Two technologies came together to make the Time Simulator possible. The first was the McGurk Calculator, a quantum probe of incredible power. It could take any sufficiently large group of particles, study their properties down to the quantum level, and tell you any event that ever happened to them for as long as they had existed as matter. It became a valuable tool for forensics, archeology, and numerous other disciplines, but it was limited to whatever you could put in front of it. It could tell you the chemical and physical processes that the matter making up a book, a knife, a building, or a tree had undergone, but it could only give you indications about what other matter might have been part of the object, or interacted with it, in the past. The more of a picture you tried to build, the more into the territory of guesswork you had to veer.

The second was the Omniscope. It had two components. One was the Cloud: eight thousand automated observatories forming a spherical bubble twelve light years across. With such a width, it could focus on objects millions of light years away with multi-point perspective, giving it the ability to study the entire Local Group—three spiral galaxies and every dwarf, cluster, and rogue object between them—in subatomic detail.

But to turn the Cloud’s data into a useful map of any object it observed required the more technically challenging component of the Omniscope: the Computation Ring. This encircled a dwarf star, sitting a little outside the orbit of the innermost planet, an extremely tight-orbiting, airless world that permanently burned on one size and froze on the other. Most of the Ring was given over to collecting energy from the star to feed the computational core, which stayed in the planet’s shadow. On the opposite side of the ring sat a massive counterweight mounted on an arch projecting outward from the star. The counterweight was tuned to offset the mass not only of the computational core but also of the inner planet and the others that orbited beyond the Ring. It subtly moved in and out to stabilize the whole structure, which rotated a little faster than the natural speed for its orbit in order to align with the inner planet.

Processing the data from the Cloud required a non-negligible percentage of an entire star’s energy output, cooled to near-absolute-zero in the shadow of a tortured world. Even running the completed Omniscope at full power, it still took weeks to complete an atomic model of a single planet, or a human-scale model of a solar system.

That’s where Jen Karman and I came in. She had a fascination with the ancient notion of time travel, which I, as a serious physicist, did my best to dispel. She found herself drawn to the long-abandoned idea of time as a dimension, a river we move along through our lives and could theoretically travel in reverse. I tried to explain to her how the science of our age showed that, to be able to revisit a place as it was in the past, you would need to somehow put all of the matter involved back exactly where it had been at that time. There isn’t a complete copy of the universe sitting at every point along some kind of time continuum; there’s one universe of matter, always in the present, constantly moving and changing in space. Time is merely the measurement of that motion and change. Theories to the contrary had been disproved millennia before us.

We had that conversation countless times over the decades. The last time we had it was after I’d started working on the Omniscope team. She’d taken an interest in the McGurk Calculator’s ability to infer the histories of archeological remains. When I described what the Omniscope could do, a realization hit us both at the same time: The two machines, working together, could recreate the past.

That is, they could build a meticulously accurate model of it. The Omniscope could map the entire Local Group down to the subatomic level, and the Calculator could determine any past state of the atoms in that model. It would have enough information to incorporate virtually every atom any object had ever interacted with, minus a tiny proportion of that matter that might have left the Local Group at some time in the past. But there was enough data to infer the mass and behavior of anything no longer around to be detected directly.

The computational requirements, we quickly acknowledged, would be mind-boggling. We worked for weeks, driven by sheer excitement, to draw up plans for the Time Simulator. The result was a spherical mesh structure that would completely enclose a star, capturing around 15 percent of its total energy output.

The next stage was years of finding backing. The prospect of being able to revisit and observe any point in history excited a lot of powerful and wealthy people, but many baulked at the cost and complexity of building the sphere. A few stayed interested long enough to hear what kind of star it would need to be built around: a giant thousands of times larger than the dwarf around which the Omniscope’s Ring orbited. Only two backers stayed with us past that point, but thankfully, between them, they had the resources we needed.

After that came decades of construction. Three entire planets—dead rocks between half and double the diameter of Earth—had to be fully imaged by the Omniscope before we could start disassembling them. A good portion of the first went toward building the construction rig that would build the actual sphere. Then came the manufacture of each thousand-kilometer collector beam and its attachment to growing meshes on each side of the star.

Around a century after our initial conversation, one of the brightest stars in the Orion Arm began to dim. The Eternity Sphere was taking form.

