eli5: Why is it not possible to build bird-like attachable wings that account for body proportions to allow humans to fly or glide around?
In: 2102
You totally could! You could absolutely attach bird wings to a person that they could fly or glide around in.
But unfortunately, humans are heavy. The wings would need to be at least maybe 22 feet across to work. But 22 foot wings that can keep a person aloft are really heavy to flap. You basically need to push your weight worth of air downwards, like a pushup except repeatedly. Human arms don’t have that.
The reason this scales so poorly is because of this idea called the “square-cube law.” The idea is that, when you scale an object up N times, the surface area of a thing gets N*N times bigger, but the volume of a thing gets N*N*N times bigger. Think about a cube that’s 1 foot across. The front of that cube is 1 foot by 1 foot, 1 square foot. Scale the cube up so every side is 2 feet across, and now the front is now 2 feet by 2 feet, which is 4 square feet. But the volume of the original cube went from 1*1*1=1 cubic foot to 2*2*2=8 cubic feet. Your weight comes from your volume. A wing’s ability to fly comes partly from its surface area. What’s that mean? Well, it means kaiju don’t really work, but it also means that if you scale up a small bird, it probably won’t be able to fly either.
But don’t let that bother you, we’re not limited by biology. We have science. You can strap bird-like attachable wings on today and glide around. That’s a hang glider.
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