E Pericoloso Sporgersi wrote:voralfred wrote:E Pericoloso Sporgersi wrote:orchestrali wrote:That would be number 2, Hydrogen, of course! ...
I'm itching to answer, it is even stronger than just an itch… Other players, beware!
I know you like explaining things (like the good Dr. Isaac Asimov used to do).
So please, in passing, also tell us why molecular hydrogen gas,
H2, at the same pressure and temperature as Sergyar's atmosphere, is the one and only gas that can provide boyancy to airborne living creatures.
(I assume that deuterium and tritium are too rare to be used by living organisms.)
Well, in fact, LMB decided it had to be molecular hydrogen
H2. However, your proposal of methane
CH4 was quite interesting. Methane is
much easier for living organisms to produce than molecular hydrogen. Just ask cows (or, rather, their intestinal flora)! It is flammable, maybe not quite as explosively as
H2, but enough to destroy the creatures if a live flame is brought in contact with them, so Aral and Cordelia could still have disposed of them the same way. And its buoyancy is just about half that of
H2 : at any given temperature and pressure, the respective buoyancy of various gases is proportional to 29 (mean molecular mass of air, on Earth but also probably on Sergyar) minus the molecular mass of the gas under consideration, 29-16=13 for
CH4 vs 29-2=27 for
H2. This reduction, however, is more than compensated, IMHO, by the ease to produce methane versus the huge metabolic cost of producing hydrogen.
Helium is almost as buoyant as
H2 (29-4=25 vs 27) but is very rare, and hard for living organisms to separate out of air. Separating isotopes like deuterium or tritium out of natural hydrogen (which contains a little deuterium and very, very little radioactive tritium) is almost impossible for living organisms and what would be the point? Besides
CH4, the only gas with significant buoyancy I can think of is ammonia
NH3, but it is harder to make than
CH4 (though easier to produce than
H2) but, more importantly, it has a strong affinity for water, so it would tend to dissolve into the creatures tissues instead of filling a cavity as
CH4 would. At higher temperature, there is water vapor, of course, but then the beasties would have to be boiling ! So I'd say,
CH4 would have been my choice. But then, I did not write _SoH_... !