Before Northwood’s horrified sight, he vanished; vanished as though he had turned suddenly to air and floated away. 

 Dear Editor: Thus far the chief objection to time traveling has been this: if a person was sent back into the past or projected into the future, it would be possible for said person to interfere most disastrously with his own birth. —Arthur Berkowitz, 768 Beck Street, Bronx, N.Y. (Mar 1932)

Dear Editor: I write this letter to comment, not on the stories, which satisfy me, but on a few letters in the “Corner” of the March issue; especially Mr. Berkowitz’ letter. . . . Since he brought up the question of the time-traveler interfering disasterously with his own birth, I will discuss it. . . . Back he goes into time and meets his grandfather, before his father’s birth. For some reason John kills his grandfather. —Robert Feeney, 5334 Euclid, Kansas City, Mo. (Jun 1932)

Dear Editor: I read and enjoyed Mr. Feeney’s interesting letter in the June issue, but wish to ask: Why pick on grandfather? . . . This incessant murdering of harmless ancestors must stop. —Donald Allgeier, Mountain Grove, Mo. (Jan 1933) 

 In this, I have even been compelled to manipulate in the matter of time! I must not only defeat and annihilate the minions of Moyen, but must work from a mathematical absurdity, so that at the moment of impact that moment itself must become part of the past, sufficiently remote to remove the monsters at such distance from the earth that not even the might genius of Moyen can return them! 

 The Planck-Bohr quantum theory that the energy of a body cannot vary continuously, but only by a certain finite amount, or exact multiples of this amount, had been the key that unlocked the door. 

Master
   Traveller

 A terrestrial astronomer may reckon that the outburst on Nova Persei occurred a century before the great fire of London, but an astronomer on the Nova may reckon with equal accuracy that the great fire occurred a century before the outburst on the Nova. 

Jack Williamson, Master Traveller

In the 1930s alone, Williamson had five classic time travel stories culminating with “The Legion of Time,” to be followed by what has to be the first of the let’s-kill-Hitler stories and another seven decades of unmatched science fiction.

 Let’s try and reduce it to rationality. The cage was—is, I should ay, since of course it still exists—that cage is a Time-traveling vehicle. It is traveling back and forth through Time, operated by a Robot. 

 I could not help wondering, as we settle swiftly over the city, whether our historians and geologists and other scientists were really right in saying that Denver had at one period been far from the Pacific. 

 “I wish I could remember how that time machine was built and operated,” said Dr. Bird reflectively, as he sat in his private laboratory in the Bureau of Standards some time later, “but Jumor did his work well. I can’t even remember what the thing looked like.” 

 The year of grace 1935! A dull year, a comfortable year! Nothing much happened. The depression was over; people worked steadily at their jobs and forgot that they had every starved; Roosevelt was still President of the United States; Hitler was firmly ensconced in Germany; France talked of security; Japan continued to defend itself against China by swallowing a few more provinces; Russia was about to commence on the third Five Year Plan, to be completed in two years; and, oh, yes—Cuba was still in revolution. 

 I must have a subject. And there is a certain—risk. Not great, now, I’m sure. My apparatus is improved. But, in my first trial, my subject was—injured. I’ve been wondering, Mr. Webb, if you— 

 Past, present, future—all one. And we, moving along the dimension called time, intersect them. I can’t grasp it. But I can’t deny it. If only there were proof— 

 Of course! It has always been known that you would ‘appear’ sooner or later. 

Master
   Traveller

 I’m over the Caroline Islands, longitude 158° 23´ west, latitude 8° 30´ north. There’re millions of people drowning all around me. What shall I do? 

H.L. Gold, Master Traveller

H.L. Gold wrote the earliest story of different eras living side-by-side because of some sort of time storm or, as he called it, an “Inflexure.” But even without that innovation, Gold would deserve an award for the volumes of time travel stories he published as the first Galaxy editor.

Master
   Traveller

 They stand about, little misshapen men with huge heads. But their heads contain only brains. They had machines that could think—but somebody turned them off a long time ago, and no one knew how to start them again. That was the trouble with them. They had wonderful brains. Far better than yours or mine. But it must have been millions of years ago when they were turned off, too, and they just hadn’t thought since then. Kindly little people. 

John W. Campbell, Jr., Master Traveller

Campbell’s three time travel stories were published under his pseudonym of Don Stuart before he took over the reins of Astounding, and even together they would not justify the prestigious Master Traveller Citation. But the number of classic time travel yarns he brought to light at Astounding and Analog make him more than worthy.

