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I answered this question by theorizing that making a world's atmosphere thinner at sea level could limit the viability of airplanes used in naval warfare. My reasoning was that a thinner atmosphere would make it harder for planes to take off, requiring a longer runway (less feasible for aircraft carriers) and/or redesigned planes (which could limit effectiveness).

I'm curious about how else a thinner atmosphere might affect warfare on a planet from WWI-era to late Cold War-era technology. Some things that come to mind for me are:

  • Chemical weapons would stay closer to the ground due to lower air density.
  • Bullets and artillery may go farther due to lack of air resistance (or perhaps not due to aerodynamic limitations).
  • Most airplanes, at least earlier on in the century, would fly much closer to the ground and therefore be in closer range of guns because of difficulty getting lift at higher altitudes.
  • Airplanes would have a harder time getting into the air and might require redesigns (such as carrying less explosives or having larger wings).
  • Perhaps fires wouldn't burn as long due to the thinner atmosphere.

I am presuming that the human-like civilization that evolved on such a planet would have adapted to a thinner atmosphere and would not have difficulty breathing as humans would in a thin atmosphere.

Is my reasoning correct or am I incorrect about some of my assumptions? Are there other dramatic ways warfare would be affected that I'm not thinking about?

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closed as too broad by sphennings, Josh King, kingledion, L.Dutch, adaliabooks Dec 16 '17 at 11:07

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Also: I am not familiar with the tags on this Stack Exchange so if someone knows some that better fit the question, please suggest them! $\endgroup$ – Rob Rose Dec 15 '17 at 21:22
  • $\begingroup$ Do you consider thinner atmosphere to be equally thin in oxygen, or oxygen concentration would be increased to compensate for the lower pressure? $\endgroup$ – Alexander Dec 15 '17 at 21:31
  • $\begingroup$ Warfare differed a lot over the course of the 20th century. Perhaps it would be a good idea to reduce the scope of the question. $\endgroup$ – sphennings Dec 15 '17 at 21:31
  • $\begingroup$ @Alexander Originally I was thinking that it would be equally thin in oxygen, but allowing it to compensate for lower pressure could be interesting. Unfortunately, I don't know how feasible that is because oxygen is heavier than nitrogen, and a higher oxygen concentration would be toxic I believe. I think it requires fewer modifications to human biology to simply say that lungs are more efficient at extracting oxygen than that oxygen concentrations are the same. I am not sure though, as I am not a biologist. $\endgroup$ – Rob Rose Dec 15 '17 at 21:53
  • $\begingroup$ @sphennings I would argue though that 20th century warfare is one continuous chain of technological development as experiences in WWI shaped WWII which in turn shaped the Cold War. I'm interested in the whole timeline but if no one answers after a while I'll probably limit the scope to WWI through the Korean War-era. $\endgroup$ – Rob Rose Dec 15 '17 at 21:57
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You're thinking too small. Everything has changed not just warfare.

Thinner atmosphere means that fires don't burn as hot and it is now very difficult, if not impossible, to work with metal. I'm talking basic metal working as in making plowshares, never mind armour, swords or spears.

Can you shape the metal you'll need for your airplane engines ? Aviation fuel won't burn as hot, you'll need petrol and you'll need to carry more of it.

Would bullets work ? I know modern bullets have oxidising agents in the gunpowder but that wasn't always the case. How would your society get to that point in weapons tech if everything they've experienced shows that gunpowder is (pardon the pun) a bit of a damp squib ?

A lot chemical reactions are pressure dependant, their chemical and biological scientific development would take quite a different path to ours.

Everything has changed.

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  • $\begingroup$ "fires don't burn as hot" - temperature of the flame does not depend on the pressure, only on ratio of oxygen and fuel used. $\endgroup$ – Vashu Dec 16 '17 at 8:52
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    $\begingroup$ "modern bullets have oxidising agents in the gunpowder but that wasn't always the case" - gunpowder have to burn too fast to react with any noticeable amount of atmosphere oxygen. So that was always the case. $\endgroup$ – Vashu Dec 16 '17 at 9:28
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I am going to assume that we halve density of the atmosphere. Atmosphere with half the pressure would be equivalent to our atmosphere at 4 km - there are towns on Earth above this level, so it is possible for a human to adapt to this.

Fire would actually burn longer, as it would take longer to deliver same amount of oxygen to the fuel.

Infantry and horses would move slower, as they would spend more effort on breathing. It would make firearms more effective - defenders would have more time for firing. Bullets would go father, but efficient range for typical infantry only some hundreds meters so it would not matter much.

Artillery would reach much father. For example 3 inch gun with 20 degrees elevation would reach only about 10 km, in vacuum it would be 30 km! So even halving the density would add many kilometers.

Shell and grenade pieces would reach much father as well.

Service ceiling of typical WWI fighter is about 6 km so WWI level aircraft would be useless for bombing. But with WWII level of technology aviation would turn into a formidable opponent.

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