Cat Flap

There are incredibly complex beings that exist in thirteen dimensions. Humans can only perceive these beings as the shadows they cast onto our paltry four dimensions. We call these shadows “cats”.

It’s no coincidence that Schrödinger chose a cat for his thought experiment. He knew something was up with them. Cats ignore the laws of physics. To be fair, cats ignore a lot of things: their human companions, generally-accepted sleep schedule guidelines, geopolitics, etc. But they particularly ignore the laws of physics.

Physics says, “Cat, you can’t land upright just by wriggling about a bit in free-fall.” The cat performs a perfect four-point landing, then wanders off to find a convenient sun ray. Physics says, “Cat, you can’t fold yourself up to fit into a box half your own volume.” The cat climbs in, yawns, and dozes off. Thirteen-dimensional beings can be like that.

There are things that cats decidedly do not ignore: birds, can openers, random dust motes, blank spots on the wall. It’s these last two in particular that often puzzle the casual observer, and that’s mostly due to the fact that, unsurprisingly, things are not always what they seem.

Melissa Yuen’s cat – note that this is an extreme rhetorical shortcut for “the four-dimensional shadow of a thirteen-dimensional being which was definitely not owned by, but happened to choose to exist in the general proximity of, Melissa Yuen” which, let’s face it, is a bit wordy – was named Pickles. Pickles was, by most measures, a typical cat. He ate, slept, shredded and/or desecrated Melissa’s most valuable possessions, and stared at dust motes, blank spots on walls and/or birds.

Melissa, for her part, was a typical human. She ate, slept, worked, bought valuable possessions for Pickles to destroy, and occasionally wondered what the hell her cat was staring at.

“What the hell are you staring at?” she asked, looking up from her book. The cat was alternating his attention between a dust mote and a blank spot on the wall.

Pickles completely ignored her – not that this was in any way atypical. He shifted uncomfortably as the mote drifted toward the wall. It grazed the wall, causing it to ripple slightly, and prompting a low mrrr from Pickles. The mote then looped back around and slid silently into the wall. Pickles hissed menacingly at the impact point.

Nothing happened. Pickles continued to hiss and mrrr at the nothing. It should be noted that, while Pickles was extremely agitated, the thirteen-dimensional being barely noticed. It’s a bit like if you had a minor scratch. Not a big deal for you but, for the leukocytes in your bloodstream, it’s a call to arms.

“Stupid cat.” Melissa put down her book and went over to see what all the fuss was about. “There’s nothing there! Look,” she said, looking down at the cat and patting the wall, “it’s just a wall.”

Her hand came into contact with something decidedly un-wall-like. She looked up to find an irregularly shaped hole in the wall, through which, she could see... well... herself.

It was like looking in a mirror but not. What you see in a mirror is a backwards image of yourself. This was more like looking at a webcam image of yourself, where the image hasn’t been reversed. It was the right way around, but looked wrong. Also, it wasn’t an image. It was another person. Another her. The two Melissas stood there for some time, frozen in an awkward high-five.

“Um,” they both said, lowering their hands.

Pickles had stopped hissing and was now attempting to reach the hole by alternately leaping and clawing at the wall.

“How the hell...” they both continued.

“This is really weird,” they said, reaching through the hole into each other’s identical living room. They shook their heads.

“Any idea how...” they both began.

“OK, you go first,” they said. “No, you. No... Dammit. Um...”

“Hold on,” they said, and each went to find a quarter.

They returned simultaneously, and said in unison, “I’m going to flip a coin. Heads, I talk first. Tails, you talk first. Chances are we won’t both get the same results.”

They flipped their respective coins. “Heads” they said. “Tails. Tails. Heads.”

After twenty consecutive coin flips, they gave up. “I’m going need some help with this,” they said.

Melissa walked away from the hole to make a phone call in private, away from her other self, who presumably was doing the same thing. She got Lisa’s voicemail. “Hi, it’s Melissa. There appears to be a window into another universe in my living room. As far as I can tell, it’s identical to this one. Like, spookily identical. Thought you might want to have a look at it.”

With that, she sat back down and started reading her book again, pointedly ignoring both the hole in the wall and Pickles, who was completely failing to gain access to the hole, but was succeeding in ruining the drywall immediately below it.

The phone buzzed. A text from Lisa: “BRT”.

And she was. Lisa showed up at her door, breathing heavily. She’d probably run all the way from her car. She looked like she’d just woke up, showered, thrown on whatever was lying on the floor, and rushed over. She did, however, have a large duffel bag slung over her shoulder.

