Answer:
I turn around once. What is out will not get in. I turn around again. What is in will not get out.
Fatherless and motherless. Born without sin, roared when it came into the world. And never spoke again.
Two brothers we are, great burdens we bear. All day we are bitterly pressed. Yet this I will say, we are full all the day, and empty when go to rest.
I fly, yet I have no wings. I cry, yet I have no eyes. Darkness follows me. Lower light I never see.
You throw me out when you want to use me and you take me in when you don't want to use me. Who am I?
I’m grown from darkness but shine with a pale light. Very round I am and always a lady's delight.