They stood, the human and the Tensor, at an Accelerator station occupying the same geography as a former nickle mine in the Tienshan Mountains. Above ground, the land was dry and severe, but down here the Quotidians had done their best to make the place feel like a tropical lagoon. The jungle-gym walls curved down to cup a slightly spongy floor, which in turn sloped down to the centimeter-high wall of the Accelerator ring itself. It currently held outbound cargo, upon which crouched a handful of Quotidians – tourists, politicians, or stevedores. The wall on the opposite side of the room glowed with rippling silver light, suggesting great distances and depths.

Laura looked down, trying to stop thinking of a disk-shaped god the width of the universe. Her eyes rested on the Tensor's luggage, which chittered.

"Ah," said the Tensor, as Laura noticed the luggage's suspicious air holes, "you want to see my little Scuttly? I will make her container transparent."

He did so.

"Eugh!" said Laura.

"Translation error?"

"Oh!" her voice had gone shrill. "It's a giant spider."

"Translation error or mistake. It's not an arachnid. The arachnids went extinct on the earth of my home timeline and vipers evolved to fill the space left empty. Do you see how the legs are actually highly modified jaw bones? And they still deliver poison!"

"Heeeeeee!" squealed the enraged spider-snake.

Laura made the same sound, but quieter, in the back of her throat. She was abruptly conscious of the smell of this place. Sweat, artificial mucus, civilized urine, and the pheromones of a dozen major clades. It smelled like a zoo, like a jungle, like a den of monsters.

Waves of horripilation swept across her forearms and neck, tiny hairs trying to stand up and make her look more intimidating. Overcome by xenophobia, Laura bared her teeth at the nonhumans surrounding her.

"Oh, what an interesting mouth you have," said the Tensor. "You know I am a testal hygienist by profession. I examine and clean a person's protruding hard parts."

Laura shivered with the force necessary to stop herself from running away.

"Although it's odd." The Tensor played lasers across her still-clenched jaw. "I thought Adventurians had fewer teeth."

Laura looked at him.

"What?" she eventually said.

"Yes, I distinctly remember reading that Adventurians have only six teeth, which meet to – "

"I'm not an Adventurian," said Laura. "I'm a human."

"A what?"

"A human. I'm represented by the United Nations."

"No, no, you're an upright biped, of that I am quite sure. It's a very rare body-type, known only in Adventurians."

A brief aside, because the Adventurians were somewhat famous at that time.

The crew of the star ship Adventure departed from its earth 200 million years ago, bearing a crew descended from Suminia.1 They spent several subjective years traveling to the other side of the Virgo Cluster and back at relativistic speed.

Because the speed of light must be the same for all observers, as an object approaches the speed of a photon, it must experience time more slowly. Otherwise, it would catch up to the photon, right? If you accelerate without stop at 1 gravity, you (or, in fact, if the Adventurians) will arrive and be able to return in less than a lifetime. But for the rest of the universe, much more time has passed.

The Adventurians knew that. They expected to return to a home world changed by a hundred million years of un-dilated time. However, they also expected to find some sign of life elsewhere in the universe. They expected their sacrifice to mean something.

Having returned to an abandoned and unrecognizable earth, with nothing to show for their efforts but discoveries in astrophysics, the Adventurians were understandably depressed. Then, their ship's chief engineer noticed an anomaly in the antimatter generator. The anomaly seemed to be a sequence of prime numbers. After exploring the galaxy and losing their home, the Adventurians had stumbled upon the Convention of Sophonts.

It was a stirring story, which explains why the Tensor so wanted to meet an Adventurian. Laura knew that, but now the question was what to do about it.

Koen would have said, "Adventurians are anomodont therapsids. They lay eggs and have bony ossicles. I have hair." Mark would have pretended to know a member of the celebrity-species. Laura, who was in charge of both of them, closed her eyes and took a firmer grip on herself.

"I am here to meet someone who will be able to explain the situation," she told the Tensor. "While we wait for him, may I have your contact information? Perhaps you and we, and the Adventurians, will find we can work profitably with each other."

Did you know this story is from Royal Road? Read the official version for free and support the author.

"Of course," said the Tensor, emitting radio waves in the frequencies of disappointment and shame. It is considered rude to mistake one species for another. "I will fire my business card at you as soon as it has gestated."

"Clarify?" said Laura, faint with exhaustion.

And Koen arrived.

***

On one earth, a timer in a computer reached 0. On another Earth, the same happened. On both, in the same place under the Tienshan mountains, electric charge began to build up. Electrons flowed through superconducting spirals, generating powerful magnetic fields. These formed a pair of rings, around which protons were tugged at increasingly ludicrous speed.

Imagine two circular saws stacked one on top the other. They are almost, but not quite parallel to each other. At one blazing point on their circumference, they meet.