Melissa did a quick mental calculation. “You either ran every light, or were seriously hoofing it.”

Lisa dumped the duffel bag on the floor and grinned. “A little from column A, a little from column B. Now, let’s see this...”

She stopped, open-mouthed, and stared at it. “You weren’t fucking kidding,” she breathed. “How come you always have all the fun?”

“There’s a great big damn hole in my wall,” Melissa pointed out. “I wouldn’t exactly file that under the heading ‘fun’. Also, walk up to the hole and have a look at who’s on the other side.”

Lisa approached the hole. As she did, another Lisa approached from the other side. “Holy shit, it’s me,” the Lisas said.

“Oh, good, I thought it was me,” Melissa quipped.

Lisa spun around. “You’ve got a wormhole to another universe in your living room, and you’re telling bad jokes?”

Melissa shrugged. “You get used to it. I figure, if she does everything I do, I’m pretty safe. I mean, it’s not some sort of evil parallel universe where everyone has a goatee or something. As long as I don’t try to stab her, I’m pretty sure she won’t stab me.”

“OK, fine, sure. But the wormhole itself might not be safe,” Lisa replied. “Mind if I bring in a few people to have a look at this thing?”

“Hey, you’re the expert,” Melissa said.

“Not on this sort of thing I’m not,” Lisa replied. “But I do know someone who is.”

Melissa nodded. “Go for it.”

Lisa was one of Melissa’s more interesting friends, and that was saying something. Her circle of friends included artists, astronomers, forensic anthropologists, nuclear physicists, toxicologists... and that was just in her contact list. A couple more degrees of separation, and you got into some really wild stuff. Lisa was a theoretical physicist, the closest Melissa could think of to an expert on this thing, whatever it was. Naturally, her network would include people even more qualified to handle this. And that was pretty much what Melissa was counting on.

Lisa took a few pictures and sent some texts. “Somebody will be here soon.” She looked down at the cat, who was still attempting to scale the wall. “What’s with Pickles?”

Melissa shrugged. “He’s been doing that ever since it opened up. A little before that, actually. So, what do we do while we’re waiting?”

“You said it’s identical on the other side. You’ve tried coin flips?” Lisa asked. She had her back to the hole. Melissa could see the other Lisa and Melissa having the same conversation behind her.

She nodded, handing Lisa the quarter. “Twenty tries, all the same.”

Lisa took the coin, tossed it in the air a few times, then suddenly spun around and threw the coin through the hole. An identical one, thrown by the other Lisa, came through from the other side, bouncing off Lisa’s left shoulder. “Sorry,” they both said. “No problem,” they both replied.

She took Melissa’s arm and led her away from the hole. “OK, that’s kinda freaking me out,” she muttered. They headed into the kitchen, leaving Pickles to stand guard.

“Yeah,” agreed Melissa. “It’s hard to have a conversation with yourself when you keep saying the same thing at the same time. I tried to use the coin flips to break the tie so that we could take turns talking. You can see how well that went.”

Lisa glanced in the general direction of the living room. “Maybe we need something a bit more random.”

More random?” Melissa chided. “Something’s either random or it isn’t.”

Fine,” Lisa conceded. “You know what I mean, though. Coin flips are one thing, but radioactive decay... that should actually be random.”

“And how exactly are we supposed to...” Melissa began, but Lisa was already headed to the front door.

“I brought a few things with me,” Lisa explained, rooting through her duffel bag. “Here we go,” she said, pulling out a Geiger counter and a small plastic container. She headed back toward the hole.

“You brought a Geiger counter with you?” Melissa asked, trailing behind her.

“And a cesium 137 check source,” Lisa replied, proffering the plastic box. “Thought it might come in handy.”

Melissa glanced back at bag. “I’m hesitant to ask what else you thought might come in handy.” She nodded at the cesium. “Is it safe?”

“You’ve got a great big wormhole thingy in your living room,” Lisa pointed out. “I think we’re way beyond worrying about ‘safe’ at this point.”

“That really doesn’t answer my question,” Melissa countered.

Lisa ignored her, addressing the other Lisa instead. “OK, whoever gets the higher total count,” they both said, “gets to speak first. Ready... Go!”

Each Lisa turned on her respective Geiger counter and held it up to the check source. The counters ticked rapidly, and the “total count” display blurred as the numbers rolled up.

“Stop!” the Lisas said, pulling the cesium away. They held up the Geiger counters and compared results. “Dammit!” they said in unison.

