Ah, fun times. Fun times.
Anyway, what I thought would be
Writing science fiction of course means that I don't need a science background, even though I have one: I have an actual science degree (well, political science, but as Albert Einstein said: "Stop quoting me.") The whole point of fiction is to make stuff up, so I try to do as little research (or thinking) as possible whenever I'm writing. And in general.
So as I wrote the book, I'd just throw in whatever ideas I thought might work in the setting of the novel. Codes takes place in the near future, an era invented by Phillip K. Dick. It's a world that's mostly recognizable: there are colleges and strip malls and cars, and the cars do not fly, but there are little touches here and there that demonstrate things are more advanced then our everyday lives. Those are the things that say this is the future: things like the Gravity Sling store where Robbie, the main character, works. The Sling is a service that will fling your package into low-Earth orbit for a reasonable price.
(To be fair, that's not something I invented entirely; scientists already envision that being possible at this point -- Arthur C. Clarke dreamed it up in 1950, calling it a "mass gun." So while I didn't make it up, I did have the creativity to locate it in a strip mall next to a defunct retro-sandwich shop.)
But the Gravity Sling franchise doesn't really factor into the story. So let's talk about something that does: the deadly weapon I invented for the bad guys to use. I call it the ping.
What, you say that doesn't sound frightening or deadly? Shows how much you don't know. The ping!, is a projectile shooter. It shoots something like a BB, only obviously a lot faster, and it gets its slang-name from the sound the projectiles make (ping!, in case hadn't made the connection yet.)
What makes the ping! so deadly is that the projectiles are made of a special -- and undescribed, in the book-- kind of material that allows them to ricochet, with almost perfect conservation of energy, off anything more dense than, say, an eyeball. When the projectile is first fired, it can pass through the first layer of skin, or the aforementioned eyeball, or eardrum, to get into the human body.
The pings don't pass through anything that's not organic, so if you just shoot wildly into a room, they'll keep rebounding and rebounding until they hit something organic.
And then once it does hit you, the ping can really tear you up: most of the time it's going to enter the skin and then rebound off the other side of you -- the inside -- and back around and around without ever breaking out, shredding whatever part of you they happen to have gotten into. Only rarely will a shot pass right through you and do little damage. The rest of the time, you're turned into a bag of skin holding an organ puree. The security guards who actually serve as the police force, at least in this part of the city, use them because they're quiet, don't have to be too accurate, and almost always kill the target.
So ping guns combine a bit of shotgun with a bit of what killed Snowden in Catch-22 (that's a literary reference! I read a book once! And remembered it!) with some maybe-almost-accurate science.
Now, the question I was thinking about as the book becomes a reality is: could the ping! actually exist in real life?
Having not researched it at all before I wrote the book, I didn't know -- but I looked it up now, and it turns out it could, actually, possibly, be a real thing someday.
What follows is based on roughly 22 minutes of skimming around Wikipedia and googling things like "what is the tensile strength of the human liver," which is the kind of search history I like to think keeps the NSA working overtime when they see it. MY TAX DOLLARS AT WORK. Here's what I figured out about how these deadly future guns would be possible.
First up is conservation of momentum. If a ping! is going to keep going and going and going, it's going to have to keep its momentum in a collision with a wall or your skull or the lamp.
Science says this: whenever two objects collide (assuming all the perfect-experimental-conditions etc) the momentum of the two objects is perfectly preserved, so that the momentum before the collision is the same after. That's because object A imparts momentum to object B, and vice versa. Think of a bat hitting a ball, or an skateboarder hitting the ground:
The momentum lost by object 1 (the bat, or the skateboarder) is gained by object 2 (the ball, or the Earth.) Here's a video that helps actually demonstrate what's going on. (PS I didn't watch the video, I just copied it from a site that said it explained things, so if it doesn't explain things or its porn or something don't get mad at me.)
Ping projectiles couldn't go on forever, both because they're losing momentum when they collide with something that doesn't impart momentum back to them -- a wall, or your dead body -- and because this isn't an experimental system and so there are things like friction and gravity working on them, too.
But they could go on a long time, especially if fired with sufficient velocity (necessary, given the tiny mass of the projectile itself.) So that part is true enough: a projectile, if made of the right things, and fired with enough power, could theoretically keep rebounding long enough.
