Harry Turtledove

by The Best Time Travel Stories of the 20th Century

  His assistants pricked up their ears. “Who is it?” asked Barton. “My guess was the Atomic Development Authority.”

  “You may be right,” said the Professor. “At any rate, Henderson and Barnes are in charge.”

  This time the bomb exploded effectively; so much so that Davis nearly drove the jeep off the road—not that that made much difference, the road being what it was.

  “Henderson and Barnes? In this god-forsaken hole?”

  “That’s right,” said the Professor gaily. “The invitation was actually from Barnes. He apologized for not contacting us before, made the usual excuses, and wondered if I could drop in for a chat.”

  “Did he say what they are doing?”

  “No; not a hint.”

  “Barnes and Henderson?” said Barton thoughtfully. “I don’t know much about them except that they’re physicists. What’s their particular racket?”

  “They’re the experts on low-temperature physics,” answered Davis. “Henderson was Director of the Cavendish for years. He wrote a lot of letters to Nature not so long ago. If I remember rightly, they were all about Helium II.”

  Barton, who didn’t like physicists and said so whenever possible, was not impressed. “I don’t even know what Helium II is,” he said smugly. “What’s more, I’m not at all sure that I want to.”

  This was intended for Davis, who had once taken a physics degree in, as he explained, a moment of weakness. The “moment” had lasted for several years before he had drifted into geology by rather devious routes, and he was always harking back to his first love.

  “It’s a form of liquid helium that only exists at a few degrees above absolute zero. It’s got the most extraordinary properties—but, as far as I can see, none of them can explain the presence of two leading physicists in this corner of the globe.”

  They had now arrived at the camp, and Davis brought the jeep to its normal crash-halt in the parking space. He shook his head in annoyance as he bumped into the truck ahead with slightly more violence than usual.

  “These tires are nearly through. Have the new ones come yet?”

  “Arrived in the ’copter this morning, with a despairing note from Andrews hoping that you’d make them last a full fortnight this time.’’

  “Good! I’ll get them fitted this evening.”

  The Professor had been walking a little ahead; now he dropped back to join his assistants.

  “You needn’t have hurried, Jim,” he said glumly. “It’s corned beef again.”

  It would be most unfair to say that Barton and Davis did less work because the Professor was away. They probably worked a good deal harder than usual, since the native laborers required twice as much supervision in the Chief’s absence. But there was no doubt that they managed to find time for a considerable amount of extra talking.

  Ever since they had joined Professor Fowler, the two young geologists had been intrigued by the strange establishment five miles away down the valley. It was clearly a research organization of some type, and Davis had identified the tall stacks of an atomic-power unit. That, of course, gave no clue to the work that was proceeding, but it did indicate its importance. There were still only a few thousand turbo-piles in the world, and they were all reserved for major projects.

  There were dozens of reasons why two great scientists might have hidden themselves in this place: most of the more hazardous atomic research was carried out as far as possible from civilization, and some had been abandoned altogether until laboratories in space could be set up. Yet it seemed odd that this work, whatever it was, should be carried out so close to what had now become the most important center of geological research in the world. It might, of course, be no more than a coincidence; certainly the physicists had never shown any interest in their compatriots near at hand.

  Davis was carefully chipping round one of the great footprints, while Barton was pouring liquid perspex into those already uncovered so that they would be preserved from harm in the transparent plastic. They were working in a somewhat absentminded manner, for each was unconsciously listening for the sound of the jeep. Professor Fowler had promised to collect them when he returned from his visit, for the other vehicles were in use elsewhere and they did not relish a two-mile walk back to camp in the broiling sun. Moreover, they wanted to have any news as soon as possible.

  “How many people,” said Barton suddenly, “do you think they have over there?”

  Davis straightened himself up. “Judging from the buildings, not more than a dozen or so.”

  “Then it might be a private affair, not an ADA project at all.”

  “Perhaps, though it must have pretty considerable backing. Of course, Henderson and Barnes could get that on their reputations alone.”

  “That’s where the physicists score,” said Barton. “They’ve only got to convince some war department that they’re on the track of a new weapon, and they can get a couple of million without any trouble.”

  He spoke with some bitterness; for, like most scientists, he had strong views on this subject. Barton’s views, indeed, were even more definite than usual, for he was a Quaker and had spent the last year of the War arguing with not-unsympathetic tribunals.

  The conversation was interrupted by the roar and clatter of the jeep, and the two men ran over to meet the Professor.

  “Well?” they cried simultaneously.

  Professor Fowler looked at them thoughtfully, his expression giving no hint of what was in his mind. “Had a good day?” he said at last.

  “Come off it, Chief!” protested Davis. “Tell us what you’ve found out.”

  The Professor climbed out of the seat and dusted himself down. “I’m sorry, boys,” he said with some embarrassment, “I can’t tell you a thing, and that’s flat.”

  There were two united wails of protest, but he waved them aside. “I’ve had a very interesting day, but I’ve had to promise not to say anything about it. Even now I don’t know exactly what’s going on, but it’s something pretty revolutionary—as revolutionary, perhaps, as atomic power. But Dr. Henderson is coming over tomorrow; see what you can get out of him.”

