3 ms·

You won't see any wings on a hot air balloon. If you think it is not common, look at the fish in the ocean.

by d0mine 5y ago

autokad 5y ago
now you have de-evolved the conversation by trying to change the definition of fly to swim. if you are going to do that, there is no point in continuing the discussion. Furthermore, you are confusing buoyancy with flight.
- d0mine 5y ago
  Both air & water are fluids (same equations can be applied to many problems). Equating them in the discussion about aliens is not a step too far which it doesn't require much imagination (compare it for example with an idea of a living nebula that might require some knowledge what is entropy, what is life in terms information, etc)
giantrobot 5y ago
You don't see a lot of natural hot air balloons floating around do you? Buoyancy in water is different than in air. Lighter than air natural controlled flight, even in a relatively dense atmosphere like Earth or Titan, is highly unlikely. Fish maintain buoyancy with oil in their livers which is a relatively low energy process. Hot air balloons and other LTA vehicles work by having a mean density lower than the containing medium e.g. the atmosphere. Even with Earth's relatively dense atmosphere there's not a lot of lifting gases that are effective without significant heating. Definitely not readily made by biological chemical processes. That leaves thermal balloons. The amount of energy to heat the air in a hot air balloon is pretty significant and requires energy dense fuels. So a hot air balloon animal would need to produce and then burn energy dense hydrocarbons and have a strong yet lightweight natural gas envelope and body structure that could handle the burning of that fuel. Burning I would note at temperatures that would sterilize surfaces.
- gambiting 5y ago
  >>You don't see a lot of natural hot air balloons floating around do you? Not balloons perhaps, but spiders float on strands of silk using very similar principles. Pollen and seeds frequently use some kind of floating device to spread as far as possible - again, you probably wouldn't call it flying as such, but they can move through the air for the purposes of reproduction without having wings.
  - giantrobot 5y ago
    Floating is not controlled flight. Being blown by the wind due to a high surface area to weight ratio is not flight. I move through the air without wings when I walk. I could jump off a diving board and get some forward motion going. Neither are in any way flight.
    - ncmncm 5y ago
      Anyway, balloons or no, there is a great deal of hot air.
- ncmncm 5y ago
  1. Fish do not, in fact, use oil in their livers for buoyancy. They have an "air bladder", which you may read about. You might have heard something, somewhere about shark livers. Fish are much more closely related to you than to sharks, so it is a big error. 2. Buoyancy in air has been achieved with an industrial level of success using hydrogen. Producing hydrogen is easily within the energetic range of biological processes. Air-buoyant animals could have existed for millions, even hundreds of millions of years before being outcompeted by pterosaurs and birds, and then left no trace.
  - dragonwriter 5y ago
    > Fish are much more closely related to you than to sharks Sharks are fish, so this clearly isn't categorically true. You probably mean either bony fish (for which I think it's kind of questionable that its true) or more specifically lobe-finned fish (for which the case is stronger.)

You won't see any wings on a hot air balloon. If you think it is not common, look at the fish in the ocean.

by d0mine 5y ago

You won't see any wings on a hot air balloon. If you think it is not common, look at the fish in the ocean.

now you have de-evolved the conversation by trying to change the definition of fly to swim. if you are going to do that, there is no point in continuing the discussion. Furthermore, you are confusing buoyancy with flight.

d0mine 5y ago
Both air & water are fluids (same equations can be applied to many problems). Equating them in the discussion about aliens is not a step too far which it doesn't require much imagination (compare it for example with an idea of a living nebula that might require some knowledge what is entropy, what is life in terms information, etc)

giantrobot 5y ago

You don't see a lot of natural hot air balloons floating around do you? Buoyancy in water is different than in air. Lighter than air natural controlled flight, even in a relatively dense atmosphere like Earth or Titan, is highly unlikely. Fish maintain buoyancy with oil in their livers which is a relatively low energy process. Hot air balloons and other LTA vehicles work by having a mean density lower than the containing medium e.g. the atmosphere. Even with Earth's relatively dense atmosphere there's not a lot of lifting gases that are effective without significant heating. Definitely not readily made by biological chemical processes. That leaves thermal balloons. The amount of energy to heat the air in a hot air balloon is pretty significant and requires energy dense fuels. So a hot air balloon animal would need to produce and then burn energy dense hydrocarbons and have a strong yet lightweight natural gas envelope and body structure that could handle the burning of that fuel. Burning I would note at temperatures that would sterilize surfaces.

gambiting 5y ago
>>You don't see a lot of natural hot air balloons floating around do you? Not balloons perhaps, but spiders float on strands of silk using very similar principles. Pollen and seeds frequently use some kind of floating device to spread as far as possible - again, you probably wouldn't call it flying as such, but they can move through the air for the purposes of reproduction without having wings.
- giantrobot 5y ago
  Floating is not controlled flight. Being blown by the wind due to a high surface area to weight ratio is not flight. I move through the air without wings when I walk. I could jump off a diving board and get some forward motion going. Neither are in any way flight.
  - ncmncm 5y ago
    Anyway, balloons or no, there is a great deal of hot air.
ncmncm 5y ago
1. Fish do not, in fact, use oil in their livers for buoyancy. They have an "air bladder", which you may read about. You might have heard something, somewhere about shark livers. Fish are much more closely related to you than to sharks, so it is a big error. 2. Buoyancy in air has been achieved with an industrial level of success using hydrogen. Producing hydrogen is easily within the energetic range of biological processes. Air-buoyant animals could have existed for millions, even hundreds of millions of years before being outcompeted by pterosaurs and birds, and then left no trace.
- dragonwriter 5y ago
  > Fish are much more closely related to you than to sharks Sharks are fish, so this clearly isn't categorically true. You probably mean either bony fish (for which I think it's kind of questionable that its true) or more specifically lobe-finned fish (for which the case is stronger.)