The science of fantasy creatures

Posted on February 22, 2011 (Subscribe to Blog)

As I make progress with Lake of Spirits (I'm now starting chapter eight) I'm reminded again of how bizarre creatures from myth and legend really are. Not just bizarre, but downright mind-boggling. How did these creatures come about? We know they never really existed, but why do we even entertain the idea of these things in stories?

I suppose the reason we "accept" them is because they're sort of fun and cool. That's why I write about them. But even as I'm writing about them, I'm questioning how one half of an animal can inexplicably be joined to something entirely different, defying biology with no ill effects.

Take, for example, the griffin – part eagle and part lion. Its head and front legs, along with its wings, belong to a giant eagle, while the back half belongs to a lion. Talons and feathers at the front, claws and fur at the back. The size of the eagle portion perfectly matches the lion, so it's an oversized eagle we're talking about here. Still, I'm not convinced that those wings, however large, would get the weight of that lion-butt off the ground.

There's a myth that says, "According to science, it's aerodynamically impossible for a bumblebee to fly." This myth was probably invented because of an overly simplified "linear treatment of oscillating aerofoils," where scientists clearly didn't take into account "dynamic stall in every oscillation cycle." It's obvious, when you think about it. Bumblebees can fly perfectly well, thank you. But most fantasy creatures really are aerodynamically unable to fly.

If a griffin was the size of a gnat, maybe it would be okay. Then perhaps the "dynamic stall in every oscillation cycle" would kick in. The laws of physics say that things work differently in the insect world, that their tiny sizes give them strength and abilities we mammals can only dream about. We've all heard that fleas are good at jumping, and it's true, everybody knows they can leap over a foot. Hmm, by that I mean they can leap more than twelve inches, not hurdle someone's boot, although maybe it amounts to the same thing. In any case, that's about the same as a human bounding over two football fields, or as high as a 100-floor building. Pretty impressive even by insects' standards... but if a flea was magically grown to the size of a human, don't expect it to perform the aforementioned leaps across football fields, because it could never happen.

But WHY? I hear some of you screaming (while the rest of you roll your eyes). Why can't a giant flea leap across town? It would happen in a movie, wouldn't it? Well, yes, but movies are utterly wrong. Take a small sugar cube. To make it twice as big, you have to double its height, width and depth, which works out to the equivalent of eight cubes stacked together. So a cube that's twice as big in linear terms (2 x 2 x 2) is eight times the volume and therefore eight times the weight. Likewise, a cube that's three times bigger is going to be twenty-seven times the weight (3 x 3 x 3), and so on. A flea that grows to twice its size must be eight times heavier, so its legs are not going to work quite as well. If it grows to a thousand times bigger – up from a millimeter to a full meter in length – then it's going to be a ridiculous billion times heavier (at least to Americans; it's a mere thousand million times bigger if you use the more sensible European numbering system).

Clearly resizing a bug like this isn't going to work. Its legs would snap. Think of a pond skater (or water strider), a small long-legged bug that stands on the skin of the water. It wouldn't be able to stand on the skin of the water if it were the size of a dog. If you dropped a 10-inch lizard from a height of ten inches, it would just get up and run away. But if you dropped a 100-foot lizard from a height of a hundred feet, it would splatter into goo. Size really does matter, you know. As a kid I wondered why a real-life car crumples easily at the front when it crashes into a wall, while my little toy car survived intact even when thrown with force, amounting to a scaled speed of hundreds of miles an hour.

This started me thinking (again) about Abigail, who as you may know is a faerie. She grows faerie wings and buzzes around, but actually her full transformation includes downsizing to the size of a hand – the true faerie size. So if that's true, and her faerie wings are designed to carry her around while she's no taller than six inches, then how can she fly while at full human height?

