can humans fly like birds

Surely, humans have tried to make this work. It seems like it could work. Unfortunately, I think we are doomed to remain as ground-based animals. Well, that is unless you count powered flight or gliding. We can do both of those.

Then why not? Perhaps the simplest answer is we are too big. Oh, too big you say? Well, surely we arent too big. Maybe if we just had bigger wings, it would work. Nope. It wont work (well, probably wont work). This falls into a category of things called stuff that doesnt scale like your intuition. Or perhaps I should say bigger things arent the same as smaller things.

Now for my super short calculation hopefully to be followed by some useful data. Let me represent the muscle of an animal as the following cylinder.

So, the diameter is 2r with a height of h. Let me further suppose that the strength of this muscle is proportional to the cross sectional area (not strictly true but just hold on) and the weight is proportional to the volume of the cylinder. This would give a strength to weight ratio of:

Here, C is just some constant. But what matters more is the result. If I make an animal twice as tall and scale the rest of the dimensions proportionately, r would double and so would h. But the strength to weight ratio would be half as much as the smaller animal. Ok, well I can fix that. Let me double the mass (volume) but keep the same strength to weight ratio. I would need the same height, and the radius would have to be sqrt(2) times larger. Here is what that would look like.

Perhaps you can start to see the problem. Even though this muscle model is completely made up, it still shows a problem. Bigger things get heavier way faster than they get stronger. This is also why my 8 year old daughter can do more pull ups than I can. She thinks shes tough, but can she drive a car? No.

Back to flying. I suspect that humans are at that size where it would just be super-awkward to have a body build suitable for flying. Perhaps this is also why you dont see giant birds.

How about I look at some birds that fly. You might also think of the giant flying dinosaurs (that arent actually dinosaurs) like the pterosaurs. The largest of these was perhaps the quetzalcoatlus. According to Wikipedia, it seems the size is not universally agreed on. It perhaps had a 35 foot wingspan and a mass anywhere from 70 -200 kg (150 440 lbs).

Did it actually fly? Who knows. Maybe it just glided. Maybe it was just big and didnt fly. Perhaps we will never know for sure until will complete our time machine.

Well, then what about a bird we know for sure can fly. A real bird that exists now. How about the Wandering Albatross? Well, at least it is the largest living flying bird according to Wikipedia. If its on Wikipedia, it has to be true, right?

Here is the plan. Let me look at a whole bunch of birds and see if there is a correlation between mass and wingspan. Here we go. Almost all of this data has been scraped from Wikipedia. I started with this page on Wikipedia and just followed links almost at random. Not all bird-wikipedia pages are alike. Some list wingspan, some dont.

Well, that turned out a little bit better than I expected. But what next? It would be nice if I could fit some function to this data. I could just start guessing functions to see what works, or I could see what makes sense. The data actually look parabolic. This would suggest a function something like:

Where w is the wingspan, m is the mass and C is some constant. This isnt really what I would have expected, but I will run with it. In order to find the constant C, I will plot w2 vs. the mass. This should be a linear function and I can find the slope. Here is that plot.

This fit gives a slope of 0.64 m2/kg and a intercept of 0.62 m2. It looks nice except it doesnt seem to fit very well with the smaller mass birds. I could probably get a better function, but this will do for now.

This fit gives a slope of 0. 64 m2/kg and a intercept of 0. 62 m2. Although it seems to fit poorly with the smaller mass birds, it still has a nice appearance. Though I could probably get a better function, for the time being this will do.

That worked out a little bit better than I had anticipated, though. I would like to fit some function to this data, but what comes next? I could just begin speculating on functions to see what functions, or I could look for patterns. The data actually look parabolic. This would suggest a function something like:

You see the issue? I could keep playing this game until I find wings that would work. The issue is that it will be difficult to fit wings that are seven meters long inside your car. And that is why humans cant fly.

When Daedalus launched on April 23, 1988, it was driven by 160-pound Olympic cyclist Kanellos Kanellopoulos from the Greek island of Crete. After encountering strong winds that harmed the craft’s tail boom, Daedalus crashed into the waves three hours, four minutes, and fifty-nine seconds later, close to the black sand beaches of Santorini. Kanellopoulos swam ashore, and the Daedalus, having flown 72. 4 miles, smashed the worlds record for human-powered flight. This human-powered aircraft will never fly again, but it still serves as an inspiration in its current location at Dulles Airport’s Terminal B. [contact-form-7 id=”442″ title=”Submit Question”].

Furthermore, Drela says it’s unlikely that humans will be able to fly by flapping wings with the help of our legs. Human legs are theoretically strong enough to accomplish this, but only if the wings are sufficiently large at least 80 feet or so and if they also weigh a significant amount less than a human. With current mechanical technology, achieving this large-size/low-weight combination is very difficult, and despite many attempts, no one has ever succeeded or even come close to realizing it.

However, according to Drela, we have succeeded in one kind of human-powered flight, utilizing a fixed-wing aircraft with leg-pedaling propellers. The wing can be constructed to be long enough and light enough to allow flight because it is fixed. Around 100 airplanes like this have been flown to date. A noteworthy instance of this design is the Daedalus aircraft, which was created over the course of several years at MIT by Drela and other faculty and students. Daedalus, named for the legendary Greek inventor, is only 52 pounds in weight and has a wing span of 112 feet. When combined, the craft weighs only 68 pounds.

FAQ

Will humans ever be able to fly?

Virtually impossible. To even begin to evolve in that direction, our species would need to be subject to some sort of selective pressure that would favour the development of proto-wings, which we’re not.

Can humans fly if they had wings?

Even if humans did have wings, we wouldn’t immediately be able to fly. To fly, we would also need the right body size and metabolism. Metabolism is our body’s ability to use fuel (such as from the food we eat) to make energy, which helps us move. Birds have very higher metabolisms than us.

Can we make wings for humans?

Our musculoskeletal system is heavier than birds. We cannot support our weight and fly as the laws of physics will not let us do it. We cannot overcome gravity as we do not have certain organs or features to do it. We cannot even levitate as we fall under the universal laws of physics.

Can humans fly with insect wings?

A human is even larger than a bird, and thus cannot use either the butterfly’s wings or the bird’s wings to fly. Instead, we fly a different way – building machines that can use far more power than that of a bird’s wing.