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I am wondering if it is possible for whales to fly. I'm considering two different cases.
How could we alter earth conditions (thickness, gravity) so that whales could actively fly (without changing anything in the whales)?
How could we alter whales (changes in bones, physiology, anatomy, but leaving size and apperance untouched) so that tey could fly normally in Earth conditions?
High density atmosphere.
Whales can do what they do because they are neutrally buoyant. The water they are in buoys up their great mass and so they are weightless. They are not massless and so still must propel themselves around, but the great oppression of gravity is alleviated.
If the mass of a thing is less than the mass of the volume of atmosphere it displaces, that thing will float. True for a whale in water, true for a helium balloon in air. Let us assume whale-like whales, not some hydrogen balloon creatures which although awesome would be unwhalelike.
Venus has a high pressure atmosphere - 93 bar so about 93x our atmospheric pressure. But that still yields gas only about 5% the density of water so water things would not float in the gas.
What about Jupiter? Gas giant! There is some point in the atmosphere where it would be dense enough for whales to float? Yes, but apparently it is so hot at that depth that the whale would get cooked. This is covered in this xkcd. https://what-if.xkcd.com/138/ and at some depth in this WB stack answer. Is a moon floating on the atmosphere of a gas giant possible?
But you want flying whales and you shall have them! The problem with Jupiter is that its atmosphere is made of light stuff - hydrogen and helium. You really need to compress that stuff to make it as dense as water. Venus is better with CO2 atmosphere.
The trick is to make an atmosphere out of a very dense gas. I once proposed that a bubble of xenon at sufficient depth under the ocean would be denser than the water, and so exclude the water which would float on top.
from http://www.halfbakery.com/idea/Xenon_20Breathers
With every doubling of pressure, the weight of a given volume of gas doubles. The weight of a volume of water does not change with pressure. My math: 1 atm increase with 10 meters depth 1 liter H2O = 100 gm 22.4 liters water = 2240 gm 22.4 liters xenon at 1 atm = 52 gm 52x = 2240 x = 2240/52 = 43 atm or 430 meters So I figure that at 431 meters depth, a bubble of xenon will sink. Therefore a permanent subsea habitat could be made below 431 meters just by pumping a hole in the sea floor full of xenon. The xenon will not bubble out. You could access it by walking down some stairs.
430 meters below the ocean is not some unworldly life-destroying pressure. Lots of things live down there and much deeper. And to make it wilder, in your atmosphere you could include radon - yes it is radioactive but life adapts and it is even denser than xenon.
Lo - your flying whale! It lives in an atmosphere of very heavy noble gases. It filter feeds on the flying radioautotrophs which get their energy harnessing the radiation of atmospheric radon .
For the skeptics - Cody of Cody's lab demonstrated the above described principle, floating a bubble of water on compressed xenon. Can You Float a Liquid on a Gas?
Cody also breathes some xenon. His comment - "xenon hits you hard!". But your whales would have excellently low whale songs.
The short answer is no. The slightly longer answer is nooooooooooooo.
Things fly because they do one of these two things:
For the first strategy, you would have to attach something to the whale to get it to fly. Massive wings won't cut it; whales are just too heavy and too dense. They have a thick layer of blubber, whereas birds are nimble. Putting air pockets in the whale is not enough either, the creature itself is still too large. Larger flyers need exponentially bigger wings. The biggest flying dinosaurs were almost entirely wing, and even they could not lift off themselves: they would have to climb in a tree and glide.
To make a regular whale lighter than air, you would need a balloon many, many times larger than the whale. Think: the size of a stadium. You would barely see the creature. It does not matter whether you fill that balloon with helium, hydrogen or a pure vacuum, it's not nearly enough.
Both of these solutions would leave the resultant creature looking little like a whale.
And altering the planet? Making air dense enough for a whale to swim through, means essentially raising the water level, since a whale was designed to swim through water, not any gas. Gases are all far, far less dense than water.
Magic is your only bet. That, or a stash of negative mass, which is so theoretical it is essentially magic.
I'll be looking primarily at the second option.
How could we alter whales?
There's some links & resources in my answer to Hydrogen Dragons we can perhaps repurpose.
In particular : A cubic foot of hydrogen lifts around 30.8 grams (68 lbs per 1,000 cubic feet)
And I'll be looking at this in relation to the blue whale which is up to 30 m long.
We've dimensions for the blue whale here which suggest we can use a height of maybe 4.5 m for that 30 m length & it's roughly tubular so we can extrapolate that for the width a well, a bit rough & ready perhaps but it'll do for now.
The animal tapers a little at the rear & front so I'll go with 4 m x 4 m x 30 m, that gives us a volume of 480 cubic metres.
If we cut that to 440 cubic metres to allow for actual body mass (this whale dirigibles skin organs & other structures etc. then that's 15538.5 cubic feet of gas with a lifting capacity of 1056.62 pounds leaving you with 1412.59 cubic feet for the non gas volume (the organs & bones) of the animal.
You might find this useful for the conversions from cubic metres to cubic feet.
For reference :
Assumption : the given bone / meat ratio is by weight not volume, correct me if that's wrong.
So we've given ourselves 1056.62 pounds of weight that volume of hydrogen can lift & by the ratio above that's 295.85 pounds of bone & 760.76 pounds of flesh & muscle.
