certain number of nanoseconds, and then vanished for the same number of nanoseconds after the switch was thrown. And nothing would ever be the same again.
But temporal energy potential had proven to be very resistant to manipulation. Subatomic particles sent back microseconds in time were the limit—and they only tolerated such unnatural treatment for nanoseconds before indignantly snapping back to their proper time. The physicists had heaved a qualified sigh of relief, the philosophers an unqualified one; Weintraub’s discovery, however revolutionary in theory, was clearly devoid of practical applications, including the murder of grandfathers-to-be. Reality still protected itself.
Or so it had seemed for twenty years. Then Mariko Fujiwara had persuaded the by-then aged Weintraub that he had been traveling a dead-end road. Their joint experiments had confirmed her intuition: no energy expenditure could manipulate temporal energy potential to any significant degree; but a tremendous yet finite one, properly applied, could cancel it altogether, breaking the anchor chain, as it were, and setting an object adrift in time. That terrific energy surge sent the object three hundred years into the past before it became controllable. But beyond that it was controllable, and the object, living or otherwise, could be sent to a predetermined temporal point in the past. (Not the future, for temporal energy potential was in an absolute sense nonexistent beyond the constantly advancing wave-front known as “the present.”) There the object would remain until its temporal energy potential was restored—very easy to do, for reasons relating to its already-known stubbornness. A temporal retrieval device that could be so miniaturized as to be easily surgically implantable, and that drew an insignificant amount of energy, sufficed to bring the object back to the location (relative to the planetary gravity field in question) from which it had been displaced, after a total elapsed time identical to that which it had spent in the past.
Neither Weintraub nor Fujiwara had been the kind of sociopath common in the fiction of the twentieth century, when science had first become scary: the “mad scientist” who would pursue his reckless experiments to the bitter end with fanatical if not suicidal perseverance, heedless of the consequences to himself or the world. They had recognized, and been duly terrified by, the mind-numbing potentialities of what they were doing. Moreover, they had been products of a society which had recoiled from the Transhumanist madness just as Europe had once recoiled from the seventeenth century’s savage religious wars into the eighteenth century’s mannered ancien regime. True to the twenty-fourth century’s almost Confucian-like ethos, they had concluded that if reality no longer protected itself, someone else had to—preferably the bureaucratized intellectual elite committed to safeguarding the integrity of the human heritage that had almost been lost.
Thus the Temporal Regulatory Authority had been born. The safest course would have been not to use the Fujiwara-Weintraub Temporal Displacer at all, but the temptation to settle history’s controversies and resolve its mysteries by direct observation had been irresistible. So the Authority had been given exclusive jurisdiction of all extratemporal activity. Its legal monopoly had been confirmed by its possession of the only displacer in existence—an exclusiveness that hardly needed to be legislated, given the installation’s colossal expense and power requirements, which placed it beyond the reach of any private individual or group. And even if some other organization had been able to build and operate such a thing, it could never have done so unnoticed, barring some as-yet-elusive breakthrough.
Then, as experience in time travel had accumulated, two realizations had dawned—the first one staggering in its implications, and the second one seeming to contradict the first.
The first was that the past could be changed.
The second was that reality still protected itself.
“There are no paradoxes,” Jason stated firmly to his new team members. “There are no alternate worlds or branches of time either.”
They sat in a briefing room deep in the Authority’s town-sized installation in Western Australia’s Great Sandy Desert, northwest of Lake Mackay—as far from population centers as it had been possible to put the displacer and its dedicated power plant, lest the latter’s multiply redundant failsafe systems should ever prove inadequate. (As some wag had put it centuries earlier, “Mister Antimatter is not your friend.”) Rutherford was also there, although he had thus far been uncharacteristically laconic, letting Jason conduct the orientation.
“But I don’t understand,” said Dr. Bryan Landry, with the thoughtfully perplexed look that came naturally to his mild, rather broad face. That face was gray-eyed and fairly light complexioned, and his straight hair