 I showed her New York. She’d say, “But why do the people hurry so? Is it really necessary for all those automobiles to keep going and coming? Do the people like to live in layers? If the United States is as big as you say it is, why do you build such high buildings? What is your reason for having so few people rich, so many people poor?” It was like that. And endless. 

 Ah, yes, you have a mathematical means of expression, but no understanding of that time, so it is useless. But the last of humanity was allowed to end before the Sun changed from the original G-O stage—a very, very long time ago. 

 It’s produced another burnt match. Dragged it forward out of the past, sir. There was a burnt match at that spot, until the glass plate moved a few seconds ago. Like the girl and the banana peel, sir. The machine went back to the place where the match had been, and then it went back in time to where the match was, and then it brought it forward. 

 The projected mind, in the body of the organism of the future, would then pose as a member of the race whose outward form it wore, learning as quickly as possible all that could be learned of the chosen age and its massed information and techniques. 

 I can transport you into the past, and you can create events there which never took place in the past we know—but the events are not new. They were ordained from the beginning, if you took that particular path. You are simply embarking upon a different path into a different future, a fixed and preordained future, yet one which will be strange to you because it lies outside your own layer of experience. So you have infinite freedom in all your actions, yet everything you can possibly do is already fixed in time. 

 Incidentally, I have forgotten the most important thing of all. Remember that Donovan’s dominating idea was to prove to me, and to the world, that he had been in the Cretaceous and hobnobbed with its flora and fauna. He was a physicist by inclination, and had the physicist’s flair for ingenious proofs. Before leaving, he loaded a lead cube with three quartz quills of pure radium chloride that he had been using in a previous experiment, and locked the whole thing up in a steel box. 

 In the first revolution it made, the first day it was built, it circled to the ultimate end of time and the universe, and back to the day it was built. 

 There are times, I reflected, when nothing else in the English language is so expressive as the single word, “Nuts.” But I said nothing, hoping that he would work off his enthusiasm by writing a letter to the magazine. I should have known better. 

 I had set up my laboratory in the wilds of the Peak District in Derbyshire, in England, where work could be carried on with the minimum of interference. From this laboratory I had dispatched into the unknown, presumably the future, a multitude of objects, including several live creatures such as rats, mice, pigeons and domestic fowl. In no case could I bring back anything I had made to vanish. Once gone, the subject was gone forever. There was no way of discovering exactly where it had gone. There was nothing but to take a risk and go myself. 

 But Max Planck with the quantum theory, de Broglie and Schroedinger with the wave mechanics, Heisenberg with matrix mechanics, enourmously complicated the structure of the universe—and with it the problem of Time.
With the substitution of waves of probability for concrete particles, the world lines of objects are no longer the fixed and simple paths they once were. Geodesics have an infinite proliferation of possible branches, at the whim of sub-atomic indeterminism.
Still, of course, in large masses the statistical results of the new physics are not much different from those given by the classical laws. But there is a fundamental difference. The apparent reality of the universe is the same—but it rests upon a quicksand of possible change. 

 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.”

Master
   Traveller

 Wah lenksh? Inksh lenksh, coss. Wah you speak? Said, sah-y, daw geh-ih. Daw, neitha. You fresh? Jumm? 

L. Sprague de Camp, Master Traveller

Even before de Camp produced the award winning Lest Darkness Fall, my Grandpa Main had identified him as a Master Traveller based on “Language for Time Travelers,” which was the first of many de Camp essays. Appropriately enough, de Camp’s enjoyable autobiography is titled Time and Chance.

 The Nyandrians are attacking Strofander with shells which traverse not only space, but time as well. 

 He didn’t like to be called the Renegade. 

 History is built event by incident—and each is a brick in its structure. If one small piece should slip— 

—John W. Campbell’s introductory blurb for the story

 Think of the opportunities a time machine offers a newspaper. The other papers can tell them what has happened and what is happening, but, by Godrey, they’ll have to read the Globe to know what is going to happen. 

 I pinched the idea. What makes it madder is that I wasn’t quite sure of what I was stealing, and, crazier still, I don’t know from whence I stole it. 

 The problem of backward-jumping has not hitherto been solved. It involves an obvious paradox. If I go back and slay my own grandfather, what becomes of me? 

 “Now spill it. Just where did you come from?”
   “Geographically,” said Face, “not very far from here. Chronologically, a hell of a long way.” 

