Answer:
What is not a ball but yet a sphere, and holds all lands and people year after year?
They come to witness the night without being called, a sailor's guide and a poet's tears. They are lost to the sight each day without the hand of a thief.
If you are unsure how to use one then just ask a flight attendant.
You do this into someone's ear when you want to be discreet.
I start in little but I end in full, you'll find me in half and complete.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.