Riddle Me That

I surround you for about half the day, then the other I am banished.
I overwhelm you and scare you but shine a light and I've vanished.

In ways I am peaceful and I'm not at all scary if you stop and think.
I happen every time that you are not looking and blink.

I don't just come out at night time I can be found in so many places.
Under the bed, in wardrobes, cubboards and in closed cases.

I am not something you can touch at all and I am not hot or cold.
I lack in colour and brightness because I am not loud or bold.

I don't actually exist I'm just a lack of something much bigger.
I'm sure by now you've worked me out? If not... Go figuer!