 Still, it was odd that the lighting system should have gone on the blink on this first ‘night’ of this first trip of the first spaceship powered by the new, stupendous atomic drive. 

 He could feel the supple firmness of her body even through the folds of her undistended pressure suit. 

 She’d be Hilda Pietjen, daughter of the prime minister, just another chip in the Nazi poker game. And he’d be dead in a bunker, a thousand years before he’d been born. 

1. The Seesaw (Jul 1941) Astounding
2. The Weapon Shops (Dec 1942) Astounding
3. The Weapon Makers (Feb-Apr 1943) Astounding
4. The Weapon Shops of Isher (Feb 1949) Thrilling Wonder Stories

 What did happen to McAllister from the instant that he found the door of the gunshop unlocked? 

 With the new tri-polar units I can deflect the projection field back through time. That’s where I’m going to attack Levin—in his vulnerable past. 

 Most people think of time as a track that they run on from birth to death as inexorably as a train follows its rails—they feel instinctively that time follows a straight line, the past lying behind, the future lying in front. Now I have reason to believe—to know—that time is analogous to a surface rather than a line, and a rolling hilly surface at that. Think of this track we follow over the surface of time as a winding road cut through hills. Every little way the road branches and the branches follow side canyons. At these branches the crucial decisions of your life take place. You can turn right or left into entirely different futures. Occasionally there is a switchback where one can scramble up or down a bank and skip over a few thousand or million years—if you don’t have your eyes so fixed on the road that you miss the short cut. 

 This is a story of something that did—or didn’t—happen. Question is, can it be properly said that it did or did not? 

—Campbell’s introduction to the story

 Wait a minute now—he was under no compulsion. He was sure of that. Everything he did and said was the result of his own free will. Even if he didn’t remember the script, there were some things that he knew “Joe” hadn’t said. “Mary had a little lamb,” for example. He would recite a nursery rhyme and get off this damned repetitive treadmill. He opened his mouth— 

 We are masters of time. We live at the farthest frontier of time itself, and all the ages belong to us. No words could begin to describe the vastness of our empire or the futility of opposing us. 

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

 The technicians would “save” themselves ten years of labor and the new sweeping highway in the future and the past would be open to mankind within the life of its discoverer. 

 Are you not a Man, and do not Men know everything? But I am only a . . . 

Master
   Traveller

 Years ago in one of those American magazines, there was a story of a man who saw himself. He came through a woods somewhere and stumbled on a machine, got in, and it took him three days back in time. Then, he lived forward again, saw himself get in the machine and go back. 

Lester del Rey, Master Traveller

For me, the scope of “My Name Is Legion” might well have garnered del Rey a Master Traveller Citation, but the actual award came when his 1966 juvenile novel, Tunnel Through Time, brought adventure time travel to young readers.

 The German professor had a nice idea for making archeology a branch of Blitzkrieg technique—with the aid of a little tinkering with Time. 

—John W. Campbell’s introduction to the story

 Kenrube was at Gribe Schloss before two P.M., March 21st. This completely nullifies the six P.M. story. Place these scoundrels under arrest, and bring them before me at eight o’clock tonight. 

—comment on a memo from Himmler

 Well, didn’t you realize that this uncertainty holds for the past, too? I hadn’t until Quarrels pointed it out. All we have is a lot of incomplete data. Is it just because we’re stupid? Not at all. We can’t find a unique wave function. 

 Elliot Gallant went back into time thirty years. He liked the peaceful days of yesteryear. He married, had a son. 

 Well, sir, that little machine traveled so fast that before we could stop it we found ourselves in the last century. Somewhere in the 1890s. We were going to drop our oil drip there but I happened to remember that my grandfather was spending his honeymoon in Tokyo sometime during that decade— 

 Yes, they were practically all here, thought Doc Smith, as his gaze moved from one to another of the circle. Williamson, Miller, Hubbard, Bond, McClary, Rocklynne, Heinlein and MacDonald, and many others who had once written about the mysteries of time travel—so many hundreds of years ago now. 

 Stephen frowned. “Before failure of Barrier, we often wondered why we never seed time travelers. We doubted Charnwood’s Law and yet—We decided there beed only two explanations. Either time travel bees impossible, or time travelers cannot be seed or intervene in time they visit.” 

Master
   Travellers

 “Great Snell!” he gasped. “So that was it! I ran into a temporal snag!” 

