There are no hard and fast rules for giant physics because the situation is entirely up to interpretation, and to draw from other things in nature takes some patchworking that still results in estimation. However, in storytelling, I believe there are ways to go about it that just make sense.
Gulliver’s Travels is probably the only work of literature in existence that goes into great detail about the giant/tiny experience. Every move Gulliver makes in Lilliput, for example, is almost always overpowering for the Lilliputians. His normal speaking voice is too loud, clapping can bring a crowd to its knees, and even a sneeze can blow a man off his feet like a leaf in the wind. To that end, I’m really surprised Swift didn’t say much about the ground shake when Gulliver walks or sits. (That’s my favorite part! That’s why I’m always pointing it out in my books. The ultimate expression of passive power, as it were.) Perhaps all that was for effect, to show Gulliver’s physical superiority to the Lilliputians, but not under any sense of realism. But if your goal is like mine, in that you want to shed an inviting light on interaction with giants, there are some things you just have to de-emphasize. Let’s take a look at how I’ve handled some of those things in my own giant-handling.
Of all the sensory input of giantdom, sound is the one Swift harps on the most. In Lilliput, Gulliver has to whisper all the time and has trouble hearing the Lilliputians if they are not shouting or otherwise speaking directly into his ear. In Brobdingnag, where he is the only tiny person among giants, Gulliver complains incessantly about the noise level and describes being exhausted from shouting to be heard. Is there any realism to that? We’ll never know for sure because we don’t have giants that size around, nor tiny people to tell us how annoying we are. But, in my estimation, the sound would not be that bad. A good example is in The Harp Effect, where the giants and smaller people are on that same 1/12 scale that Jonathan Swift uses both in Lilliput and Brobdingnag. An average adult male giant is roughly 72 ft. tall or close to it, give or take a few feet (6 ft. tall to their own).
Can giants hear little people without having them shout? On this scale, yes. If you, giant, are sitting next to someone on the ground who is about 5-6 inches tall to you, I don’t think you’re going to have trouble hearing their normal speaking voice at a distance of your hip. Put your hand there. Yes, right now. If you’re an adult, your hand is probably about 6 inches long. It’s not that far from your ears, is it? Now, if the little person next to you is whispering to a friend, you will certainly miss that conversation without doing some very noticeable eavesdropping. Everything else, you’ll be able to hear just fine.
In Greater Perspective, I admit that I fudged on this. A three inch tall person would be quite difficult to hear in most situations without requiring them to shout, yet the giants very seldom raise Celeste to their ears. Because Celeste is often in a three-way conversation with her giants, or conversations where a giant other than the one holding her will interject, I waived the concept for ease of scene flow.
How about standing? Yes, if you are standing below a 72 ft. giant who is also standing at full height, you will probably have to shout to be coherent. At the feet of the Greater Perspective gang…just forget it. You’d better have another way of getting their attention from the ground.
Are giant voices too loud for the ears of tiny people? This is a little more realistic. My answer is “maybe.” The bottom line for focal giant characters, though, is that, if they’re unbearable to listen to or to be around, that’s not going to make them very endearing characters. So, I’ve bent the rules of physics in both series to make your giant-viewing experience more relaxing. Although, I did give credence to their massiveness by making things like sudden laughter, shouting, cheering, forceful whistling, and clapping a momentary disturbance. For example, in Greater Perspective, 95 foot Derek, whose regular speaking voice is not abrasive on normal human ears, nearly takes out the crowd by whistling at Celeste and Vincent in a catcall manner. Overall, while it is the law of giant etiquette to speak in a mild volume around little folk, I don’t think whispering is necessary.
Probably the single most exaggerated act of giantry in film is the sneeze. With comical, hurricane force, it blows all objects and furniture to the other side of the room, or uproots vegetation and farmhouses. “Myth Busters” time. Would a giant sneeze realistically knock down a tiny person at close range? Hopefully, your giant friends have enough self-control and politeness to turn away from you when they must sneeze, but, for the sake of giant science, we’ll say that you were subject to a dry blast. On a flat, stable surface, the force packed by a giant’s sneeze would likely cause you to stagger backward, but not fly across the room, or even a couple feet from where you were standing. The air would rush past you like a sudden gust of storm-force wind, lasting about one second (and, hopefully, it’s all wind and no rain, if you know what I mean).
