A couple of techs typed on rugged keyboards, booting up the six tappers arranged in a circle around me. Half a billion years ago, these Machines had a sophisticated command interface made from what geoscientists called the ring and the canopy, but now all that was left was the rocky floor. The tappers, invented in the nineteenth century and refined in decades since, were crude, limited versions of what those old interfaces must have been. They looked like low steel tables punctuated by dozens of pistons, now moving up and down in a test pattern. Essentially the tapper was a reconfigurable set of padded hammers—much like those inside a piano—that would bang out a pattern on the rock. That pattern programmed the interface, and the interface would open a stable wormhole between the present and the traveler’s chosen destination in the past. With these humble devices, we manipulated the fabric of the cosmos.
Geoscientists barely understood the Machines better than the first humans to describe them in writing thousands of years ago. Sure, we could control the exit date more precisely than our Bronze Age ancestors. Our tappers could produce complex rhythms that were accurate to the microsecond. So that was progress. We knew each Machine consisted of an interface within the rock, though so far our instruments could not detect anything in the rock other than the expected elements. Then there was a wormhole that came from… somewhere. Sadly, our biggest breakthrough was probably that we understood the Machines’ behavior in the context of geology, rather than magic. Even after thousands of years of using them, we still didn’t know much about how they worked, let alone why.
“Ready when you are.” The tech with red hair and flushed cheeks looked up at me and made a shooing gesture.
I made sure I was at the exact center of the tapper circle, knelt, and put my fists against the rock. There was the thrum of the hammers, their rhythms vibrating my whole body until I couldn’t tell where my skin ended and the Earth began. That’s when the rock softened to liquid. A wet-but-not-wet fluid rose past my hands, then waist, blurring the warehouse walls as it crept past my eyes, enveloping me in a shimmering cylindrical column. It took me a second to adjust to the familiar, uncanny sensation of breathing in water.
Then I sank into the wormhole.
Textbooks say it’s like submerging yourself in a warm bath, but that’s only one sensation. There are many textures as you slide between nanoseconds: fine dust, cool gas, feathery ash. They’re probably all illusions created by the brain in the absence of perception. Or maybe they’re real, for some value of “reality.” There’s a lot of ambiguity in the geosciences. Sometimes people enter the wormhole and never return. We’re left to speculate about whether they stayed deep in the past or were erased in transit. Floating toward my possible death, I always got slightly superstitious. So I had a ritual. I tried to focus on the molecular composition of my thoughts. As long as that skein of sugars, tissues, and electrons functioned, I was still myself. Chemicals pulsed through my brain and I waited.
After minutes or millennia, there was a hazy light ahead, like fire through warped glass. Then solid ground knit itself together beneath me, the liquid drained away, and I could breathe air again. I was in the same position, kneeling, dry except for the place where my knuckles and knees met the salty puddle left by a mostly incomprehensible doorway into spacetime.
The techs in 2022 didn’t look much different from the ones I’d left behind in 1992. Same fieldwork chic: heavy boots, easy-wash pants, and padded canvas jackets with the colorful Flin Flon Time Travel Facility logo embroidered over the right breast. Everyone wore toques. It could get chilly up here, even in summer.
The far end of the hangar was occupied by the same processing office full of battered metal furniture. Inside, a Canadian government official was eating bannock and reading a paperback with swords on the cover. Outside was a line of about fifteen people, waiting for her to check them in or out of the present. I tried to figure out if any of them had come down from the future. Nobody stuck out as particularly anachronistic, and I decided we were all probably in our own present. So far, geologists had only figured out how to make the Machines send us to the past, and it always seemed like most of the traffic here consisted of people going back into history or returning from it.
Once the union-mandated lunch break ended, our queue moved pretty fast. The official looked up when I opened the door. “Identification?”
I raised my shirt to show the identity tattoo, a unique design created by algorithm and drawn partly with fluorescent ink as a half-hearted security measure. The university paid to have it needled into the skin of my left side before I traveled for the first time. Beneath a maze of tangled lines and dots was my date of birth: 1974 C.E. Most people looked exclusively at the date, especially in times before the 1930s. Sure, magistrates and monks in the 400s had heard about our computer-generated codes, but they didn’t have a way to read them. Until somebody figured out how to transport objects through time, or persuaded the masses of another era to build anachronisms at great expense, people were pretty much stuck with the tech of their age.
She swiped a bulky handheld reader over my tattoo, and peered at her monitor. “What was your business in 1992?”
“I’m a geoscientist from UCLA, doing some fieldwork for the Applied Cultural Geology Lab. I was at a concert.”
“What kind of concert?”
“A rock concert, in California. Do you know the band Grape Ape?”
The fan on her computer whined as she typed. “Nope. Was that one of those grunge bands?”
I flashed back to what “grunge” had meant to me when I lived through 1992 for the first time. “No. They’re something different.”
She didn’t bother to ask anything else. I’d been using this Machine for most of my academic career, and there was a long digital record of my comings and goings. No need for further investigation.
Outside the damp hangar, I took a walk through the sprawling Flin Flon Time Travel campus. The air smelled faintly of mown grass, and people were out having lunch at picnic tables dotting the open plazas between buildings that hugged the northern edge of Ross Lake. The campus was deceptively peaceful. All those buildings were teeming with bureaucrats, operatives from vaguely menacing state agencies, travel reps for every possible industry, and quite a few scientific labs.
I caught a shuttle to the airport, rolling past strip malls, housing tracts, and a cavernous Canadian Tire. The city had changed a lot since the late nineteenth century, where I did most of my observation. Back then, Flin Flon was nothing more than a few cuts in the ground surrounded by tents and shacks, a podunk mining town named after an interdimensional traveler from a pulp novel. When prospectors discovered the world’s fifth known Machine, all that changed. Flin Flon was hardly a megacity, but now it was a thriving urban hub on the border between northern Manitoba and Saskatchewan, supporting a steady stream of visitors whose jobs touched the timeline.
Many of those visitors were a captive audience, waiting out their 1,669 days to qualify for travel. All five Machines had limitations, but the hardest to surmount was what travelers called the Long Four Years. Wormholes only opened for people who remained within twenty kilometers of a Machine for at least 1,680 days. The number seemed arbitrary until geologists realized that it was roughly the length of four years during the Cambrian period, half a billion years ago, when the Earth was spinning faster. Cambrian days were roughly three hours shorter than ours, meaning the years were about 417 days long. Any device designed to measure years using a set number of day-night cycles, rather than revolutions around the sun, would wind up with longer and longer “years” as the eons passed.