Also… Imma have to run the math, here. Because I forgot how bone density is affected by age.
 
Okay, so bone density lessens through puberty, meaning this could be a difference in age, rather than race.

Ah, the wonders of injecting small bits of real-world logic into a fantasy show for those willing to notice.

This makes sense because much like a bird, it’s important that the bones must be light enough so the wings can provide enough lift to overcome the gravity.

 
That would make sense.

@Daneasaur  
This.

I still say that the “cloud” and “apple” bone are in fact solid magic organs which allows the ponies to process their innate magic abilities.

@CyanLightning  
Technically physics in this case, but true. I’ve actually made up an explanation for magic that uses physics to explain it, but it’s full of holes.

@Eeveeinheat  
Clarke’s third law
 
Any sufficiently advanced technology is indistinguishable from magic.

@CyanLightning  
My point isn’t to say ‘magic done did it’ but that it literally has to be magic providing the lift, otherwise it is impossible. And in my mind magic has rules, even if we don’t know it. It would be better to argue about the mechanics of said magic, instead of two equally impossible sides.

@Eeveeinheat  
You know it’s not fun for just accepting that everything that odd happened in the show is is always about magic or lazy writing, while yeah it is useless to arguing that, but sometimes do something useless is fun.

Are people really talking about the physics of obviously magical flight as if it were anything other than magic generating the lift?

@Background Pony #42F3  
So bye i guess.

@CyanLightning  
Well, whatever. I don’t at all agree with the whole ‘less gravity’ idea, but I’m done arguing for now, I’ve already made my points and I’m tired.

@Background Pony #42F3  
like i say before this sort of argument is basically useless, also where does the those big creature got their food i mean there is a lot of big creature in equestria. but still 10-15 % decrease in gravity will not going to be noticeable by our perception and it going to make a lot of different in the field, but Hey it’s still useless to arguing something like this.

@CyanLightning  
Less gravity? Nah, no way. That sort of thing is extremely significant and would make itself totally obvious in the show, especially at this point in the series, with far reaching effects and implications on all sorts of things, and that’s a severe understatement I’d imagine. It’s pretty darn safe to say that they have the same level of gravity as us.
 
You are right that the show is not likely to go into any detail on any of this stuff, though.

You know people this isn’t just about the wing span or energy that put to the wing to fly, but also this is about the gravity that equestria have, probably equstria have less gravity than earth, but why did dinosaur were exist in earth, well it probably because of the structure in their body that allow a lot of air enter to their body, so it decrease their body mass and increase their body surface to the body mass ratio. But it come with cost, they aren’t really able to control their body temperature and probably the thing that lead to their extinction, because after the the asteroid impact, the earth become cooler, and this can apply to the dragon and anything that have large body in equestria and the reason why dragon live in the volcanic area because it can maintain their body temperature.
 
So yeah less gravity mean less force needed for pegasus to fly and less wing span need. But here’s the thing if their gravity are weaker than earth. why the atmosphere haven’t been blown away by solar wind just like mars. well it probably that they have less active sun or smaller sun or their sun isn’t the sun at all but just a magical ball floating in the space, but hey it’s very hard to make sense something in the cartoon, because they are using cartoon physic that can disobey any known law of physic for the sake of the plot.

@TheDeinonychus  
Well, it’s darn clear that pegasi don’t fly anything like hummingbirds or bees do, not even close. The pegasi seem to be able to flap their wings at a relatively relaxed or calm pace and still hover stably and comfortably or fly at a normal speed. With that in mind, I think I’m just gonna stick by my argument that they’re assisted with flying to some extent or another by magic or something.
 
Anyway, I guess I could say more, but that’s enough of this discussion for me. So at least for now, I’ll be going. May reply, but I’m feeling a bit exhausted and stressed today.

@Wiimeiser  
It’s not about the size of the wingspan, per say, so much as it is how much force those wings can apply. With enough force, you can lift and move nearly any object. This is why a rocket or missile can fly even without wings (those that do actually use them only for stabilization, not lift). For something with fixed wings (such as aircraft) this is usually done by giving them a more powerful engine. With non-fixed wing flight (such as with birds, insects, and pegasi), this force must be applied by the wings themselves. This is where you get into the ‘infinite paradox’ you described. More force means larger wings, which means more muscles to power said wings, which means more weight, which means more force needed to reach flight.
 
You can usually avoid this paradox by changing either the wings themselves or the way they move. Humming birds and bumblebees are good examples of how changing the way the force is generated allows a creature to fly without falling into that paradox.
 
Of course, this is all a bit too complex to really be expressed in a kid’s cartoon XD

@Background Pony #42F3  
In order for a human to be able to fly, our wingspan would need to be 1.2x the length of the largest known wingspan ever recorded, which is just above the threshold of the point where the needed increase in required cardiac strength would lead to an infinite paradox (as in, there are two men, each taller than the other)

Yay for inconsistency, and wing bones… and ear bones, apparently. And that… apple bone? And a cloud bone? Frankly, this is absurd.

@TheDeinonychus  
It is based on a human, but I can’t imagine the difference being much for the ponies in MLP.
 
Anyway, I never said the pegasi use nothing but magic to fly, there’s obviously an even bigger physical aspect to it, hence ponies doing physical training to get better at it. I just said that I think magic assisted them to some extent. Such as in the many situations where pegasi hover in place with a relatively relaxed/calm wing flapping pace.
 
Their wings in the show are seemingly small enough that even with lighter bones, it likely wouldn’t be enough on their own. But who knows. I do know there’s plenty of reason to assume the ponies (and other sapient species in MLP, too) have some forms of innate magic though, so it’s certainly not outside the realm of possibility either way.
 
Of course, you could easily argue the wings in the show are to some extent or another ‘stylized’ and would be bigger in reality, which also seems fairly likely. Though, there’s definitely no reason magic couldn’t still help things along even then, especially with stuff like the whole hovering in place. I’d imagine it would, even if the physical component is the primary factor.

@Background Pony #42F3  
Is that 10% based on a human skeleton? Cause I’m willing to bet the percentage is much different for different animals.
 
Also, unless you’re willing to also claim that pegasi and unicorns were magically created, using magic to explain their flight is only a partial answer. If their flight was magical in nature, then why have wings in the first place? They could simply levitate around the same way Starlight Glimmer did. We also know that a pegasus with an injured or bound wing can’t fly, so it’s clear that their wings do play a major part in their ability to fly.

@Outcast’s Redeemer  
I don’t really agree with the whole “pegasi have light bones” idea, but I’ve already gone through that in an above comment. Could say more, but I don’t particularly want to get into it. Not that the overall weight difference would be huge either way, as bones only make up about 10%~ of body weight.
 
Anyway, I will stress that regardless of what you choose to headcanon about bones, it’s pretty clear the pegasi aren’t more prone to injury or anything. They seem just as sturdy as the other pony types.