They don’t float because that’s not possible.
Frozen clouds over Mann’s planet is a known flaw of this movie.
Nolan wanted them clouds for the eye. So they had taken some creative liberty there.
The physicist who consulted on this movie was Kip Thorne and he wrote a book about the science of the voyage.
The book told the true stuff. The clouds were fake things, he admitted.
Ice shards hard things, has more heft than the sky.
Hard earth would take them.
And there's no making high shapes in the sky.
Only about the black deeps and the time; the movie mostly speaks right about.
Nonetheless the white planet is still wrong.
In the dark seats the people watching a strange wonder that was made only for the movie but all those hefty clouds would come down.