Derek, of Greater Perspective, and I were chatting one day during production and he asked facetiously why giants seem to be relegated to moving in slow motion. They don’t. But I contend you can look awesome while doing it. I was once watching a historical documentary where, during the voice-over and dramatic music, certain characters would approach the camera in slow motion. My father humorously said, “It must mean they’re important.” So, let’s go with that, Derek.
Now for the good part. Ground shake. It’s the first indication that a giant is near. There’s a running joke in my casts that giants never have any stealth simply because of that. (I have to say, though, that Disney’s new BFG has some skillz!)
So, from how far away does ground shake effect the environment of the onlooker? It’s a question I’ve spent a lot of time on. But, because I don’t have access to a physics lab and a few tons of stuff, I usually go for what works for suspenseful effect in the story. When reality is not good enough, just make it feel good. That goes for anything story. I implement shake where I need shake, but try to give it some realistic progression. Naturally, shake is minimal, at first, and will increase as the giant nears, the rate and intensity of which will all depend on the speed, size, and even character of your giant. Jurassic Park, the movie, executed the suspense beautifully with the recurring use of ripples in a glass of water.
While the quake is progressing, I love to use that time to double the suspense by going inside my diminutive character’s head and explore their thoughts – maybe even fears – on the situation. As much as I love giants, some do feature as villains in my stories – and I love fearing them right along with my protagonists (who are actually not loving the fear like I am).
Giant shake is also something greatly exaggerated for effect in movies. In the movies, a giant’s every move is generally earth-shattering. And that’s neither practical nor realistic. Sitting or taking to knee on the ground (depending on how considerate your giant is), running, jumping, and falling are going to yield you some abrasive quakes, while general walking is much lighter than the cinema has lead you to believe. It depends on the objects in the environment to absorb the shock. In a city, where there are lots of little, moving parts, things are going to rattle significantly. Out in a field, the tremor may not be as noticeable. In my estimation, a giant on a stroll, with casual footfalls that don’t come very far off the ground, will not jar your environment until they’re right up on you. Before that point, you might get some rattling of your loose items and the walls. For greater and sustained shaking, your giant could be walking with purpose or making carelessly heavy impacts out of either apathy or naivety. If you want to get a sense for how to implement ground shake in a small, contained area, walk around in your own dining room or kitchen, or some place in your house where glass or metal is stored. Listen to how things rattle as you walk, run, sit, etc.
Ground shake is my favorite element of giantry not only because it’s exciting, but because of the thematic things you can do with it. I love the juxtaposition of great strength and power with innocence and gentleness of equal intensity. Bobby, one of the giant children in The Harp Effect and Princess Reaona’s best friend, is a great example. He is a 60 foot ten-year-old boy with lots of curiosity for the little folk, which is no comfort for some villagers. He knows that in order to maintain his visiting privileges among the little people who fascinate him so much, he must control his strength and distribution of weight. But, he’s not perfect. Still, if his fluffy, blonde hair, soft apology, and adorably sheepish smile doesn’t charm your pants right off, nothing will.
Another example is the never-before-seen giant/human relationship between Celeste Nortram and her boyfriend, Dr. Vincent Harcourt, the latter of whom becomes 103 feet tall in a genetic experiment that went awry (Greater Perspective). What they prove is that, despite Vincent’s capability to crush Celeste effortlessly by any means, even just a few fingers, which he initially fears, they still manage to be (safely) physically intimate with each other in unique, adaptive ways.
I always make a point to show off the power of my giants, even to the point of being overbearing at times for their tiny friends, in order to make their gentleness all the more amazing and impacting. Even since early elementary school, I’ve just had an innate sense for it.