When I was in high school, I really wanted to be a writer. I knew I’d have to write nonstop and suffer for my work if I wanted to be successful at it, which probably explains why I wound up becoming a scientist—it’s like being a writer in the sense that you have to write all the time and that your career prospects are realistically garbage, but different in the sense that you don’t get a cultural pass to wear scarves all the time and smoke cigarettes outside of snowy cafés without getting branded as a massive tool. But even though I’ve read as much Flaubert and Forster on the subway as the next guy (and you better believe I was rocking scarves and a pensive look when I was doing that), I’ll always be a big fat sucker for outlandish sci-fi horror. Whether it be about a group of hyperintelligent seagulls and shark-punching frogmen handling a worldwide birdpocalypse caused by an Egyptian god or a concept-eating basking shark let loose in a hyperdimensional Portland, I always wanted to someday write about an utterly bonkers world-ending scenario or something of that ilk. And in this entry, I’ll try to pitch you my idea for it—the nexocyte.
Cue scary trumpets.
One of the longest-lasting sci-fi horror tropes consists of self-replicating nanobots; nanoscopic little machines that are able to create new copies of themselves without dying in the process. These little nanobots are usually referred to as “grey goo“, and one recent execution of this concept was in the (profoundly mediocre) 2008 remake of The Day The Earth Stood Still. Take a look at the scene involving them below and enjoy one of the few sci-fi action scenes that portrays lab safety protocols semi-accurately:
This flawless self-replicator concept has been around for ages, but for all its countless variants, it’s always stuck to the same simple formula; after they accumulate enough “food”, they’ll generate a copy of themselves while leaving the original “source” individual intact.
Although this seems harmless enough, you’ll find that the number of grey goo nanites in your tacky secret military bunker can get real big real fast. Take it from the guy who invented the concept:
Imagine such a replicator floating in a bottle of chemicals, making copies of itself…the first replicator assembles a copy in one thousand seconds, the two replicators then build two more in the next thousand seconds, the four build another four, and the eight build another eight. At the end of ten hours, there are not thirty-six new replicators, but over 68 billion. In less than a day, they would weigh a ton; in less than two days, they would outweigh the Earth; in another four hours, they would exceed the mass of the Sun and all the planets combined — if the bottle of chemicals hadn’t run dry long before.
But note that these replicators are, in some sense, “dumb”; their reproductive process is entirely independent of the state of the group, which you would expect if each of these little robobugs didn’t know anything about the group/collective/colony it belongs to. But what if it did?
Let’s consider some strange new type of replicator, which I’m going to call a nexocyte, that does know the state of the colony it belongs to thanks to some kind of intra-colony communication network. As a result, its reproductive process can be informed by the state of the colony, and in fact, it may try to clone the colony itself through its (presumably long and arduous) reproduction process.
Although the illustrations don’t make it seem like the nexocytes and the nanites are too different (only a factor of 2 off after the second reproductive cycles), the difference very quickly adds up when you do the math. In fact, I’ll do the math for you:
Look at that—the nexocytes have already hit 65,000 while the nanites haven’t even clocked 50. And, just in case you’re curious, the total number of nexocytes after the sixth reproductive cycle is precisely 18,446,744,073,709,551,616. Let me repeat that; after only six reproduction cycles, the nexocyte colony numbers 18 quintillion, 446 quadrillion, 744 trillion, 73 billion, 709 million, 551 thousand, six hundred and sixteen individuals.
To show precisely how catastrophic the existence of such a replicator would be, let’s envision a scenario like the one quoted above, where each nexocyte has the same mass and volume as an HIV virus, and replicates freely without any concerns for food, chemicals, or the laws of physics. If the timing for the reproductive cycles is the same as above (1000 seconds between each), here’s what the result of each cycle looks like:
Cycles 0-5 (0 seconds to 1 hour and 23 minutes)
Everything here is still well in the microscopic range; even though there are a huge number of nexocytes in our colony by Cycle 5, they’ll collectively be around the size of a dust mite and weigh accordingly too—almost completely imperceptible.
Cycle 6 (1 hour and 40 minutes)
Now we’re getting somewhere. After the sixth reproductive cycle, our little colony is not so little anymore, weighing in at about 40 pounds and measuring up to the size of a decent paint can (4.5 gallons). For some unlucky sci-fi horror protagonist, it will probably be very shocking to see a weird paint can-sized lump of goo pop out of (what appears) to be thin air, but all in all this isn’t so bad! If our protagonist doesn’t get laughed off by emergency services, the authorities might be able to close in on this thing just as it undergoes its next cycle 16 minutes(ish) later. That’s fine, though—I mean, how big could this thing get?
Cycle 7 (1 hour and 57 minutes)
Goodbye protagonist. The nexocyte colony after Cycle 7, if it keeps a nice spherical shape, will be about 840 kilometers wide and weigh in at a whopping 3.4 *10^20 kilograms, which is enough to wipe almost all of the state of New York off the map. Our cute little “nexosphere” is now comparable to the dwarf planet Ceres, and our colony just about makes the cut to be called a dwarf planet (if it was zipping around in orbit instead of crushing our protagonist’s internal organs). This will definitely grab your omniscient secret government of choice’s attention, and if we’re very lucky, they’ll get their ducks in a row and let more than a couple of ballistic nukes rip on this thing by the sixteen minute mark. Because if not…
Cycle 8 (2 hours and 13 minutes)
…goodbye solar system. Our former little dwarf planet is now a sphere bigger than most small galaxies and about a hundredth the width of the Milky Way, with a radius of 309.1 light-years. That’s right: it would take light 309.1 years to travel from one end of our nexocyte colony to the other. Luckily, it won’t splat over the entirety of the Milky Way, and will definitely (and finally!) grab the attention of the advanced alien civilization of your choice. And luckily, they won’t even have to do that much to get rid of the nexocytes either!
Because they’ll become a black hole.
See, it turns out that our galactic-sized ball of nexocyte is sufficiently massive (35,000 times the weight of the entire observable universe) to cause it to become a black hole orders of magnitude bigger than any black hole that could ever plausibly exist. Our alien friends will simply have to enjoy whatever of life’s simple pleasures they can get before they’re sucked into the black hole/thrown off their orbit/fried with ionizing radiation/etcetra as the Milky Way slowly but surely collapses from the sudden disruptive presence of the nexocyte singularity.
So there you go; our colony of nexocytes may not be as long-lived as the nanites’, but we did get to destroy the Solar System in 2 hours, 13 minutes and 20 seconds (with the Milky Way getting sucked in soon after). Luckily for us, this kind of replicator is completely implausible, because it would take too much time and resources for it to replicate its colony! The only way this replicator concept would ever even potentially get off the ground is if it existed inside of a medium with nearly unlimited amounts of energy compared to each nexocyte’s energy consumption, and where information exchange between nexocytes could be extremely fast and efficient—and even then it would just wind up wrecking the place at breakneck speed. Good thing a place like that doesn’t exist, huh?