Henry Kuttner and C.L. Moore, Master Travellers

Kuttner and Moore hold the distinction of being the recipients of the only joint Master Travellers award. It’s hard to pick which is their most unforgetable story: “The Twonky”? “Mimsy...”? “Vintage Season”? Nope. I’m nominating the lesser known “What You Need”!

1. Anachron, Inc. (Oct 1942) Astounding
2. Barrius, Imp. (Jan 1943) Astounding
3. When Is When? (Aug 1943) Astounding

 We can use a limited number of agents for our “foreign” department, but they must be wiry, active, of unusually sound constitution, and familiar with the use of all types of weapons. They MUST be resourceful, of quick decision, tact and of proven courage, as they may be called upon to work in difficult and dangerous situations without guidance or supervision. Previous experience in purchasing or sales work desirable but not necessary. EX-COMMANDO MEN usually do well with us. 

 Time can pass quickly when you are absorbed in your work, but not so quickly as all that. Mr. Partridge looked at his pocket watch. It said nine thirty-one. Suddely, in the space of seconds, the best chronometer available had gained forty-two minutes. 

 “Just grab his right shoulder with that glove, from behind,” SpockPrice was saying. “Press below the collarbone with the points of your fingers, press hard.” 

 He was, Vanning reflected, an odd duck. Galloway was essentially amoral, thoroughly out of place in this too-complicated world. He seemed to watch, with a certain wry amusement, from a vantage point of his own, rather disinterested for the most part. And he made things— 

 Neither Paradine nor Jane guessed how much of an effect the contents of the time machine were having on the kids. 

 I am, sir, a citizen of the world of science. 

 Now, shielding the bills with his body, he took them out for a closer examination. They looked all right. They weren’t counterfeit; the serial numbers were O.K.; and they had the same odd musty smell Holt had noticed before.
“You must have been hoarding these,” he hazarded.
Smith said absently, “They’ve been on exhibit for sixty years—” He caught himself and drank rye. 

 But a time machine is impossible. It is a paradox. Your professors will explain that a time machine cannot be, because it would mean that two things could occupy the same space at the same time. And a man could go back and kill himself when he was younger, and—oh, all sorts of stuff like that. It’s completely impossible. Only a crazy man could— 

 I knew grandfather. He would go as far as his machine could take him. I had duplicated that. He would look around him for a promising site, get out his tools, and pitch in. Well, I could do that, too. 

 We’re here! It’s over, the long night, the incredible journey. We’ll all be waking, seeing each other, as well as the civilization out there. Seeing, too, the great Centauri suns. 

 And now, I realize, Mr. O’Breen, why I was inclined to trust you the moment I saw yoiur card. It was through a fortunately preserved letter of your sister’s, which found its way into our archives, that we knew of the early fiasco of Harrison Partridge and your part therein. We knew, too, of the researches of Dr. Derringer, and how he gave up in despair after his time traveler failed to return, having encountered who knows what unimaginable future barrier. 

 Not that he would necessarily have suspected anyway that he had come into possession of films that had been made more than fifty years in the future. 

 There is that element of wonder, too, you know. Every man in the place knows that someone is going to get clipped with that crane. 

 Looking backward later, Oliver thought that in that moment, for the first time clearly, he began to suspect the truth. But he had no time to ponder it, for after the brief instant of enmity the three people from—elsewhere—began to speak all at once, as if in a belated attempt to cover something they did not want noticed. 

 Bild-a-Man Set #3. This set is intended solely for the use of children, between the ages of eleven and thirteen. The equipment, much more advanced that Bild-a-Man Sets 1 and 2, will enable the child of this age-group to build and assemble complete adult humans in perfect working order. 

 Here; if you can remember the next thirty years, suppose you tell me when the War’s going to end. This one, I mean. 

 I hand him an empty can and say I want it filled with green paint—it should have orange polka dots. 

 Lasker is a mathematician. He specializes in symbolic logic and is the only man I know who can really understand Tarski. 

 Either we live by accident and die by accident, or we live by plan and die by plan. If our lives are written in the Book of Acts, then no effort is worth the candle. For there will be those who will eternally strive to be good and yet shall fail. There will be others who care not nor strive not and yet will thrive. Why? Only because it is so written. And by whom? By the omnipotent God. Who, my friends, has then written into our lives both the good and the evil that we do ourselves! He moves us as pawns, directs us to strive against odds, yet knows that we must fail, because he planned it that way. 

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.