“Best two out of three?” Melissa suggested. She tried to ignore her counterpart making the same suggestion.

“No point,” Lisa said, taking the Geiger counter and cesium sample back to the foyer, and putting them back in the duffel bag. “There’s no way those two numbers could’ve been the same. I don’t get it.”

“And as for what else I have in here,” Lisa continued, “most of it depended on being able to interact in any meaningful way with our counterparts.” She nodded towards the hole.

“For example?” Melissa prompted.

“EM meter, recording device, history books, weapons... the usual,” Lisa replied.

Melissa gave her friend a dubious look. “Weapons?”

Lisa shrugged. “No guarantee they’d be friendly. Moot point now, though. They seem to be identical to us, so all that other stuff is useless.”

The door bell rang. Melissa checked the peep hole. Three people stood outside, each wearing a crisp, gray jumpsuit with “AAA+++ Plumbing” emblazoned across the chest. Each carried a toolbox with the same name stenciled on the side. “Did you by any chance call a team of plumbers?”

“That’ll be my friends,” Lisa said. “They’re not really plumbers,” she added, in case it wasn’t obvious.

Melissa let them in. “Hi, I’m Melissa.” The trio stood just inside the doorway, managing to look both official and awkward, and not at all like plumbers. “And you are...” Melissa prompted.

“You can call me Alpha,” said a woman whose demeanor seemed to be as neatly-pressed as the creases on her jumpsuit. She appeared to be in charge.

“Is that your first or last name?” Melissa asked.

“It’s what you can call me,” Alpha said curtly. “And this is Bravo and Charlie.” A chubby young man with chaotic hair and an even younger woman with polka-dot rimmed glasses and multi-colored hair nodded in turn. Charlie waved and said “Hi”, prompting a stern look from Alpha.

“Now then, where’s this purported anomaly?” Alpha continued.

“Right through here,” Lisa replied, gesturing toward the living room. “It’s on the wall, just above the cat.”

As the trio passed, Melissa turned to Lisa and mouthed, “Purported?”

Lisa rolled her eyes and muttered, “Just go with it. They know what they’re doing. They’re just a bit eccentric.”

The three clearly-not-plumbers opened their toolkits and began assembling a collection of bizarre-looking, haphazardly-built instruments. These were then mounted on tripods and adjusted to roughly the height of the hole in the wall. Each one clicked, buzzed and beeped to announce that it was doing some very, very serious measurements, and was totally not just a bunch of spare parts someone had welded together because it looked cool. An identical set of instruments was being assembled on the opposite side of the wall.

Pickles had given up trying to scale the wall, and was now getting underfoot, yowling for attention. Charlie reached down once or twice to scratch his head and make soothing noises.

While they set up, Melissa pulled Lisa aside. “What’s the deal with these guys? I mean ‘Alpha Bravo and Charlie’? Seriously? And what about those plumber getups?”

“Yeah, well, they’re a bit eccentric,” said Lisa. “Charlie’s the one I contacted. Not her real name but, if that’s what she’s going by today, it’s best to play along. I don’t want to piss anyone off. Bravo and Alpha are really good at what they do, but Charlie’s amazing. If anyone can figure this out, it’s her.”

“Charlie?” Melissa said. “But she’s just a kid.”

“That kid already has one PhD and she’s working on another,” Lisa replied. “A real wunderkind. When it comes to theoretical physics, she can run circles around most of us.”

“Huh,” said Melissa. “And the plumber outfits?”

“Alpha is a bit paranoid,” Lisa explained. “Thinks they’re being watched all the time. Black helicopters, Illuminati, tinfoil hats, that sort of thing.”

“Jeez, really?” Melissa rolled her eyes.

“Hey, I told you they were eccentric,” Lisa replied. “And they pretty much come as a package deal. You call one of them, all three show up. Don’t worry, they’re really good at this sort of stuff.”

Melissa raised an eyebrow. “Does this sort of thing happen a lot?”

“More often than you’d think.” Lisa shrugged. “Well, not this but, yeah, I get calls about weird shit all the time. If it’s interesting enough, I call these guys.”

While Alpha examined the readouts on the various instruments, Bravo took precise measurements of the hole’s shape, and Charlie documented everything with a notebook and camera.

“The opening is laterally symmetrical,” Bravo observed, “indicating a strong correlation between the two universes.”

“Yeah,” agreed Lisa. “We tried coin flips and a Geiger counter, and couldn’t find any differences.”

