Answer:
Sometimes I fly as fast as the speed of light. Sometime I crawl as slow as a snail. Unknown until I am measured but you will certainly miss me when Iām gone.
What goes up a chimney down but can't go down a chimney up?
I run up and down the stairs without moving. What am I?
What can fill a room but takes up no space?
The more you take of me the more you leave behind.
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.