Wind

'It issues from the tops of trees
born from the gyrations of their limbs
from there it flies straight to the equator,
circumnavigates the globe, then goes on
to generate the tides...'

What? Stop the video. That's ridiculous!

Not scientific really,
but a plausible theory;
when you don't know what's what, just
take care whose opinion you trust:
Earth, once viewed as flat, is round
and Truth, a powerful sound-
but doubt makes Truth honest.