# Chix In Space!January 8, 2015 3:16 PM   Subscribe

Could an ostrich fly on the moon? Expand that out, what flightless birds could fly on other celestial bodies? For that matter, what birds would be rendered flightless if they went to a different planet?

I was just watching Peg+Cat with my kids and the pig brings 100 chickens to the moon. And that got me to thinking. Could flightless birds on earth learn to be flightful birds on a different planet?
posted by Nanukthedog to Science & Nature (8 answers total)

It'd be pretty hard to fly at all on the moon given the lack of atmosphere. Or is your question solely about whether the force of gravity is reduced but all else (including air density at sea level) is constant?
posted by Aleyn at 3:20 PM on January 8, 2015

This What If column might be of interest, re: atmospheric conditions and gravity: What if you tried to fly an airplane on the other planets?
posted by LobsterMitten at 3:22 PM on January 8, 2015 [4 favorites]

For easier reading, here is a copy of the text of LobsterMitten's link with all aircraft-related words replaced with "penguin."

Sample excerpt: "Your penguin would fly pretty well, except it would be on fire the whole time, and then it would stop flying, and then stop being a penguin."
posted by contraption at 4:17 PM on January 8, 2015 [10 favorites]

Best answer: The male Great Bustard "is possibly the heaviest living flying animal"; specimens as large as 21kg have been collected. (wikipeda).

According to the identity F=MG, a 21kg bustard must generate about 200 newtons of force in order to successfully take off in earth's surface gravity of 9.8m/s^2. Assuming that in a big enclosed space on the moon at standard pressure the bustard could still generate the same 200 newtons of force, it could still take off if weights were added to it so that the total mass is 127kg. 127kg is above wikipedia's average mass of an ostrich.

All that said, there are several problems with imagining actual ostriches. The biggest is that ostrich feathers are no longer adapted to give lift in the way they are in a flighted bird species (plus other physical adaptations that probably include things like range of motion, strong vs weak muscles, etc); the second is that the flying motions are probably not instictive in living ostriches, since they have no use for it.

So while it's plausible that a bird massing as much as an ostrich could fly in a habitat on the moon, I don't think that an unmodified ostrich could be taken from the earth today and learn to fly.
posted by jepler at 4:43 PM on January 8, 2015 [2 favorites]

Best answer: In a thin enough atmosphere all birds are flightless. Also they would suffocate. In a really thick atmosphere I dunno what's that atmosphere made of? I guess we're thinking some oxygen and not much poison, and ... you know what, that's too complicated.

But in a pressurized dome full of earth-like air at earth-like pressures: Certainly as gravity goes up things that can fly now will become unable to fly. Which are grounded first will depend on how much extra power they have available. This documents a inverse correlation between climbing speed and weight. So basically little birds fare better in high gravity environments. Swifts particularly have been seen with have very rapid ascents.

It's really hard to predict how little gravity you'd need before chickens would gain the ability to fly. For one thing, they haven't really been developing those muscles over their lives. Chickens aren't so dissimilar from flighted birds, so I do think with low enough gravity (pluto?) they might have a chance, not only of mechanically pulling it off, but also of instinctively figuring out what to do to make it happen. I'm not sure how light the gravity would need to be, though I think "chickens" are varied enough in size and weight that there's not one single answer.

I don't see how the ratites (ostriches, emus, cassowaries, etc) have much flight advantages over mammals. They're quite heavy (ostriches can weigh over 300 pounds!). Also, they lack preen glands, which is how normal birds make the preen oil that holds their feathers together. This is why they look permanently comically disheveled, but I think this would very much reduce their feathers effectiveness at pushing air around. Their wings aren't particularly well structured for that either, and I have no idea if they'd be able to figure out what to do with them. So in conclusion: I don't think you could make a gravity low enough that ostriches would really be flying. At some point they could just push off of walls and float, like the humans in ISS do.

The aquatic flightless birds do have preen glands, but their wings are really small, and they're not at all light either. They at least know how to swim through a medium, but again, I don't think there's much hope for them really successfully flying.
posted by aubilenon at 4:44 PM on January 8, 2015 [4 favorites]

Chickens can fly. They just can't fly for very long.
posted by musofire at 6:55 PM on January 8, 2015

Flight is about generating lift. Given an atmosphere, everything can generate lift. You yourself can generate lift right this moment by running and flapping your arms. But you can't fly because you don't have the muscle power and lifting surface area to generate enough lift in our relatively thin atmosphere to counteract gravity.

What flightless birds could fly on other celestial bodies? All of them. They could all fly, given the right conditions. Less gravity, a thicker atmosphere. They could all fly. So could you.
posted by Cool Papa Bell at 10:25 PM on January 8, 2015 [3 favorites]

What an interesting question. Whether they can fly or not, wouldn't it be cool to see a video of an ostrich "running" on the moon in those great, big, slow-motion hops that the astronauts did?
posted by CathyG at 8:31 AM on January 9, 2015

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