Imagine a universe of infinite worlds. Your thoughts might go toward outer space, where other planets orbit other suns, containing a diversity of environments humankind has only begun to discover.
The problem with space is that it’s big.
Complex life forms on other planets in other solar systems in other galaxies almost certainly exist. But if you were to shrink the universe down to the size of, say, a cement truck, finding the worlds with life on them would be like taking a handful of blue sand, mixing it in the cement truck with a full load of white sand and trying to find the blue grains in the resulting pile. Spread that sand out over infinite light-years and you may not find the sand inside a thousand lifetimes, to say nothing of the trouble of traveling those distances in person, especially if the speed of light is in fact a hard limit.
Now as an alternative, consider the many-worlds theory.
In truth, there are at least five different other-universe theories and discussing them properly is the job of a science writer. But take this as a premise: worlds existing in the same space, but separated by some other matter; for the sake of simplicity, we’ll call it hyperspace. In reality as we know it, there is no way to cross that barrier. But lets posit a setting where hyperspace is permeable. Suddenly, not only is it possible to find aliens, but it is frighteningly easy to find yourself on an alien world by accident…
Steernel checked the readouts on his screen again. “Still nothing stirring.”
“Good.” Abergine adjusted her breathing mask, double checked the power cell on her disruptor and looked up the hill. A blocky two-story house with the wood cladding and great picture windows sat atop it. A blanket of new snow covered the old house and its grounds. Halfway down the hill it sat on, the snow ended abruptly. She hadn’t seen a localized weather disturbance so marked before, and the discontinuity was putting her on edge. Local peace officers surrounded the house, shuffling nervously in place and forming a mostly cosmetic barrier. Near the driveway, a van had opened its cargo doors to the house’s occupants who were variously standing or sitting around a portable heater with blankets wrapped over their nightclothes. She turned her attention back to Steernel who was perched on a high seat inside their operations van. “Heavy methane, you said?”
“Yeah. The air-gas mix shouldn’t be a problem but given the enclosed space, play it safe. Careful with anything that might spark, crack some windows for ventilation if you can.”
Abergine nodded and beckoned to her team of Society Enforcers. They were a team of eight, their differences in size, appearance, and number and types of limbs plastered over by cold-weather uniforms. They carried scanners as well as their sidearms and some of them were also-carrying suitcase-sized devices. They began walking toward the house at a measured pace.
“Fan out,” Abergine said, “but stay in visual range of each other. Keep an eye on your scans and keep your distance from the abnormality when you find it.”
The inside of the house could have been any turn-of-last-century house, strewn with the traces of multi-generational family life. Abergine noticed the remains of some rubbery inflatable ball lying by the wall in the entry. The ball had shattered. She prodded one of the fragments with a gloved hand and felt the chill even through the protective layer.
“Hypermantic readings are elevated down toward the basement,” one of the Enforcers reported over the comm.
Abergine closed her eyes. Her own hypermantic senses, though weak on the scale, still had better resolution than the scanners. The hyperspace around them was practically boiling. Trying to concentrate on it made her nauseous, both from the sensory discomfort and the thought of the danger. Rogue portals tearing open in populated areas was bad enough. Rogue portals opening to worlds hostile to people’s safety was worse. But with this much disturbance—
There was a scream and a chorus of accompanying yells from the next room. Abergine ran toward it, trusting her senses would give her forewarning before she ran into anything she’d regret. She came in just in time to see the jagged tear in the air of the living room, the darkness and the swirl of methane snow, ripple and vanish. The Enforcer had fallen back into one of the armchairs, hooked thumbs clawing at the helmet to get it off their now-frostburned face.
She cut in over the ensuing explosion of radio chatter trying not to sound like her heart was pounding. “There’s instability all over here. Get those manipulator beacons up. Walk slowly but do it fast. Don’t fuss with precision. We just need this contained enough to hold until we can work out something better…”
Can you imagine the sorts of worlds you might find on the other side of the portals? You might be familiar with parallel worlds, matching the one we know except for small differences: the same people existing in both worlds but living different lives. Those make for good stories. It’s also a short-sighted conceit to think that those are the most likely option.
