The merchant wanted me to clear the decaying tomb outside the village. I was halfway to it when I saw something more interesting in the distance. It was a set of stairs carved into stone that instantly distracted me, like a million other little things in Skyrim, from my quest. I set out for the stairs and made my way up a few before a troll beset me. It got too close. With three words and a mighty shout, a blast of air blew the troll down the mountainside like a smelly ragdoll no child would buy. Above me, a dragon roared. I felt powerful. Could you do something like that for real?
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Dragons are on my mind, dragons and the power of breath. Recently I tried to make some sense out of fire-breathing dragons and while doing so my mind wandered to the epic RPG, Skyrim. With a save file totaling more than 90 hours of dungeon crawling, potion crafting, and dragon slaying, the magic of Skyrim is as ingrained in me as the myth of dragons themselves. In the game, what unites your character to these monstrosities is your voice, your “thu’um.” Your voice has the power to push walls of fire, ice, and concentrated momentum. This last thu’um—or “shout”—has even gained Internet memedom for its power. Fus Ro Dah!
There is an obscene pleasure in fus ro dah-ing a reanimated Norse skeleton into a deep glacial crevasse. Limbs fail and bodies tumble before your mighty voice. But since this is literally your voice pushing people around, momentum and physics can illuminate it as much as the constellations that unlock the skill inside the game can. What would it take to shout “fus ro dah” and knock a person over?
In my endless Internet stumbling, I came across a journal that looks to be authored by physics students and teachers who share my enthusiasm for nerdy topics. One of them must like Skyrim as much as I do, because this paper in the Journal of Physics Special Topics sought to answer the very question I was wondering about in-between reloading saves to make sure my Lydia wouldn’t be lost forever. The paper reads like a wonderful introduction to physics.
Like any good physics problem, figuring out the necessary power of a fus ro dah begins with making something very complicated very simple. First, assume that your target isn’t some oddly shaped humanoid, but a cube. Then make a few more assumptions. For the sake of calculation you need a mass of the target and a value for the friction between them and what they are standing on (this value will ultimately determine what force it will take to tip the cube/person over). With these numbers you draw the cube and do some torque-filled calculation—blowing someone over is like finding the amount of force you need to turn a person like a wheel about an axis. In this case, the axis is his or her heels.
All in all, the paper from the nerdy physicists concludes that it would take around 120 newtons applied to the center of an 84-kilogram person to tip them over—far less than you could generate with a punch. I suppose this scenario is like being caught off-guard by a strong draft. Still, could the human voice bring with it this windy punch?
More assumptions are required. If you multiply an assumed amount of air exhaled by the average human by the density of air at normal temperature and pressure, you get the mass of a shout. And because you are shouting at an opponent, the speed of this Thu’um should be the speed of sound—over 300 meters per second. Mass and velocity together describe momentum. The last value needed is time of impact, something small like 0.1 seconds. Finally, if you take the change in the Thu’um’s momentum over the impact time you get a force. It’s tiny, only about four newtons, or barely three percent of what is needed to tip an attacker over. The underwhelming result at least makes intuitive sense. Even when you shout at the top of your lungs, you don’t feel as if you are marshaling much momentum. You can hardly blow out a candle at distance.
Skyrim is a game filled with fantasy, and physics dictates that some is needed to make the fus ro dah as powerful as it is in the game. In the final, geeky paragraphs of the paper, the authors calculate the volume of air and/or the air speed your lungs would really need to push an enemy over. If the volume of the lungs remained quite human, one would have to shout at Mach 32—air escaping your mouth almost fast enough to leave Earth’s gravity. But if your shout’s speed remained underwhelming, you would have to exhale 19 liters worth of air to deliver the knockout blow. You lungs at maximum inflation hold about four.
No matter how you shift the variables around, the human body just isn’t the air cannon Skyrim’s Dovahkiin is. Following the physics, the most yelling “Fus Ro Dah!” at an enemy will get you is a slight pause and a very confused look.
More Geeky Science:
- The Many-Worlds Hypothesis And The Hardest Super Mario Level
- ‘The Walking Dead’ Zombie Virus Makes More Sense As Venom
Reference: East, O., Longstaff, E., Fletcher, M., & Li, C. (2013, November 6). Fus Ro Dah. Journal of Physics Special Topics. (http://physics.le.ac.uk/journals/index.php/pst/article/view/663)