Good Riddles

Question: I cannot be seen, cannot be felt,
Cannot be heard, cannot be smelt.
I lie behind stars and under hills,
And empty holes I fill.
I come first and follow after,
End life, kill laughter.

What am I?

Question: What temperature is twice as hot as 0 degrees Celsius?

Question: What has 4 fingers and a thumb, but is not living?

Question: Samuel was out for a walk and it started to rain. He did not have an umbrella and he wasn't wearing a hat. His clothes were soaked, yet not a single hair on his head got wet.

How could this be?

Question: I am a cave full of bones,
and the house of a worm.

What am I?