Absolutely nothing. Planes do it all the time. And sometimes if you go up in the mountains the clouds will be low enough you can touch them.
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It'd be almost exactly like going through fog. So if you've ever been in fog, there you have it.
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gravity would continue to pull you down to earth, where you would go splat.
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Pot of marshmallows on the other side.
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its one of those things you have to do to really know the answer