Then there's the bit where the projectile passes through organic material but not inorganic material, o at least not strong inorganic material, because the pings have to go though clothes.
That seems more possible even without research: bullets, after all, ricochet off things but pass through skin. But the pings don't just rip through your skin and keep going: they rebound back off the inside of your body, so they have to be able to pass through human skin only once.
To do that, first, Ping projectiles would have to pass through almost anything that's equal to or less than the strength of human skin, but bounce off of anything stronger. So that means we're talking about the tensile strength of human skin.
And here you thought this blog post would be boring!
"Tensile strength" is the maximum stress something can bear before breaking. Steel has an ultimate density, or tensile strength, of 400-5,200... somethings? I didn't read that closely. Human skin has a 20. Human hair is 380, while spider silk is 1000. Wow. Clothing has a tensile strength of about 6.
So human skin is actually relatively weak -- only three times as strong as clothing, and 1/19th as strong as human hair. A ping could, as I guessed, pass easily through the human skin.
Along the way, I saw -- don't get jealous of me that I spent time on a Friday night reading about this stuff! -- that there are materials with phenomenal tensile strengths. There's something called "Zylon" that's used in the Mars rovers that has a strength of 5800, while something called a "Boron Nitride nanotube" has a tensile strength of 33,000. So my ping projectiles could be made of something like that -- or coated in that, perhaps. And they'd pass through anything with a tensile strength of 20 or less.
So: Boron Nitride pings 6 times as strong as steel would pass through human skin pretty easily. What about the part where they don't come back out? It's possible, I suppose, that passing through the skin the first time would then reduce the momentum enough that the projectile couldn't pass back through on the way out. Since the momentum remains constant in a system except for friction, etc., the friction of passing through the organic material might slow it enough that it then wouldn't have the power to slice back out of the body on the other side.
But that doesn't seem very satisfying -- it would have to be slowed a lot to not be able to break back through the human skin, but still rebound over and over inside whatever part of the body it'd gotten into.
The resistance inside the human body isn't the problem: Organs are even weaker than skin. That's what I found out while I skimmed through papers and studies that contained phrases like "some interesting facts concerning the changes in meat during postmortem aging have been reported." I'd never heard that before. Isn't it just like Big Media to cover up the interesting facts about postmortem changes in meat? I'm glad I could help blow the lid off that cover-up. The liver has a very low tensile strength compared to human skin -- they measure it in kPA, or kilopascals, as opposed to MPa, or megapascals, for human skin. (I know this because I looked up a study on the biomechanical response of the human liver, where if I read it correctly some doctors smashed bits of liver against things.)
Muscle has a higher tensile strength, as much as maybe 100 according to a blurb I kind of read on one of the Google results. (Look, this isn't Science, with a capital S. It's 'science.' I'm going to skim.) So Which posed a different problem as soon as I realized it: it's not the skin that's the problem. The ping has to get through the muscle. So it'll easily pass through the skin if it can be fast enough to break through the tougher muscle, but there's still the problem of why it doesn't just shoot through like a regular bullet.
Here's where I'm really going to get in over my head with this stuff. If the pings were covered with a nanopin film, it might provide the bounce I need once it's inside: a nanopin film is a composite material that creates a hydrophobic effect sufficient to almost completely keep water from resting on it:
That's a picture of a lotus leaf, but the effect is similar: a water droplet landing on a nanopin film forms an almost-spherical shape rather than spreading out.
So here's how I'm going to misapply that: If the ping was covered in the tiny nanopin film, the additional repulsion provided by the hydrophobic qualities of the film might be enough to cause it to ricochet back off the inside of the skin, where there's more liquid than outside: the ping enters through the (relatively) dry outside, slows a bit, and then regains momentum by the repulsion of the hydrophobic coating versus the inside, wetter part of your skin. The projectile then still rebounds off bone, and goes through organs because even though they're wet, too, they're so much less dense/strong than skin it doesn't matter.
I realize this all has about the same validity of The Atom's 'belt made of white dwarf star material' allowing him to shrink
but I like it anyway.
And, frankly, if a dry, scientific discussion of tensile strengths and conservation of momentum won't get you to buy my book, then I don't know what will.