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
One of the heaviest birds to have ever lived weighed as much as a human. It had a 6m wing span.
[https://en.wikipedia.org/wiki/Argentavis](https://en.wikipedia.org/wiki/Argentavis)
You would need an enormous amount of effort to flap 6m of even the best designed wings (and they would need to be very light and have an extreme amount of flexible movement and control – even accurate and ever-changing feather orientation is required to have a bird be able to fly properly).
“It has been estimated that the minimal velocity for the wing of A. magnificens is about 11 metres per second (36 ft/s) or 40 kilometres per hour (25 mph). Especially for takeoff, it would have depended on the wind. Although its legs were strong enough to provide it with a running or jumping start, the wings were simply too long to flap effectively until the bird was some height off the ground. However, skeletal evidence suggests that its breast muscles were not powerful enough for wing flapping for extended periods. Argentavis may have used mountain slopes and headwinds to take off.”
So if you can carry a 6m set of wings, had perfect and trained control over their movement, were able to flap and run up to 25mph and were prepared to jump off a cliff to start it, you might be able to glide like they probably spend most of their flight doing.
I wouldn’t recommend it, though, because weight-for-weight such a bird would have far, far, far stronger and faster muscles than you would have, even if it was the same weight as you, and spent its life from a tiny bird learning how to fly and not putting on weight (which would ground it immediately). They would have hollow bones, most likely, much of their weight would be accounted for by 6m of muscular wings (so we could chop your arms and half your legs off if you like, and then used the saved weight to give you a pair of wings, to keep the weights about even), and then you’d have to flap them JUST right, fast enough and hard enough to literally pull yourself off the ground against gravity.
I recommend you try it before you throw yourself off a cliff reliant on being able to fly your way out of danger. People did. For decades. Centuries even. Humans don’t really have the musculature to do it and the technique takes extreme amounts of energy and skill to do (it’s not just a case of flapping or gliding).
Pretty much, anyone who has ever tried has been unable to even get higher than they could have jumped without the wings, and never for longer than gravity takes to pull them back to earth.
The largest birds ever to have lived, with musculature far in excess of our own, wingspans that you literally couldn’t fit in most rooms (even with the wings dropped to the floor because you’re only going to be about 1.7-2m tall at most), with highly optimised and light bodies for their strength, all their strength in their wings and tiny, tiny thin and light legs and brains and bodies, weighing roughly what a human alone would weigh, throwing themselves off a cliff, with a lifetime of experience, getting up to 25mph (a near-fatal speed even in a car-pedestrian collision!) in order to be able to do some small piece of light flight for non-extended periods of time.
And even with all the modern tech a hang-glider can’t “flap” properly to increase height, the technology to do so would weigh more than the wing itself. All we can do is glide. And hang-gliders tend to have 10m wingspans or thereabouts in order to support the weight of a human and themselves in an upward draft of warm air.
If you got a kid, trained them from birth to bulk up their arms to become immensely strong (like gorilla-strong), never let them build up their legs or lungs or brain, kept them quite small and light in every respect, gave them a 6m wingspan, had a technological arrangement that you could modify the entire shape of the wing easily without any extra weight, got them to practice it every day from birth, you may be able to get them to lift off the ground for short periods.
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