# Hypothetical flying and gliding animals of planets with higher atmospheric pressure

 P: 78 How would they look like? Being more specific and less speculative: would higher atmospheric pressure (ex. 5 atm) mean that it is easier to fly/glide because lower wingspan would allow to achieve the same lift? Or it would be actually harder, because denser atmosphere would mean higher drag and flying would be actually more expensive in terms of calories? Assuming that the composition or atmosphere would be roughly comparable to Earth's with higher pressure that would mean proportionally more oxygen so more primitive breathing and blood system could be used. (or an advanced one could be much more efficient) Which would allow to burn calories quicker. Am I right? Assumptions: carbon chauvinism, so on molecular level life roughly similar to that known from Earth.
 P: 3,091 denser atmosphere means stronger gravity. So you could figure out how strong gravity would be to get 5 atm pressure.
 P: 53 It could be harder to fly because of the force made by the denser air. Those animals, would be mostly small if the atmosphere has nutrients that can be extracted. The largest, more developed animals could be of the size of a butterfly and they could fly no higher than 3-4 meters.
P: 741
Hypothetical flying and gliding animals of planets with higher atmospheric pressure

 Quote by jedishrfu denser atmosphere means stronger gravity. So you could figure out how strong gravity would be to get 5 atm pressure.
Gravitational force and an atmospheric density are not strongly correlated. Earth an Venus together make a good counterexample to your hypothesis. Venus and earth have about the same mass, but the atmospheric density at the surface of Venus is much higher than the atmospheric density on the surface of the earth.

Atmospheric density depends on the availability of gas, temperature and gravitational force. One result is that atmospheric density can also vary with geologic time. The atmosphere of Mars may have been much denser than it is now. The density may have changed with time. When the temperature rises, the ice cap evaporates. That provides a thicker atmosphere.

The earth itself may have undergone changes in atmospheric density. Hotter climate can lead to more water vapor can lead to greater atmospheric pressure. Biological processes can add or take gases out of the atmosphere.

Mesozoic animals may have flown in a denser atmosphere than animals in the Cenozoic. I suspect that this is driving the OP's question.

The time it takes for an atmosphere to diffuse away from the planet can be very long over a large range of gravity and pressure. So changes in the availability of gas can drive changes in atmospheric density.

Here is a link to an article showing how the atmospheric density of a planet may vary with time. Unfortunately, the link contains only the abstract.
http://www.scientificamerican.com/ar...ir-atmospheres
“A planet can acquire a gaseous cloak in many ways: it can release vapors from its interior, it can capture volatile materials from comets and asteroids when they strike, and its gravity can pull in gases from interplanetary space. But planetary scientists have begun to appreciate that the escape of gases plays as big a role as the supply.”
 P: 3,091 I was thinking that if you kept all things equals and change the gravity to create 5atms then you could deduce how the wingspan would change.
P: 741
 Quote by Czcibor How would they look like? Being more specific and less speculative: would higher atmospheric pressure (ex. 5 atm) mean that it is easier to fly/glide because lower wingspan would allow to achieve the same lift? Or it would be actually harder, because denser atmosphere would mean higher drag and flying would be actually more expensive in terms of calories? Assuming that the composition or atmosphere would be roughly comparable to Earth's with higher pressure that would mean proportionally more oxygen so more primitive breathing and blood system could be used. (or an advanced one could be much more efficient) Which would allow to burn calories quicker. Am I right? Assumptions: carbon chauvinism, so on molecular level life roughly similar to that known from Earth.
Here is a quantitative analysis. Density would decrease the power necessary for flight.
“A variation in weight and atmospheric density does not yield a change in motion but has
an impact on the required power.”

Here is a speculation that suggests that you are right.
http://en.wikipedia.org/wiki/Colonization_of_Titan
“The very high ratio of atmospheric density to surface gravity also greatly reduces the wingspan needed for an aircraft to maintain lift, so much so that a human would be able to strap on wings and easily fly through the atmosphere.”

There is a theory that higher atmospheric density during the Mesozoic may have made pterosaur flight possible. However, some scientists don’t believe that is the case.
http://pterosaur-net.blogspot.com/20...ifference.html
“A slight increase in atmospheric density would have relatively little impact on the maximum size of dinosaurs or pterosaurs, however, and there is not actually any need for an extreme explanation for their size, anyway - despite being larger than living animals with similar lifestyles, none of the giant dinosaurs exceeded the expected maximum size for a walking animal, and no pterosaurs exceeded the limits for biological flight. Quite a few pterosaurs exceeded the estimated limit for continuous flapping flight in a vertebrate animal (limit is roughly 25-30 kg, give or take), but that only means that they could not flap continuously over long distances and would have switched to soaring flight for long trips; it does not forbid them from flying.”

Note that on earth, changes in the percentage of oxygen could have impacted biology as much or greater than the changes in atmospheric pressure alone. An animals would have much more power available in an atmosphere loaded with oxygen, independent of pressure.