You may know this premise: for everything that happens in the world we know, there is another world where something else happened. That’s well enough. But it doesn’t illuminate just how many alternate choices there are, when you consider all the four billion or so years of Earth history.
Think about how our solar system formed. In a chaotic system, the individual movements of one cloud of gas or one fleck of space dust are impossible to track; some chance occurrence arranges them into a system that is like this, not that. Think about biological evolution: genes undergoing random mutations that are passed on to offspring and then survive or not depends on the conditions they find themselves in. Somewhere along the four billion years, some gene, some lifeform, becomes that, not this. Repeat four hundred thousand billion times…
"I still can't believe they sent me here," Drals grumbled. "Seriously. Giant bugs!"
Qhual did his best to keep his face straight. He was asking himself a similar question. The Society of Travelers, with all their meticulous profiling of its personnel, had somehow managed to send an Agent with a bug phobia to cataloged world K4957, local name Gegantu. Wasn't there some other gate tech that could come to this backwater station? Probably not, he thought to himself, trying to resign himself to the fact and meeting resistance. For non-emergency, non critical work? We get the last pick of help I bet.
"Trust me," Qhual said aloud, putting on his best friendly Liason attitude. "The bugs are the last thing you have to worry about. Oh they may hiss and spit at you if threatened and the spit burns your skin a bit, and you regret it for a few days. But that's minor."
"Minor?" Drals exclaimed.
"Yes." Qhual had no desire to belabor the point. He would be failing his current duty as local guide by not mentioning the risks. That didn't mean he had to be overly patient with Drals.
They continued walking down the path to the other end of the gating portal complex. (Drals had arrived via a forced portal some distance away to avoid the malfunctioning main gates.) The path was open to the air, shadowed on one side by a rock wall. Dark, broad-leafed plants grew out of every available crevice, offering a degree of natural shelter from the sun. It did little about the heat which was warm and wet and sat like a blanket around everything, but it could have been worse.
At least, when they got to the transit building, Drals went right into professional mode. Qhual could tell by the seriousness with which he studied instruments and by the muttered incomprehensible jargon. Qhual was here to manage people, and his understanding of multidimensional physics was rudimentary.
Drals looked up from a readout. "Where's your power source for these?"
"The main is underground, as standard," Qhual said, referring to the devices that tapped into the fabric of hyperspace that allowed the gates to function. "But we run solar for the electricity. I can show you."
They climbed stairs up to the roof. "It looks like something is screwing with the consistency of your electric feed. I'll check the likely single failure points first. Transformer, junction box..."
He froze as a hissing sound met their arrival.
The bug (a horribly inexact term, Qhual knew) was about as big as Drals's head. Wings unfurled from under the shell of its compact, round body. Its face that swiveled out from a joint under the shell, complete with pinching mandibles. It reared up on segmented legs to face them.
“Blight!” Drals swore.
“All right, easy…” Qhual said. He glanced around and found the long stick he used to wedge the door open for service access. “Watch your step. It’s already spat at something, see?” He used the stick to point to the discolored spot near a secondary junction box, the door to which was flapping open.
“I’m not moving until that thing’s gone,” Drals protested. His voice had lost volume, but gained pitch.
“You might want to at least duck.” Qhual took a breath to brace himself, lunged at the bug with the stick, then hastily sidestepped. The bug darted into the air, hissing.
A larger shadow passed over them. Something screeched and struck the bug midair, catching it in curved talons the size of large knives. They sank right through the thin carapace with a crunch. The two men on the roof felt the downdraft of the leathery wings as they carried the prey away.
Qhual was the first to break the stunned silence as their heartbeats slowed down. “See, my friend? The bugs are no problem. It’s what eats the bugs that’s scary.”
Drals was not amused.
It won’t be all alien. You’ll find some things the same or similar, if only by complete accident. Classical physics is still in operation. (If there are worlds in which physics as we know it does not function, it is hard to say whether they could coexist at all.) Convergent evolution suggests that different organisims exposed to similar environments, often evolve into similar forms. There tend to be a surprising amount of bipedal sapients wandering around. But the bottom line is that given near-infinite probability space, you are likely to find anything.
Welcome to the multiverse. You’re going to need a guide.