If the magnets failed, a pair of proton beams would scissor out of the side and obliterate quite alot of western Chinese mountainside. But the magnets did not fail. They ground the rings of protons against each other, and at a two-femtometer-wide region of space a possibility opened up. On the other earth, the same thing happened, just a skosh to the right.

Quantum states decohered for half a billion years found themselves once again sharing a state. Causes that should have had no effects grabbed onto the tiny hole in reality and yanked. Like two buzz saws kissing, the proton beams wobbled, their blazing point of intersection sweeping out a circle as wide and deep as a swimming pool.

For a moment too brief to be observed, space-time unzipped.

Of course quantum laws couldn't be having with that, not with so many people watching. The wave function immediately collapsed, and Koen was still where he'd always been. But the accelerators were still working on both earths, and in another infinitesimally small slice of time, space unzipped again. Again, Koen was both on his Earth and on Quoditia (with a cargo container full of garbage overlapping with his left arm). Again they collapsed, again they superimposed.

Imagine flipping a coin so fast that you can fit a million heads-in-a-row into the time it takes to walk across a room. Imagine doing that, and waiting for the coin to land on its edge.

To Laura, watching the accelerator while she pretended to listen to the Tensor, the air seemed to flicker. The stacked boxes stuttered in and out of reality. There, a cargo container was briefly replaced by a tall figure in a white biohazard suit. He vanished, reappeared, looked around, made to step out of the accelerator, and vanished again. When he reappeared, he was standing stock still.

Koen felt like an idiot. He had been told repeatedly not to move about until his wave function had come to a complete collapse.

He stayed where he was, therefore, until stevedores stepped into the ring and started unloading the crates of lumber, hard drives, lithium borohydride, and complex little pyramids. These stevedores were Quotidian, and flickered their eyeballs at Koen. He had studied up on Quotidian body language, and tentatively identified mild amused contempt.

He didn't care.

Koen staggered, exhausted, weighed down with luggage, thoroughly sous vide inside his bio-containment suit. His journey was only halfway through.

But nonhumans were all around him.

There were Quotidians here, and arch-shaped Catenaries, marionette-limbed Neurospastics, and dozens of other species Koen couldn't recognize. Some his paleontolgist's training could at least general identify outlines. Cephalopod, sea-cucumber, eurypterid. With others, he couldn't even pin down the phylum. Could that amorphous clutch of slowly-growing lavender and crimson tentacles be a sapient sponge? A slime-mold? A fungus? A dozen species at least, each evolved from something other than fish. Not "creatures," not "beasts." Not "animals," except in the sense that all people were animals.

And there, standing next to a giant sparkling cylinder, was Laura.

Koen's feet moved faster. So did his heart, in response to the hormone adrenaline, produced by the adrenal glands above his kidneys, which in turn had just been triggered by Koen's amygdala and hypothalamus, reacting to signals filtered through his visual and cerebral cortices, ultimately triggered by the play of light and shadow across the retinas in the back of his eyes, and across Laura's face.2

It had been a year since they'd last seen each other in the flesh. Their communications since then had been mostly text-based, and entirely professional.

Laura, whose amygdala was already active in response to her conversation with the Tensor, increased its signal output. Her own adrenal glands produced cortisol, which constricted her blood vessels, and epinephrine, which bound to her liver to release glucose into her increasingly pressurized blood.

"Why is your skin becoming warmer?" asked the Tensor. "I hope you're not ill."

More or less the same processes were working in Koen's abdomen as Laura's. Only, some of his adrenal secretions were processed by his testes into testosterone.

He surged forward with new strength in his limbs, telling himself he wanted nothing more than to collapse into Laura's arms and sleep.

Laura brought up her hands to shield her throat. She told herself that she was still scarred by the memory of people in biohazard suits. She also told herself that she didn't like this feeling, which was almost, but not entirely unlike fear.

Koen recognized her expression and stopped, breathing more heavily than was comfortable in his suit. I missed you, he wanted to say, but he could see that he'd scared her. That shamed him and, although he refused to recognize it, gave him pride as well.

These emotions, and his reactions to and suppression of them, consumed all of Koen's cognitive resources. He might have said, "hello," or "thank you for coming to pick me up" or even "it's good to see you, Laura," but didn't. He just stood there, trying to get oxygen into his brain.

Laura told herself that she was waiting for him to speak, while she got on with the business of dealing with her own emotions. What she wanted to say was, and now here's another problem I have to deal with!

The light from the spinning Tensor lit them, refracting in rainbow spangles off the curve of Koen's visor. The two humans looked silently into each-other's eyes, poised upon the silent peak of social awkwardness.

1 Imagine an iguana with bigger teeth, although Sumnia was actually more closely related to you.

2 Calabrò RS et al. "Neuroanatomy and function of human sexual behavior: A neglected or unknown issue?" Brain Behav. 2019 Dec;9(12):e01389. doi: 10.1002/brb3.1389. Epub 2019 Sep 30. PMID: 31568703; PMCID: PMC6908863.