Like clouds

Ideas should be like clouds:
there one day, gone the next,
always returning.
Causing us to wonder,
to find intriguing shapes
soon burnt away by the sun.
No matter how many we see,
each one is different.
Some provide a moment's shade,
others rain the bounties of heaven.
They connect without seams --
innumerable, yet one in substance.
Never impeding flight,
sometimes touching the earth,
obscuring, yet informative.
And when their time is up,
they are gone.