damned. 

 An elevator doesn’t involve paradoxes. You can’t move from the fifth floor to the fourth and kill your grandfather as a child. 

 It introduced law to the fourth dimension. 

 He was a very ugly little boy and Edith Fellowes loved him dearly. 

 They’ve put up statues to him, too. The oldest is on the hillside right here where the discovery was made. You can just see it out the window. Yes. Can you make out the inscription? Well, we’re standing at a bad angle. No matter. 

 Yet somehow he knew that all would be well with him. Somehow, as never before, he knew. 

 At any rate, he turned full on me. His lean body shook and his dark eyebrows pulled down over his deep-set eyes as he shrieked at me in a falsetto, “But I’ll never read my obituary. I’ll be deprived even of that.” 

 Your world is a slope and you roll down it all the time. Down and down until you wear out and die. 

 Jack looked at Hornby solemnly. “You invented a time machine, did you?”
   “Long ago.” Hornby smiled amiably and filled his glass again. “Better than the ones those amateurs at Stanford rigged up. I’ve destroyed it, though. Lost interest.” 

 That the first inventor of a workable time machine was a science fiction enthusiast is by no means a coincidence. 

 We can’t be sure how accurate our estimates of time and place are, but you seem to resonate with someone in London in 1871. 

 Time-travel, in the sense of going backward to change reality, is not only technologically impossible now, but it is theoretically impossible altogether. 

 He was a clerk. 

 Of course, but how far can the Sun and Earth move in the few hours it will take us to observe the star? 

 “Because,” and here he struck his chest a resounding thump, “the burning memories of youthful snubs and spurnings remain unavenged and, indeed, forever unavengable.” 

 RG-32 was a rather old-fashioned robot, eminently replaceable. He could observe and report, perhaps without quite the ingenuity and penetration of a human being—but well enough. He would be without fear, intent only on following orders, and he could be expected to tell the truth. 

 He was a very ugly little boy and Edith Fellowes loved him more dearly than anything in the world.