Answer:
What is it which builds things up? Lays mountains low? Dries up lakes, and makes things grow? Cares not a whim about your passing? And is like few other things, because it is everlasting?
I'm light as a feather, yet the strongest man can't hold me for more than 5 minutes.
We travel much, yet prisoners are, and close confined to boot. Yet with any horse, we will keep the pace, and will always go on foot.
The man who invented it doesn't want it. The man who bought it doesn't need it. The man who needs it doesn't know it. What is it?
I have a neck but no head. I have a body but no arm. I have a bottom but no leg.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.