What Am I Riddles

Question: I can be shared by many or spread to few, I am as fragile as silk yet as strong as steel. Wars have been fought in my name, generations defined by me. What am I?

Question: Until I am measured, I am not known. Yet how you miss me, When I have flown What am I?

Question: I sit high glowing and watch the world go by, without me everything would seem dull and dangerous. What am i?

Question: What can you see but not hear?

Question: What has classes but moves?