It’s impossible to truly convey the insanity of standing on the central nexus of the Eternity Sphere. Above you was open space. Around you was the surface of the structure, stretching over a billion kilometers in any direction. Below you was the seething mass of a star hundreds of times larger than the Sun. Looking down into it was only possible with extreme shielding, and even then, more filtering was required to turn the blinding light into a sensible image of the blue star. Once you could look at it, what you saw was an endless ocean of energy. Watching it writhe, churn, and swell made you feel the raw scale and power of creation. But that wasn’t what we were here to do. We did recoup a little expenditure by hosting an expedition whose primary mission was studying the star beneath us, and they occupied a counterweight nexus on the opposite side of the sphere.

Our mission, however, was a mission through time, as much as that could ever be possible. In the months leading up to switch-on day, Jen and I debated where we would go on our first adventure into history. Earth was an obvious place to start; Omniscope models already existed of much of the Solar System, so we’d mostly be testing the Simulator’s capacity to analyze that incredible volume of data, and to plug in the gaps. Plus, we both had countless periods of Earth’s history that we wanted to explore.

There were ethical concerns still to be worked out around studying human history, so we went further back. Paleontology had come a long way by then—we had a pretty solid idea of the story of life from the Cambrian onwards on a million-year scale. But there were two aspects of prehistory that needed more exploring: the pre-Cambrian era and the smaller-scale history of certain major events. I agitated for the first, but Jen convinced me to start with the second. More recent events, she argued, should be less challenging to reconstruct, and it made more sense to test the Simulator on a specific point rather than a mission to try and map millions of years of time.

Switch-on day finally arrived 147 years after we first devised our plans for the Simulator. It ran for five weeks. At the end of those weeks, we stood in the colossal holography chamber, an indoor space large enough to simulate an entire country, and watched the picture gradually assemble before our eyes.

Black clouds boiled above our heads. From the cliff on which we stood, an ocean stretched out before us, but it too was black. Not because of the darkness—enough foggy daylight was getting through the clouds for us to see the water. The water itself was black, stained with ash.

“When are we?” Jen asked.

I called up a data projection on my ocular display. “Modelling suggests that the impact was 19,312 years ago,” I said to Jen.

“Did we come too late?” she asked me back. “How can anything be living in this?”

I interrogated the display some more. “There’s some dormant plant life in the soil here. Fungi too, and some insectoids, but that’s all. The sea is virtually lifeless.”

“Sheesh,” she sighed.

“I don’t think it’s a matter of when we are,” I offered, “so much as where.” She looked up, so I went on. “We’re 32 degrees south, and this latitude is pretty much encircled with ejecta right now. But there’s a lot more exposure to sunlight further south.”

“Then what are we waiting for?”

I sent some neural instructions to the simulator, and after a whoosh of dizzying motion, we found ourselves on a snow-covered plain. The clouds above were grey now, visibly darker one way and lighter the other.

“Are we at the pole?” Jen asked.

“No,” I answered, “we’re still at 71 degrees. Global temperatures have crashed outside of the equatorial band. South of here is too cold to bear. North of here is too poisoned to survive. We’re in the closest thing to a habitable zone this planet has right now.”

Jen drew breath as though to speak, then hesitated. I knew what she was too anxious to ask, so I checked the display again. I found what she was hoping for. A quick instruction whisked us a few kilometers to the east, and Jen and I found ourselves face to face with something we thought we’d only ever dream of seeing.

He was standing on the plain, desperately probing the snow for any sign of living plant life, his four legs visibly weak from malnutrition but still bulky nonetheless. A small tail hung behind him, while in front of his ribbed body was a proud head adorned with three horns and a shield-like crest above his face.

Jen involuntarily took a step back.

“He can’t see us,” I joked. She scoffed at me, keeping all her attention on the triceratops. Even though he was a simulation, he was a real individual, looking, living, and acting exactly as he had in his lifetime.

“Nearly twenty thousand years after the impact, he’s still here,” she said in an airy, awestruck voice.

“Him and a few others,” I said, looking at the constantly updating readouts on my ocular display. “Don’t ask me about any particular species yet, but there are still a few million large animals dotted around right now.”

“Not enough to survive,” Jen answered.

