Laplace's Mirage

"It's the same principle as the Bayeux Tapestry when you think about it," Martin Diaz mused. "Though, of course, infinitely more complicated."

Nothing is infinitely more than anything else, Julian Glock thought with some asperity. Except infinity itself. (Few things bothered him more than imprecision of thought and expression.) But aloud he merely said, "It's really only a highly accurate three-dimensional camera."

"Infinitely accurate," Diaz retorted (to Glock's irritation). "See?"

"It" was Diaz's Replete Chronophone (TM; pat. pend.), which Glock was examining for its patent application. The two men were sitting at the control board, where three images were displayed on its view screen. The one in the middle showed the two men standing and looking at the machine; on the left, an image of the empty laboratory; on the right, an image of the two men hunched over the control board.

So, three images of the same place, but separated in time. Just like the Bayeux Tapestry. Only, as Glock implied, it was much more like a film strip when you got down to it.

Diaz adjusted some knobs, and the central image expanded to fill the screen. "It captures the field from every possible angle, and absolute accuracy down to the sub-atomic level," he said. "Try it yourself."

That Glock did, and was impressed to see that the inventor was not exaggerating. The Chronophone recorded—and was still recording—the clean, white laboratory in which they sat, and as Glock fiddled with the controls he changed the angle so that he could look down upon himself and Diaz from the ceiling, or up from beneath the legs of the chair on which he sat, or from a corner on the opposite side of the room. As for the "zoom" feature, he pushed it in so close that the fabric of the coat of the man on screen blurred first into a featureless mass, then resolved into wobbling blobs that he recognized as molecules.

"It is also infinitely expandable within the temporal axis," Diaz said. He push a button, and the image shrank, again becoming one of three consecutive images. But at the push of another button, two of the images parted to admit a third between them, which then slid away to admit a fourth, and so on. More and more alike the juxtaposed images grew, and the scale along the bottom indicated that they were closer and closer in time as well, until they were only yocto-seconds apart. And still Diaz zoomed in. Then: "Here, let me show you show you something," he said, and he got up to disappear behind the back of the machine.

Alone, Glock lazily played with the controls, pushing the recording forward in time. He meant only to resynchronize with the present, and it wasn't until the screen showed Diaz re-emerging from behind the machine with a screwdriver in his hand that Glock realized he had—

He swallowed.

He was looking at a recording of the future.

With a pricking astonishment he turned the volume up. "Oh," Diaz's voice floated from the machine's speakers. "You discovered Laplace's mirage."

"Did you say something?" Diaz asked from behind the machine. Glock switched the volume off, but continued to stare, aghast, at the screen.

Diaz stepped out with a screwdriver in his hand. He scrutinized the screen, then chuckled. "Oh," he said, "you discovered Laplace's mirage."

Glock wet his lips. "What is it?"

"You've heard of Laplace, right? Claimed that if he knew the position and movement of every particle in the universe, he could infallibly predict every future state of the system. Well, the Replete Chronophone records the present state of this room with such precision that it can actually extrapolate and show future states."

Glock boggled. "You mean it can see the future?"

Diaz chuckled.

"Well, no. It can only extrapolate future states of the system it records, which is this room. If anything enters the system from outside—basically, if anything comes in through the door," he said, pointing, "that changes the system, and so changes the extrapolated future. Ceteris paribus, yes, it anticipates the future. But ceteris is never paribus. Speaking of which," he said, turning as the door opened.

"Oh, there you are!" his wife exclaimed with a frown as she came in. She glared between the men.

"Mm," Diaz said, and his lips tightened. "What is it?" he asked in a quick, impatient tone.

Glock was too well-bred to eavesdrop, but even with all his attention bent upon the Chronophone he couldn't shut out the sounds of the quarrel that was all too apparently building between them. He was relieved when Diaz pulled his wife behind the partition that hid the guts of the machine. But still their indistinct voices carried.

As he waited, Glock idly pushed the Chronophone forward in time again. Nothing much seemed to be happening in the extrapolated future. He had the sound turned down, so when the screen showed his future self rising and exiting the room, he didn't know what summons it was in answer to. Will I obey it? he wondered. Should I try to resist?

He was staring at the screen some minutes later, with his mouth hanging open in shock, when Diaz called out from behind the partition: "Say, would you mind running those specs I gave you back into town? I forgot to file them for the application, and the deadline's this afternoon." Glock fairly bolted from the room to comply.

He was halfway to town before he thought: If I turn back now, can I stop what the Chronophone showed me?

Can I stop Diaz from seizing his wife by the throat and strangling her with his bare hands?

Yes, he asked himself these questions. But by the time he realized his interference would be an intrusion from outside the system—

—and hence unpredicted by the system, and therefore possible—

—by the clock on his dashboard he saw could never get back in time.