Alpha huffed. “Yes, well, our much more thorough examination,” she said, patting one of the instruments, “confirms that there is, indeed, no measurable difference between the two universes.”

“It could be another universe, identical to this one,” Bravo added, “Or it’s possible it’s actually our universe, and the wormhole just loops back on itself.”

“What’s the difference?” asked Charlie, looking up from her camera.

Bravo snorted. “Well, one’s one universe, and the other’s two universes,” he explained in a condescending tone.

“Sure, but, if you can’t tell the difference, is there a difference?” Charlie countered.

“OK, look...” Bravo began huffily.

Charlie continued her thought, ignoring him. “What I mean is, if two universes are exactly the same – every single particle is exactly the same – then the two universes occupy the same quantum state. Therefore, they are the same universe, not just practically, but actually the same. Right?”

Bravo opened his mouth to speak, shut it again, then gave Alpha a quizzical look.

“It’s a distinct possibility,” Alpha agreed, nodding sagely, either in understanding or in an effort to pretend she understood.

“Also, it’s not a wormhole,” Charlie pointed out. This prompted a huff from Bravo which, in turn, prompted a glare from Alpha.

“Then what is it?” asked Lisa.

Charlie shrugged. “Not sure, but it’s definitely not a wormhole. The endpoint of a wormhole would be spherical. Looking into one this size would give you a distorted view of the other end. Sort of like looking through a fish-eye lens.”

“This thing,” she continued, nodding at the hole, “is flat and irregularly shaped, but symmetrical along one axis. I don’t think there’s a name for that, but ‘portal’ will do for now, I guess.”

Melissa began to see what Lisa meant about Charlie. She turned to address her. “So, if that’s our universe, that person over there really is me, and this portal thing is just some sort of multidimensional fun-house mirror?”

Charlie nodded. “That’d be my guess, yeah,” she agreed, putting down the notebook and camera, and picking up the cat, who’d been wandering around yowling the entire time. “Poor thing. What’s his name?”

“Pickles,” Melissa replied. “He’s been fussing all morning. Don’t know what’s got into him.”

“Not surprised,” said Charlie, cradling the cat. “Cats hate spacetime anomalies. Isn’t that right, Pickles?”

They all stared at her.

“Cats... hate spacetime anomalies?” Alpha repeated. “Where on Earth did you get that from?”

Charlie seemed genuinely surprised. “Oh! I thought that was common knowledge. Chasing dust motes, staring at walls... what did you think they were doing?”

“Chasing dust motes and staring at walls.” Melissa ventured. “Come to think of it, Pickles was doing both of those things, right before this thing appeared.” She gestured at the portal.

“Well, that explains everything!” Charlie exclaimed.

Everyone else stared at her in a way that conveyed, very clearly, that it did not, in fact, explain anything at all.

Charlie stared back for a few seconds, then apparently realized her error. “Oh, um... See, about one in a million dust motes are actually coronas generated by the endpoints of microscopic wormholes. Perfectly harmless... most of the time... I think. And the wall thing has something to do with weak spots between parallel universes... or something. I’m still trying to work out the math on that one. And, if one collided with the other... wow, I’m not sure what’d happen. Probably something like that.” She nodded at the hole.

“And cats?” Lisa prodded.

“Oh, right,” Charlie continued. “Cats are weird. They can detect these phenomena... somehow, and... well... they don’t like them. They get really edgy.”

Charlie walked over to the portal and turned to face it. “See, the closer I get, the more agitated he becomes. Oops!”

Pickles leapt out of Charlie’s arms and dove toward the center of the portal, running face-first into the other Pickles, who was in the process of leaping from the opposite direction. The two cats collided, bounced off each other, and drifted backwards, coming to a rest about a meter from the portal. Pickles seemed to be unharmed by the impact, except for the fact that he had completely failed to fall to the floor.

“Um, why is my cat hovering?” Melissa asked in what she hoped was a casual voice. She looked around. “Anyone?”

Lisa shrugged helplessly. Alpha fiddled with her instruments. Bravo took careful measurements of Pickles’ current position. Charlie stared at the cat, brow furrowed, lips moving silently.

“Fine,” Melissa said, and moved to retrieve her cat from mid-air.

“No! Wait!” Charlie exclaimed, reaching out to pull Melissa back. “Don’t touch him. Look.”

Pickles began to transform. He cycled though various shapes: a cat, an oblate spheroid, a set of five rippling columns, a lumpy dodecahedron, something that looked a bit like a pretzel – if pretzels were covered in gray-striped fur – and so on. Stripey, gray, fur-covered blobs separated and merged, flipped and folded, stretched and compressed.

