Which mechanism initially constrained the operational altitude of early hot air balloons?

💡 Explanation

When ascending, atmospheric pressure decreases, leading to lower oxygen partial pressure, causing hypoxia in the balloonists. Therefore pilot hypoxia was the limit, rather than fabric tearing, burner failure, or rope breakage which would depend on structural or fuel constraints, independent of altitude.

• Which agricultural adaptation helped pre-Columbian civilizations cultivate maize in arid highland regions?
• Which risk increases when differential settling occurs in the foundations of a Mesopotamian ziggurat?
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• Which environmental risk increases with maize monoculture farming on pre-Columbian chinampa systems?
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• Which consequence results from prolonged exposure to seawater for wrought iron components in a Roman ballista?