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In aeronautics, a balloon is an unpowered aerostat, which remains aloft or floats due to its buoyancy. It may use hot air as a lifting gas, or it may use gas that is not air like hydrogen or helium. A balloon may be free, moving with the wind, or tethered to a fixed point. It is distinct from an airship, which is a powered aerostat that can propel itself through

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