 But searching down time, Troy-Poole now found only the old combination of Troy and Poole he knew so well. Hundreds, thousands, millions of them, each preceding the other. As far back as he could sense, there was always a Poole hovering over a Troy. Now he would become the next Poole, enmesh the next Troy in the web of time, and go his own way to bloody death. 

 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!” 

 Miracle Meal. Press here. 

 Switch is right. It was about time travel. What we call travel through time. So I took the tube numbers he gave me and I put them into the circuit-builder; I set it for ‘series’ and there it is-my time-traveling machine. It travels things through time real good. 

 If Nostradamus would accept the manuscript as being his, the controversy would be ended, and the paraphysicists could extend their mathematics with sureness that led on toward glorious, breathtaking possibilities. Somewhere, perhaps within a few feet, was the man who could settle the question conclusively, and somehow Sidney must find him—and soon! 

 You’re much better off than if we had held the hunt in Sixteenth Century Spain during the inquisition or perhaps ancient Rome during the reign of Caligula. You may even like it here during the brief period of the hunt. It’s a fairly civilized culture, at least in a material sense. 

 Mrat-See turned quickly, wincing at the protest of his aching muscles. The creature standing before him might have issued from a nightmare. Its heavy, barrellike body was slung like a hammock on four bowed legs. The enormous head, with undershot jaw, protruding fangs, and pendulous lips, was turned toward him unswervingly, and the continuing growl was a deep rumble of menace from the massive chest. Mrat-See’s heart leaped with fear. He had seen such creatures before in the Yorkgrad zoo. Dogs they were called. 

 There isn’t going to be anything. It’s all black after tomorrow. 

 Space-time—is cute? 

 Oh, I’m no four-dimensional thinker; but, as I understand it, if people could go back to a more recent time, their actions would affect our own history, which would be a paradox or contradiction of facts. Can’t have that in a well-run universe, you know. 

 Like his colleagues, Aristotle never appreciated the need for constant verification. Thus, though he was married twice, he said that men have more teeth than women. He never thought to ask either of his wives to open her mouth for a count. 

1. Try and Change the Past (Mar 1958) Astounding
2. The Big Time (Mar and Apr 1958) Galaxy
3. Damnation Morning (Aug 1959) Fantastic
4. The Oldest Soldier (May 1960) F&SF
5. No Great Magic (Dec 1963) Galaxy
6. When the Change-Winds Blow (Aug 1964) F&SF
7. Knight’s Move, aka Knight to Move (Dec 1965) Broadside
   
   These might be Changewar, but with no time travel:
8. A Deskful of Girls (Apr 1958) F&SF
9. The Number of the Beast (Dec 1958) Galaxy
10. The Haunted Future, aka Tranquility, or Else! (Nov 1959)    Fantastic
11. The Mind Spider (Nov 1959) Fantastic
12. When the Change-Winds Blow (Aug 1964) F&SF
13. Black Corridor (Dec 1967) Galaxy

 Change one event in the past and you get a brand new future? Erase the conquests of Alexander by nudging a Neolithic pebble? Extirpate America by pulling up a shoot of Sumerian grain? Brother, that isn’t the way it works at all! The space-time continuum’s built of stubborn stuff and change is anything but a chain-reaction. 

—“Try and Change the Past”

 “Time travel is impossible.”
“Why?”
“Why?”
“Yes, why?”
Betty looked to her boss for assistance. None was forthcoming. There ought to be some very quick, positive, definite answer. She said, “Well, for one thing, paradox. Suppose you had a time machine and traveled back a hundred years or so and killed your own great-grandfather. Then how could you ever be born?”
“Confound it if I know,” the little fellow growled. “How?” 

 Ya think I’m stupid? I can see that. 

 “The Alamo, sir.” A slow, steady excitement seemed to burn in the Britainer’s bright eyes. “Santa Anna won’t forget that name, you can be sure. You’ll want to talk to the other officers now, sir? About the message we drew up for Sam Houston?” 

 Also, according to Maulbow, there was a race of the future, human in appearance, with machines to sail the current of time through the universe—to run and tack with the winds of time, dipping in and out of the normspace of distant periods and galaxies as they chose. 

 “Dragons can go between times as well as places. They go as easily to a when as to a where.”
Robinton’s eyes widened as he digested this astonishing news.
“That is how we forestalled the attack on Nerat yesterday morning. We jumped back two hours between times to meet the Threads as they fell.” 

 So what did you do, bring back the results of the Centauri Probe? Kill your grandmother? 

