What is always in front of you but can’t be seen?

Can anyone tell me a word in the English dictionary which has a silent 'z'?

What runs around the whole yard without moving?

What is at the end of a rainbow?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

What goes up but never comes down?

What word is pronounced the same if you take away four of its five letters?

Living above a star, I do not burn
Eleven friends and they do not turn
I can just be visited in a sequence, not once or repeatedly
PQRS are my initials
Can you tell my name accurately?