You cannot always see me, but I'm always there
I am frequently harsh, causing destruction and grief
I have many moods, and can change in a second
I can hurt you and scare you and make people hide
I am talked about all over the world
I have programmes dedicated just to me
People are fascinated by me, following my stories
I am always there, every second of every day.. forever
I cannot be killed, injured or altered
You cannot touch me or converse with me
I can trick you and tease you.. and frequently do
Even the experts who study me their whole lives.. still do not understand me at times
What am I?