“No,” I responded, “but they made it longer than we thought.”

All we wanted to do in that moment was walk through time, stepping forward a few thousand years here and there, until we found the last true dinosaur on Earth, then keep going until we saw life bounce back in the millions of years that were to follow. We wanted to map that story down to the decade. But even with the power of the Simulator, that would take years to model. For now, we contented ourselves with two weeks of exploring this dying world, recording and experiencing all the life that still occupied it, as well as the climate effects of the disaster that had struck a hundred thousand years ago. The adventure was sad at times, but riveting as well.

While we were doing it, the Simulator’s monumental engines followed the instructions we had left and turned themselves to a random day more than four billion years earlier.

We had barely scratched the surface of what the Simulator could do. Today, nearly a half-millennium later, we’re still scratching the surface of what a galaxy full of them can do. The things we’ve learned from our explorations in that time have turbo-charged human progress. The places we can go, the things we can see, the knowledge of reality and of our place in the universe that we now possess makes our lives before seem like a childhood lived in a cave.

We wanted to walk in time. Today, thanks to our efforts, we can walk between galaxies in the company of minds older than the planet we once called home.

Did you enjoy this story? I plan to publish and promote more original fiction via my new magazine, The Endeavourist. Stay up to date with my work by subscribing below.

The Endeavourist

A bi-monthly magazine for curious minds.

By Thomas F. Walker

Mixing comedy and science fiction is a risky business. It can occasionally produce gold, such as the near-universally admired Galaxy Quest, but more often, it produces highly divisive results such as Star Trek: Lower Decks and Hyperdrive. Even well-regarded sci-fi comedies, such as Red Dwarf and The Orville, have seasons that many regard as less success…

Read more

Watching your favorite TV show is great fun, but if you admire the show because it embodies principles you hold dear, watching it can also be a great way to remind yourself of the values and ideas that you want to embody in your own life.

For me, that show is Stargate SG-1. It embodies many of the values that I strive to express in my choices and that I …

Read more

Time travel, as a premise, can enable some fascinating stories and situations that would be otherwise impossible. Consider, for example, The Doctor and Donna Noble arguing about the morality of altering history by saving a man from the eruption of Vesuvius in Doctor Who’s “The Fires of Pompeii.” Or consider Marty McFly introducing 1950s kids to rock mus…

Read more

“How should I know?”

That was Joanna’s answer to everything. Young Bradley Brown, sitting in the back of the car, his school backpack slung over one arm, briefly felt frustrated at the dismissive response. But his mind quickly returned to the question he’d asked: How it was that the back wheels of the car went round corners without one of them slipping, …

Read more

We’re going to stumble, make mistakes, I’m sure more than a few before we find our footing, but we’re going to learn from those mistakes. That’s what being human is all about. —Captain Jonathan Archer, “Star Trek: Enterprise—Shockwave: Part 2” (2002)

Star Trek has always stood out from other TV and film franchises because of its optimism. From the first …

Read more

Author’s note: This article contains spoilers for the shows and video games discussed. I have tried to keep these to a minimum.

What valuable ideas can we gain from comparing sci-fi’s dogmatic religious villains?

Science fiction naturally appeals to people with curious, scientific, and reason-oriented worldviews, and its heroes—from James T. Kirk and John…

Read more

In the first half of 2026, two major space-based movies have hit cinemas. The first was an exceptionally good adaptation of Andy Weir’s novel Hail Mary. The second—and the only major release to be an original story—is The Mandalorian and Grogu, and it’s a sad reflection on the current state of sci-fi cinema.

The film has a lot going for it: Not only are …

Read more

Star Trek—especially in the Next Generation era—was intended as a depiction of a moral ideal. Creator Gene Roddenberry called The Next Generation “an expression of my beliefs,” and he chose to embody those beliefs in the United Federation of Planets, its exploration/defense wing Starfleet, and the characters representing those organizations. Roddenberry…

Read more

Welcome to the Trekker Tom Substack!

Since September 2025, I have been running a growing Instagram account where I talk about science fiction—especially focusing on the ideas it conveys. My goal is to help sci-fi fans think deeply about what really defines great sci-fi: the way it expresses and embodies life-enhancing values such as reason, curiosity, fr…

Read more