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Alfred_The_Sartan t1_jck6b4a wrote

Reply to comment by Gedankensortieren in What makes one greenhouse gas stronger at trapping heat than another? by sand_eater

Does size of a molecule play into how high in the atmosphere it can get? Like is it that the bigger ones get warmer and therefore rise like a box of legos or does the mass keep them generally lower due to gravity? I feel like I’m overthinking this and that the effects of molecular size to dispersion are negligible

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Gedankensortieren t1_jcktg3h wrote

I don't know. The only example I know is that helium and H2 are that lightweight that they can escape into space. Hence the molecular weight seems to play a role, but that's all I know.

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eotfofylgg t1_jclfjlr wrote

The atmosphere is full of wind, which keeps things pretty well mixed, at least in the troposphere.

In a hypothetical perfectly still atmosphere, the heavier molecules would tend to settle to the bottom. Even then, the air wouldn't be perfectly stratified like a layer cake, because there is enough thermal energy to mix the layers. But you would observe that, as the elevation increased, the concentration of heavier molecules dropped off faster than the concentration of lighter molecules.

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