Melissa stared at the gyrating blobs that used to be her cat and, trying to keep her voice as steady as possible, asked, “Charlie, what’s happening to my cat?”

“I think... I think he’s turning around,” she replied.

“I’ve seen Pickles turn around before,” Melissa pointed out. “This is definitely not how he does it.”

“I think... yes... I’m pretty sure he’s rotating around a hyperdimensional axis,” Charlie explained. “Um, several different axes, actually. That last transformation was pretty complex. You’d need at least... seven dimensions to pull that off without turning inside out or ripping yourself to pieces... Sorry. Um, I’m sure Pickles is fine. He’s just... a bit too complex to be described using four-dimensional geometry.”

“He’s a cat,” Melissa pointed out.

“Yeah,” Charlie agreed absently, watching Pickles’ gyrations. “Cats are weird.”

Pickles finally settled into an irregularly-shaped blob that then hurled itself at the wall, covering the portal. The blob flattened into a paper-thin film, then began to contract, dragging the edges of the hole with it, shrinking to a single point, which then vanished altogether.

“Yeah,” said Charlie matter-of-factly, “And they really don’t like spacetime anomalies.”

“Well then,” announced Alpha. “That seems to have resolved itself rather neatly. Alright team, let’s pack up and head out. We’ve got a lot of data analysis to churn through with this one.”

“Excuse me!” Melissa protested, barely containing her frustration. “My cat just disappeared!”

Charlie smiled sympathetically. “Don’t worry. He’s still nearby... somewhere... probably. Just, y’know, not in any of the directions we can see. I’m sure he’ll turn up eventually. Cats have a knack for finding their way back home.”

“Maybe you could run the can opener,” Bravo suggested, looking up from his toolbox.

“Yeah, thanks,” Melissa replied rolling her eyes.

She turned to Lisa. “You say this sort of thing happens all the time?”

“Well, weird stuff, yeah,” Lisa replied. “But, no, reflexive spacetime portals and disappearing hyper-dimensional pets are a bit over the top, even for this crew.”

“You think Charlie’s right?” Melissa asked hopefully. “You think Pickles will turn up again?”

“Hope so,” Lisa replied sympathetically.

Melissa stared at the spot on the wall where her cat had disappeared. “I know he can be a pain in the ass but, well, you know...”

“Yeah,” Lisa said. “I like him too.”


Melissa waited all Sunday afternoon for Pickles to return. She called for him. She searched the apartment. She even ran the can opener a few times.

The next day, she printed a few “lost cat” posters and taped them up around the neighborhood before heading to work. She didn’t really think anyone would find him. It wasn’t like he’d slipped out the front door or anything.

That evening, she did a quick search of the apartment again, made herself some dinner, and sat down to read. She heard the hinges on the bedroom door creak, and looked up to see Pickles squeezing through a gap in the doorway less than half his width, the way cats do.

“And just where the hell have you been?” she asked.

He ignored her and strolled past, into the kitchen, where he quickly emptied his food dish.

“Oh, don’t give me that ‘I’m just a cat’ bullshit,” she said. “I saw what you did. I don’t know what you are, but you’re definitely not just a cat.”

Pickles sat on the floor in front of her, back turned, and began cleaning himself.

“You hovered in the air,” Melissa pointed out. “You turned into all sorts of weird shapes. And you erased that... portal thing. That’s not typical cat behavior.”

Pickles climbed up on Melissa’s lap, closed his eyes and started to purr.

Melissa sighed. “Fine,” she said, stroking the cat’s fur. “You win. Just, y’know, promise not to let any of that stuff happen again, OK?”

The purring stopped. Pickles lifted his head, opened his eyes, and stared at her. For a fleeting moment, Melissa saw beyond the cat, beyond this four-dimensional shadow curled up on her lap, into the eyes of the being who cast the shadow.

She didn’t so much hear it as feel it. The reply came from a point deep within the cat’s eyes, but it also came from all directions at once, including those directions Melissa couldn’t see or even imagine. “I make no promises,” it said.

Melissa stared wide-eyed at the cat. Had that just happened? If it had, what exactly had happened?

Pickles lay his head back down and resumed purring, like a perfectly ordinary cat. He very pointedly gave no indication that anything at all had occurred. He was obviously just a cat. Nothing to see here, folks. Move along.

Melissa sighed again. “I really should’ve gotten a dog.”