Answer:
A man shot two arrows at its center and missed both times, but using a sword swung once at its center and hit it twice.
It is weightless, you can see it. If you put it in a barrel it will make it lighter?
They're up near the sky, on something very tall. Sometimes they die, only then do they fall.
Talks like this, a green wise man does. Guess my clue, you will.
Born of earth, but with none of its strength. Molded by flame, but with none of its power. Shaped
You can always see it, but it's too far away to touch. Mountains rest on it, and at sea it surrounds you. What is it?