Answer:
It is a path of cow juice spread across the sky but cannot be seen by the naked eye
It cannot be seen, it weighs nothing, but when put into a barrel, it makes it lighter.
Although my cow is dead, I still beat her. What a racket she makes!
I am nothing really at all, Yet I am easily foundΝΎ Ignore me at your own peril, and you might end up crowned!
There are millions of me. I am very small but when moving fast I am deadly.
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.