Answer:
When a doctor hits you with a hammer he is testing this
A mechanism to discover who is following you.
Old people and owls are said to be this.
Glittering points that downward thrust. Sparkling spears that do not rust. What is it?
I occur twice in eternity. And I'm always within sight.
How can you tell when a mummy has a cold?
Easy
Animal
Difficult
Food
Funny
Kids
Logic
What am I?