  For a moment, both Barton and Davis were so overwhelmed by the sense of anticlimax that neither spoke. Barton was the first to recover. “Well, surely there’s a reason for this sudden interest in our activities?”

  The Professor thought this over for a moment. “Yes; it wasn’t entirely a social call,” he admitted. “They think I may be able to help them. Now, no more questions, unless you want to walk back to camp!”

  ———

  Dr. Henderson arrived on the site in the middle of the afternoon. He was a stout, elderly man, dressed rather incongruously in a dazzling white laboratory smock and very little else. Though the garb was eccentric, it was eminently practical in so hot a climate.

  Davis and Barton were somewhat distant when Professor Fowler introduced them; they still felt that they had been snubbed and were determined that their visitor should understand their feelings. But Henderson was so obviously interested in their work that they soon thawed, and the Professor left them to show him round the excavations while he went to supervise the natives.

  The physicist was greatly impressed by the picture of the world’s remote past that lay exposed before his eyes. For almost an hour the two geologists took him over the workings yard by yard, talking of the creatures who had gone this way and speculating about future discoveries. The track which Professor Fowler was following now lay in a wide trench running away from the main excavation, for he had dropped all other work to investigate it. At its end the trench was no longer continuous: to save time, the Professor had begun to sink pits along the line of the footprints. The last sounding had missed altogether, and further digging had shown that the great reptile had made a sudden change of course.

  “This is the most interesting bit,” said Barton to the slightly wilting physicist. “You remember those earlier places where it had stopped for a moment to have a look aro
und? Well, here it seems to have spotted something and has gone off in a new direction at a run, as you can see from the spacing.”

  “I shouldn’t have thought such a brute could run.”

  “Well, it was probably a pretty clumsy effort, but you can cover quite a bit of ground with a fifteen-foot stride. We’re going to follow it as far as we can. We may even find what it was chasing. I think the Professor has hopes of discovering a trampled battlefield with the bones of the victim still around. That would make everyone sit up.”

  Dr. Henderson smiled. “Thanks to Walt Disney, I can picture the scene rather well.”

  Davis was not very encouraging. “It was probably only the missus banging the dinner gong,” he said. “The most infuriating part of our work is the way everything can peter out when it gets most exciting. The strata have been washed away, or there’s been an earthquake—or, worse still, some silly fool has smashed up the evidence because he didn’t recognize its value.”

  Henderson nodded in agreement. “I can sympathize with you,” he said. “That’s where the physicist has the advantage. He knows he’ll get the answer eventually, if there is one.”

  He paused rather diffidently, as if weighing his words with great care. “It would save you a lot of trouble, wouldn’t it, if you could actually see what took place in the past, without having to infer it by these laborious and uncertain methods. You’ve been a couple of months following these footsteps for a hundred yards, and they may lead nowhere for all your trouble.”

  There was a long silence. Then Barton spoke in a very thoughtful voice.

  “Naturally, Doctor, we’re rather curious about your work,” he began. “Since Professor Fowler won’t tell us anything, we’ve done a good deal of speculating. Do you really mean to say that—”

  The physicist interrupted him rather hastily. “Don’t give it any more thought,” he said. “I was only daydreaming. As for our work, it’s a very long way from completion, but you’ll hear all about it in due course. We’re not secretive—but, like everyone working in a new field, we don’t want to say anything until we’re sure of our ground. Why, if any other palaeontologists came near this place, I bet Professor Fowler would chase them away with a pick-axe!”

  “That’s not quite true,” smiled Davis. “He’d be much more likely to set them to work. But I see your point of view; let’s hope we don’t have to wait too long.”

  ———

  That night, much midnight oil was burned at the main camp. Barton was frankly skeptical, but Davis had already built up an elaborate superstructure of theory around their visitor’s remarks.

  “It would explain so many things,” he said. “First of all, their presence in this place, which otherwise doesn’t make sense at all. We know the ground level here to within an inch for the last hundred million years, and we can date any event with an accuracy of better than one per cent. There’s not a spot on Earth that’s had its past worked out in such detail—it’s the obvious place for an experiment like this!”

  “But do you think it’s even theoretically possible to build a machine that can see into the past?”

  “I can’t imagine how it could be done. But I daren’t say it’s impossible—especially to men like Henderson and Barnes.”

  “Hmmm. Not a very convincing argument. Is there any way we can hope to test it? What about those letters to Nature?”

  “I’ve sent to the College Library; we should have them by the end of the week. There’s always some continuity in a scientist’s work, and they may give us some valuable clues.”

  But at first they were disappointed; indeed, Henderson’s letters only increased the confusion: As Davis had remembered, most of them had been about the extraordinary properties of Helium II.

