What am I?

I was known to Greek philosophers a thousand years ago, I have numbers all in a line, and I can tell you if rain will turn to snow. What am I?

Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls. What am I?

We hurt without moving. And poison without touching. We bear truth and lies, But are not judged by size. What are we?

You may enter, but you may not come in, I have space, but no room, I have keys, but open no lock. What am I?

Riddles and Answers