1. The Guy with the Eyes (Feb 1973) Analog
2. The Time-Traveler (Apr 1974) Analog
3. The Law of Conservation of Pain (Dec 1974) Analog
4. Two Heads Are Better Than One (May 1975) Analog
5. Unnatural Causes (Oct 1975) Analog
6. A Voice Is Heard in Ramah . . . (Nov 1975) Analog
7. The Centipede’s Dilemma (1977) in Crosstime Saloon
8. Just Dessert (1977) in Crosstime Saloon
9. The Wonderful Conspiracy (1977) in Crosstime Saloon
10. Dog Day Evening (Oct 1977) Analog
11. Mirror/rorriM off the Wall (Nov 1977) Analog
12. Fivesight (Jul 1979) Omni
13. Have You Heard the One . . .? (Jun 1980) Analog
14. Pyotr’s Story (12 Oct 1981) Analog
15. Involuntary Man’s Laughter (Dec 1983) Analog
16. The Blacksmith’s Tale (Dec 1985) Analog
17. The Mick of Time (May 1986) Analog
18. The Paranoid (from Lady) (Winter 1988) in Pulphouse: Issue Two
19. Callahan’s Lady (1989) 11 connected stories
20. Lady Slings the Booze (1991) aka Kill the Editor
21. The Callahan Touch Mary’s Place book
22. The Immediate Family (Jan 1993) Analog
23. The End of the Painbow (Jul 1993) Analog
24. Off the Wall at Callahan’s 1994
25. Callahan’s Legacy (1996) collection of quotes
26. Post Toast (circa 1996) USENET group alt.callahans
27. Callahan’s Key (2000) new novel
28. Callahan’s Con (2003) new novel
29. Too Hot Too Hoot (from Legacy) (Oct 2006) in This Is My Funniest

 And as Callahan refilled glasses all around, the time traveler told us his story. 

 “Pleasta Meetcha, Bob. Likewise, Sarah. Call me, uh . . .“ The only twentieth-century language in which Three-phasing’s name makes sense is propositional calculus. “ George. George Boole.” 

1. Child of the Sun (Mar 1977) Analog
2. The End of the World    (Jan 1984) Analog
3. Man of the Hour (Oct 1984) Analog
4. Mother of the Year (Apr 1985) Analog
5. Touch of the Match (Feb 1985) Analog
6. Will of the Wisp (May 1985) Analog
7. Crisis! (May 1986) fix-up novel

 But each time you intervene, no matter how subtly, you change the future from which you came. You exist in this time and outside of time and in the future, and so each change makes you forget. 

 Did nobody ever finish one of these, ah, time machines? 

1. Title Publication
2. Floodtide (Nov 1977) in Weird Heroes 8
3. Orion (1984) incorporates “Floodtide”
4. Vengeance of Orion (1988)
5. Orion in the Dying Time (1990)
6. Orion and the Conqueror    (1984)
7. Orion among the Stars (1995)
8. Legendary Heroes (Dec 1996) Dragon Magazine
9. Orion and King Arthur (2012)

 But even from this distance I could see she was the gray-eyed woman I had known in other eras; the woman I had loved, thousands of years in the future of this world. The woman who had loved me. 

—“Floodtide”, reprinted in the March 1983 Analog

  . . . but in all the lines I’m big, tough, and smart enough to know how to take good orders and not hear bad ones. 

 It is possible that the direction in which the associated souls are traveling is always the orientation for which matter becomes more disorganized. 

 I left the American sector of Berlin this morning, April 8, in the year two thousand five and sixty, almost exactly two hundred years in your future. I am indeed a colonel, but not in the Prussian army. I am a colonel in the Neues Schutz-Staffeln—the NSS—an underground paramilitary organization devoted to reuniting West and East Germany. 

 There must be as many different ways in which the world could have got into the state it is now as there are different ways in which it can develop into the future. 

 The past is changeable but self-correcting. Easy to change small things; harder to change big ones. 

 All innocence, she turned to the middle, opened the gatefold, held it out sideways, then vertically. I dropped the beer when she shouted, “Grandma!” 

 “Oh, my God! Tet Offensive!” McGregor stared from one of them to the other. “You’re not telling me that one’s based on fact?” 

 It sounded nice and simple: allow Ben Franklin to invent the laser and let the technology casade. Grow enough so that in five hundred years we’d have something to get us out of this mess. 

 But the beasts my clients hunt on these time safaris are all long extinct anyway. Ending the safaris wouldn’t bring any dinosaurs or mastodons back to life.