The two, oxygen and density, could vary independently. Separating the effects of one as opposed to the other could be difficult.
P: 78
 Quote by Darwin123 Here is a quantitative analysis. Density would decrease the power necessary for flight. http://gradworks.umi.com/3382955.pdf “A variation in weight and atmospheric density does not yield a change in motion but has an impact on the required power.” Here is a speculation that suggests that you are right. http://en.wikipedia.org/wiki/Colonization_of_Titan “The very high ratio of atmospheric density to surface gravity also greatly reduces the wingspan needed for an aircraft to maintain lift, so much so that a human would be able to strap on wings and easily fly through the atmosphere.” There is a theory that higher atmospheric density during the Mesozoic may have made pterosaur flight possible. However, some scientists don’t believe that is the case. http://pterosaur-net.blogspot.com/20...ifference.html “A slight increase in atmospheric density would have relatively little impact on the maximum size of dinosaurs or pterosaurs, however, and there is not actually any need for an extreme explanation for their size, anyway - despite being larger than living animals with similar lifestyles, none of the giant dinosaurs exceeded the expected maximum size for a walking animal, and no pterosaurs exceeded the limits for biological flight. Quite a few pterosaurs exceeded the estimated limit for continuous flapping flight in a vertebrate animal (limit is roughly 25-30 kg, give or take), but that only means that they could not flap continuously over long distances and would have switched to soaring flight for long trips; it does not forbid them from flying.” Note that on earth, changes in the percentage of oxygen could have impacted biology as much or greater than the changes in atmospheric pressure alone. An animals would have much more power available in an atmosphere loaded with oxygen, independent of pressure. The two, oxygen and density, could vary independently. Separating the effects of one as opposed to the other could be difficult.
Thanks!
P: 53
 Quote by Darwin123 Here is a quantitative analysis. Density would decrease the power necessary for flight. http://gradworks.umi.com/3382955.pdf “A variation in weight and atmospheric density does not yield a change in motion but has an impact on the required power.” Here is a speculation that suggests that you are right. http://en.wikipedia.org/wiki/Colonization_of_Titan “The very high ratio of atmospheric density to surface gravity also greatly reduces the wingspan needed for an aircraft to maintain lift, so much so that a human would be able to strap on wings and easily fly through the atmosphere.” There is a theory that higher atmospheric density during the Mesozoic may have made pterosaur flight possible. However, some scientists don’t believe that is the case. http://pterosaur-net.blogspot.com/20...ifference.html “A slight increase in atmospheric density would have relatively little impact on the maximum size of dinosaurs or pterosaurs, however, and there is not actually any need for an extreme explanation for their size, anyway - despite being larger than living animals with similar lifestyles, none of the giant dinosaurs exceeded the expected maximum size for a walking animal, and no pterosaurs exceeded the limits for biological flight. Quite a few pterosaurs exceeded the estimated limit for continuous flapping flight in a vertebrate animal (limit is roughly 25-30 kg, give or take), but that only means that they could not flap continuously over long distances and would have switched to soaring flight for long trips; it does not forbid them from flying.” Note that on earth, changes in the percentage of oxygen could have impacted biology as much or greater than the changes in atmospheric pressure alone. An animals would have much more power available in an atmosphere loaded with oxygen, independent of pressure. The two, oxygen and density, could vary independently. Separating the effects of one as opposed to the other could be difficult.
Interesting content! Hope Titan is terraformed someday and Earth species are brought and evolved there
 P: 390 Some short and simple quantitative analyses: If the pressure and density of atmosphere are increased 4 times then, yes, the drag for the same size and speed would increase 4 times. But so would lift, and the weight would be nearly unchanged. Water is about 800 times denser than air. Many waterbirds - all of them small - manage to fly in both water and air. Obviously they are slower in water than in air. Note that not all diving birds fly in water - many fold their wings in water and swim with webbed feet instead. If you increase the pressure and density of air 4 times, a bird of given weight and size would be able to support its weight by flying at a 2 times slower speed. While the drag would be unchanged, it would be developing only half the power needed to fly on Earth - it would expend same amount of energy to fly the same distance, but it would have twice as long time to do so - and therefore it could do with weaker heart, and possibly lungs. Alternatively, the bird could fly at the same speed, but have 4 times smaller wing area, or half the wingspan, for the same weight. Shorter wings would be mechanically easier and stronger. Again compare with water. While swimming animals are generally slower than flying animals, some of them are quite fast. Tunnies, dolphins, penguins... The fast swimmers are stocky and muscular. Their relatively short but strong flippers could not lift their weight into thin air, but are useful in water. In 4 atm air, the contrast between water and air density would be only 200 times, not 800 times. So it would be easier for waterbirds to adapt to both air and water. Regarding oxygen: at 0,13 bar oxygen in lungs, 100 ml human blood contains 20 ml oxygen in hemoglobin, but just 0,3 ml in water solution. Increasing oxygen partial pressure a few times would not significantly improve oxygen supply.

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