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

 They might send someone else, but they might not. The tampering might have already changed things too much. 

 Have you sold a ring recently, in the shape of a serpent with its own tail in its mouth? 

 Most excellent! 

 Oh boy! 

 Harry bought a pair of socks, thick gray wool, for 89 cents. When the man took his dollar, Harry held his breath: each first time made a little pip in his stomach. But on one ever looked at the dates of old bills. He bought two oranges for five cents each, and then, thinking of Manny, bought a third. At a candystore he bought G-8 and His Battle Aces for fifteen cents. At The Collector’s Cozy in the other time they would gladly give him thirty dollars for it. Finally, he bought a cherry Coke for a nickel and headed towards the park. 

 Of course the possible worlds we make don’t compare to the real one we inhabit—not nearly so well furnished, or tricked out with details. And yet still somehow better. More satisfying. Perhaps the novelist is only a special case of a universal desire to reshape, to ‘take this sorry scheme of things entire,’ smash it into bits, and ‘remold it nearer to the heart’s desire’—as old Kyayyám says. The egoist is continually doing it with his own life. To dream of doing it with history is no more useful a game, I suppose, but as a game, it shows more sport. 

 If you build it, they will come. 

 Weirder and weirder, I thought. A Christian Mongol? Living in Byzantium? Talking to me on the space telephone out of the twelfth century? 

 From time to time double checking with the manual, he began to punch in the commands that, he had calculated from ceaseless experimentation, would project him three thousand years into the past, plus of minus fifteen years. It was a vast improvement on his first efforts, which had been accurate only to within two centuries. The reentry program was more precise by orders of magnitude: it would bring him back to the moment of departure, plus zero to seventeen hours. 

1. A Sound of Thunder (11 Aug 1989) dinosaur hunt
2. Touch of Petulance (12 Oct 1990) newspaper from the future
3. The Toynbee Convector (26 Oct 1990)    100 years into the future

 Dinosaurs large and small fill my junkyard workroom. This one given to me by a friend 30 years ago. These given as toys to my daughters, and when they didn’t play with them I simply took them back. So with dinosaurs coming into my life, I often wondered what would happen if I could go back into theirs. Dinosaurs, time machines, put them together and you have a
tale one billion years old. 

—Bradbury’s introduction to “A Sound of Thunder”

 For one thing, paradoxes can occur. Say you build a time machine, go backwards in time and murder your father when he was ten years old. That means you were never born. And if you were never born, how did you build the time machine? Paradox! It's the possibility of wiping out your own existence that makes most people rule out time-travel. Still, why not? If you were careful, you could do it. 

 Well, Papa Smurf, there is one way to get this critter back home, but it’s awfully dangerous. 

 Lieutenant, I’ve got three strange bogeys about a mile north-northwest. They’re like nothing I’ve ever seen before. They don’t even have props. 

 The time-traveling is just too dangerous. Better that I devote myself to study the other great mystery of the universe—women!