Eli5 what controls if a gas is heavy or not? Example helium Seems to defy gravity while something like xenon I assume would sink
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This 9 bound bowling ball defies gravity. I pushed it to the bottom of my swimming pool, and it just floats straight on up! I thought gravity pushed things down!
When surrounded by other things (air, water, etc) pressing against it, the denser/thicker stuff will sink to the bottom at the expense that the lighter/thinner stuff will be forced to rise upwards. Helium is close to the lightest gas that exists so of course it will want to go up. Xenon is actually quite heavy as an atom and will want to go down. These need to be compared to normal air, which is mostly nitrogen and oxygen, and the difference is very significant.
Hot air balloons take advantage of the same strategy, except that hot air is also thinner than normal/cold air. So a big bag of hot air (and I mean really big bag) will weigh less than a big bag of cold air and float upwards. Then we just tie something to it and go for a ride. Same idea, different technique.
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