  “It’s really fantastic stuff,” said Davis. “If a liquid behaved like this at normal temperatures, everyone would go mad. In the first place, it hasn’t any viscosity at all. Sir George Darwin once said that if you had an ocean of Helium II, ships could sail in it without any engines. You’d give them a push at the beginning of their voyage and let them run into buffers on the other side. There’d be one snag, though; long before that happened the stuff would have climbed straight up the hull and the whole outfit would have sunk—gurgle, gurgle, gurgle . . . “

  “Very amusing,” said Barton, “but what the heck has this to do with your precious theory?”

  “Not much,” admitted Davis. “However, there’s more to come. It’s possible to have two streams of Helium II flowing in opposite directions in the same tube—one stream going through the other, as it were.”

  “That must take a bit of explaining; it’s almost as bad as an object moving in two directions at once. I suppose there is an explanation, something to do with Relativity, I bet.”

  Davis was reading carefully. “The explanation,” he said slowly, “is very complicated and I don’t pretend to understand it fully. But it depends on the fact that liquid helium can have negative entropy under certain conditions.”

  “As I never understood what positive entropy is, I’m not much wiser.”

  “Entropy is a measure of the heat distribution of the Universe. At the beginning of time, when all energy was concentrated in the suns, entropy was a minimum. It will reach its maximum when everything’s at a uniform temperature and the Universe is dead. There will still be plenty of heat around, but it won’t be usable.”

  “Whyever not?”

  “Well, all the water in a perfectly flat ocean won’t run a hydro-electric plant—but quite a little lake up in the hills will do the trick. You must have a difference in level.”

  “I get the idea. Now I come to think of it, didn’t someone once call entropy ‘Time’s Arrow’?”

  “Yes—Eddington, I believe. Any kind of clock you care to mention—a pendulum, for instance—might just as easily run forward as backward. But entropy is a strictly one-way affair—it’s always increasing with the passage of time. Hence the expression, ‘Time’s Arrow.’ ”

  “Then negative entropy—my gosh!”

  For a moment the two men looked at each other. Then Barton asked in a rather subdued voice: “What does Henderson say about it?”

  “I’ll quote from his last letter: ‘The discovery of negative entropy introduces quite new and revolutionary conceptions into our picture of the physical world. Some of these will be examined in a further communication.’ ”

  “And are they?”

  “That’s the snag: there’s no ‘further communication.’ From that you can guess two alternatives. First, the Editor of Nature may have declined to publish the letter. I think we can rule that one out. Second, the consequences may have been so revolutionary that Henderson never did write a further report.”

  “Negative entropy—negative time,” mused Barton. “It seems fantastic; yet it might be theoretically possible to build some sort of device that could see into the past. . . .”

  “I know what we’ll do,” said Davis suddenly. “We’ll tackle the Professor about it and watch his reactions. Now I’m going to bed before I get brain fever.”

  That night Davis did not sleep well. He dreamed that he was walking along a road that stretched in both directions as far as the eye could see. He had been walking for miles before he came to the signpost, and when he reached it he found that it was broken and the two arms were revolving idly in the wind. As they turned, he could read the words they carried. One said simply: To the Future; the other: To the Past.

  ———

  They learned nothing from Professor Fowler, which was not surprising; next to the Dean, he was the best poker player in the College. He regarded his slightly fretful assistants with no trace of emotion while Davis trotted out his theory.

  When the young man had finished, he said quietly, “I’m going over again tomorrow, and I’ll tell Henderson about your detective work. Maybe he’ll take pity on you; maybe he’ll tell me a bit more, for that matter. Now let’s go to work.”

  Davis and
Barton found it increasingly difficult to take a great deal of interest in their own work while their minds were filled with the enigma so near at hand. Nevertheless they continued conscientiously, though ever and again they paused to wonder if all their labor might not be in vain. If it were, they would be the first to rejoice. Supposing one could see into the past and watch history unfolding itself, back to the dawn of time! All the great secrets of the past would be revealed: one could watch the coming of life on the Earth, and the whole story of evolution from amoeba to man.

  No; it was too good to be true. Having decided this, they would go back to their digging and scraping for another half-hour until the thought would come: but what if it were true? And then the whole cycle would begin all over again.

  When Professor Fowler returned from his second visit, he was a subdued and obviously shaken man. The only satisfaction his assistants could get from him was the statement that Henderson had listened to their theory and complimented them on their powers of deduction.

  That was all; but in Davis’s eyes it clinched the matter, though Barton was still doubtful. In the weeks that followed, he too began to waver, until at last they were both convinced that the theory was correct. For Professor Fowler was spending more and more of his time with Henderson and Barnes; so much so that they sometimes did not see him for days. He had almost lost interest in the excavations, and had delegated all responsibility to Barton, who was now able to use the big pneumatic drill to his heart’s content.

  They were uncovering several yards of footprints a day, and the spacing showed that the monster had now reached its utmost speed and was advancing in great leaps as if nearing its victim. In a few days they might reveal the evidence of some eon-old tragedy, preserved by a miracle and brought down the ages for the observation of man. Yet all this seemed very unimportant now, for it was clear from the Professor’s hints and his general air of abstraction that the secret research was nearing its climax. He had told them as much, promising that in a very few days, if all went well, their wait would be ended. But beyond that he would say nothing.