Well, I have a few answers, which I'll explore in Lake of Spirits. I'm pretty certain I won't be able to explain fully enough to satisfy physicists, but a smattering of "unknown magic" usually gets writers out of tight spots. One thing that's interesting to note, though, is what happens when you take a "normal" human girl of around five feet tall and 100 lbs (or 1600 ozs), and reduce her to six inches. That's ten times smaller, which works out at a thousand times lighter. So she goes from 1600 ounces down to a mere 1.6 ounces. Sounds about right, if you imagine a six-inch faerie standing on a set of scales. So her wings at this tiny faerie size don't have much work to do. Yet Abigail, even at five feet tall, manages to buzz around quite easily...

This is why a sprinkling of magic dust really, really helps.

Apparently humans put about fifteen times their body weight on their knees when they run. Many animals put on a hundred times their body weight – think of cats leaping down from fences. If you increase a human's physical size with the use of a magic wand, he only needs to be three times taller and already he's unable to stand up on those weak, feeble legs. That is, if everything else remains relative – muscles, bone density, etc. But an ogre evolved to be at least three times taller than humans, so I can easily get away with having Robbie transform into one; it's just a natural part of the transformation. The same can be said of Hal, Fenton, and others. But Abigail is an anomaly because she should be the size of a hand.

There's a lot more to it than just weight, but if you're really interested, you could read this brilliant article by a physicist about The Biology of B-Movie Monsters. You'll never see King Kong in the same light again.

But I digressed somewhere along the way. I was going to say that it's weird how halves of animals can be simply thrown together and, apparently, that's enough for the creature to become an "acceptable myth." Emily is a naga – a snake body with a human head. Does this mean she's a cold-blooded reptile with a warm-blooded head? How does that work, exactly? Poor Miss Simone is half fish! And I couldn't help wondering about Dewey, the centaur. Strictly speaking, this isn't a half-and-half creature. This is a half-human joined to a more-than-half-horse. The horse section is basically missing its head and neck, but the rest is intact – so does this mean centaurs have two hearts? I like to think they do, as well as two pairs of lungs and so on. Maybe the human-equine insides are all joined up in a mysterious but biologically sound way. Perhaps there's just one stomach, though; the centaur eats food with its human mouth, and the food is digested throughout the length of its body and finally passed through – er, well, anyway, you get the idea.

This is the tip of the iceberg when you really stop and think about it, but I've gone on long enough. I was going to start on about shapeshifters and what happens to, say, Hal when he eats a meal while in his dragon form and then reverts to human. Does the undigested food stay the same size...? Yeesh.

Pass the magic dust, someone.

After all this, it seems that the most normal, logical, and credible fantasy creatures are dragons!

Comment by MING on Tuesday, February 22, 2011...

Emily's not all mammal... she's part mammal, part reptile! No better off than Miss Simone - she's part fish, part mammal. Hmm, it makes sense when you say centaurs have two pairs of lungs; a centaur has its horse-lungs just below where the human torso joins the horse body.

Comment by KEITH ROBINSON on Tuesday, February 22, 2011...

Whoops! You're right, of course — I've now corrected my post. That was a deliberate error to see if you were awake, Ming. :-)

Comment by BRIAN B on Tuesday, February 22, 2011...

Fun piece. It just goes to show though...extraordinary claims require extraordinary evidence! Or else it's just magic!

Comment by STEVE MCCANN on Sunday, February 3, 2013...

Another thing about shape shifting in science fiction (not so much fantasy) is accounting for the conservation of matter and energy. If someone shape shifts into a gnat, where does all the extra matter go? Conversely, if someone shape shifts into an elephant, where do they obtain the extra mass?

I also can't help but wonder about the tremendous energy needed to create these massive changes. Think of all the heat liberated and the resulting deluge of sweat after a person sprints across a football field, converting glucose into energy. I would think simply changing ones face to resemble somebody else would generate enough heat to cook that person to a crisp.

Of course, in fantasy, it's all good because of magic. Still, I find limiting the possibilities of magic forces a writer to be more inventive and create a more interesting story.

Comment by CARYS on Saturday, July 19, 2014...

... Wow. I'm now going to be up all night (and every night, for the next week) thinking about this! Isn't it weird that people just kind of accept these abnormal creatures?

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