So that's
Bone : 134196.68 grams of bone / 1.9 = 70629.83 cm3
Meat : 345077.18 grams of meat / 1 = 345077.18 cm3
Total = 415707.01 cm3, which is 41.57 cubic metres.
Which for a rough concept outline is close enough to the 40 cubic metres we allowed for this.
In summary / So far.
What we have is a 30 m long 4 m wide 4 m deep cuboid (I was lazy should have done it as a tube, but I can't be bothered to go back & redo it so just go with it) consisting of around 1056.62 pounds (479.27 kilo or 0.53 US ton) of skin, flesh, bone & organs, all wrapped around 440 m3 of hydrogen.
That gives us a surface area of 512 m2 that we have to stretch 41.57 m3 of organic animal over.
If we squash our 40 m3 of flesh & bone into a 10x4x1 m cuboid (40 m3) & cut it into 10 m high by 4 m wide (40 m2) slices then 12.8 of them are needed to cover this surface & they'll be 7.81 cm thick.
Dang! suddenly this isn't sounding too plausible, never mind, just hang on & bear with me.
So let's halve that & assume an average skin (which may not be all 'skin') thickness of 3.9 cm, which will leave us with with 20 m3 of flesh & bone to play with for other organs & structures.
OK we can probably do this, but your whale is going to be a lot more fragile than a real whale.
What this means is you're whale can look more or less exactly like a whale & I can imagine it feeding on insect swarms & particulates in the air much as a whale in the ocean feeds on krill.
But the actual meat & bone by volume will be vastly decreased & it's liable to wallow through the air rather than fly & have difficulty flying against strong winds (in fact it probably can't).
Given the gas used for lift a flaming arrow may produce spectacular results if it pierces the skin.
Unfortunately, the laws of physics do not work in your favor here.
- How could we alter earth conditions (thickness, gravity) so that whales could fly actively (without changing anything in the animal)?
Keeping something with the mass and dimensions of even a small whale species in the air AND alive without external support is probably impossible no matter what the environment is. At minimum, it would require drastically increased air density and drastically decreased gravity compared to what is found on Earth. The difficulty increases with the size of the whale, because larger whales are so massive that their bodies are unable to support their own weight without support from buoyant forces in water.
You can't only change the gravity, because moving through air and water is very different and unmodified whales wouldn't be able to control their movement at normal atmospheric densities (compare the flying/swimming motions of birds and fish, or the designs of airplane and boat propellers).
Increasing the air density would introduce its own problems, however. You would need to change the atmospheric composition as well, because pretty much every breathable gas becomes narcotic and/or toxic at high pressures - see inert gas narcosis and oxygen toxicity. It is also questionable if lungs designed to breath air at sea level densities would be able to handle air at densities that allow swimming, though deep-diving whales probably are best-adapted to handle these last two problems as they already deal with extreme deep-sea pressures.
- How could we alter whales (change bones, physiology, anatomy, but leave size and appearance) so that they could fly in normally earth conditions?
This is much more doable in many ways, though it does still run into the issue that whales are not designed to achieve meaningful thrust and maneuverability in air. But we'll set that aside for the moment.
To make something the size and shape of a whale stay in the air unassisted, you need to make it a balloon (more specifically, an aerostat). In this case, you want to go as big as possible because of the square-cube law: if you double something's size, its surface area is multiplied by four while its volume is multiplied by eight.
The mass of a balloon depends on its surface area, while its lifting power depends on its volume, so compared to a one-foot-diameter balloon, a two-foot-diameter balloon weighs four times as much but can lift eight times the total mass of balloon-and-payload.
For a whale-blimp, the balloon is its skin and the payload is the rest of its organs. Everything in the whale needs to be as small and lightweight as possible, with the majority of its body containing only its lifting gas. That means minimal skeleton, minimal muscles, no blubber, and so on.
Getting back to the question of movement, you still can't swim through air and eliminating most of the muscles will do nothing to help with that. Movement will need to instead rely primarily on adjusting buoyancy to rise or sink into different winds like hot air balloons do, using the tail and flippers as small rudders for a (tiny) bit of extra control.
Consider something that can fly, which has about the same mass and generally unaerodynamic shape as a small whale.
For example a Robinson R44 helicopter. (https://en.wikipedia.org/wiki/Robinson_R44)
Sp how do we have to modify the whale to make it perform the same way? We don't necessarily need rotor blades, if the whale can produce a continuous vertical air jet somehow. But we do need a lot of energy.
An R44 burns about 1 liter of gasoline per minute to keep itself airborne, and gasoline is a very energy-dense fuel. So you need to change the metabolism of the whale to do something similar, and also provide it with a suitable "food source".
I can ask how superman flies through the air and how Superman propels himself though outer space.
Possibly Superman somehow has the power to generate artificial gravity fields to make himself "fall" toward where he wants to go.
And if some mad scientist inserts some sort of gravity control machines or organs into whales, whales might be intelligent enough to be taught and/or learn by themselves how to control that power and fly safely. After all there is a probability, however large or small, that some or all cetaceans may be as intelligent as humans and thus count as people, in real life.
And every other way that any science fictional character has "flown" though air or outer space without a vehicle or obvious mechanical propulsion in any science fiction story, novel, or comic, could theoretically be adapted for use by whales with approximately as much or as little plausibility as in the original story, novel, or comic.
